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HF MESSAGING SYSTEM WITH AUTOMATIC LINK ESTABLISHMENT

(ALE) CAPABILITY

NURULFADZILAH BT HASAN

A thesis submitted in fulfilment of the

requirements for the award of the degree of

Master of Engineering (Electrical)

Faculty of Electrical Engineering

Universiti Teknologi Malaysia

JANUARY 2006



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I declale tlat this thesis entitled "HF Messaging Systen With Automatic Link

Establishnent (ALE) Capability" is the rcsnlt ofmy own researchexceptascited irl

the references. The thesis has not been accepted for any degree and is not

concunently submitted n candidatueof any other degree.

Author : Nurulfadzilah Bt Hasan

Date : 16January 006



iii

Dedicated to my beloved husband and parents

Thank you for the inspirations



iv

ACKNOWLEDGEMENT

First and foremost the greatest praise to Allah for the blessings, guidance and

for the gift of courage for me to accomplish this research.

Highest gratitude and appreciation goes to my supervisor, Assoc. Prof. Dr.

Ahmad Zuri Sha’ameri, Thank you for the invaluable guidance, support, knowledge

and advices given to me throughout this study. I would also like to thank En. Wan

Roz for the priceless help and information he gave to make me better understand this

research.

To En. Jeffri Ismail, DSP lab technician, I would like to thank him for his

technical assistance throughout my study. Also, special thanks to Rahim, Sazali and

Fong Fong for helping me complete the field-testing for this research. To my friends

who are always there for me, thank you so much.

Finally, I would like to express endless appreciation to my family for their

love, patience and prayers.



v

ABSTRACT

HF radio spectrum, ranging from 3 to 30 MHz can be utilized for voice and

data communication. One of the benefit of using HF for communicating is that HF

system is low-cost, requires minimum equipments and easy to set up. But due to the

unpredictability and propagation problems such as multipath fading, interference and

attenuation, communication using HF becomes very challenging. Besides, the

availability of the channels varies depending on the time of day, seasons and the

condition of the ionosphere. The purpose of this research is to design a HF

messaging system equipped with Automatic Link Establishment (ALE) capability.

ALE is an adaptive radio technology for automatically establishing communications

over HF single sideband (SSB) links using the best frequency possible. The objective

of the research is to design a messaging system that permits reliable data

transmission over the HF radio with minimum cost and equipments. This research

also looked at the feasibility of implementing ALE as software, designed using

Visual C++ programming language. Equipments used in this research are

commercial HF radio and modem, which are both controlled by the software. Field

testing is conducted between UTM Skudai and several places in Malaysia to verify

the performance of the system. From the results, it is proven that by applying

adaptive radio technology, propagation problems can be overcome and reliability of

data transmission can be improved. Moreover, amateur radio users can use the

system, as it requires minimum equipment.



vi

ABSTRAK

Spektrum radio berfrekuensi tinggi atau HF iaitu dari 3 hingga 30 MHz boleh

digunakan untuk komunikasi suara dan juga data. Salah satu kebaikan menggunakan

HF ialah ia memerlukan kos yang rendah, memerlukan peralatan yang minimum dan

mudah untuk dibangunkan. Tetapi disebabkan keadaan HF yang sukar dijangka dan

masalah perambatan seperti multipath fading, gangguan dan pelemahan isyarat

menjadikan komunikasi menggunakan HF mencabar. Selain itu, kebolehan sesuatu

frekuensi bergantung kepada faktor masa, musim dan keadaan lapisan ionosfera.

Tujuan kajian ini adalah untuk membina sebuah sistem pesanan HF yang dilengkapi

dengan kebolehan capaian pautan secara automatik (ALE). ALE merupakan

teknologi radio ubah suai yang digunakan untuk menghasilkan jaringan komunikasi

dalam jalur tunggal (SSB) HF menggunakan frekuensi yang terbaik. Objektif kajian

ini adalah untuk menghasilkan sistem pesanan HF yang membolehkan penghantaran

data melalui HF dilakukan dengan baik menggunakan kos serta peralatan yang

minimum. Kajian ini juga bertujuan mengkaji kesesuaian menghasilkan ALE dalam

bentuk perisian, yang dibangunkan menggunakan bahasa pengaturcaraan Visual

C++. Peralatan yang digunakan dalam kajian ini adalah radio HF dan modem HF

komersil yang mana keduanya akan dikawal oleh perisian yang dinyatakan tadi.

Kajian lapangan diadakan antara UTM Skudai dan beberapa tempat di Malaysia

untuk menguji prestasi sistem tersebut. Keputusan yang diperolehi dapat

membuktikan bahawa dengan menggunakan teknologi radio mudah ubah suai,

masalah perambatan dapat diatasi dan kebolehpercayaan penghantaran data

ditingkatkan. Malah, sistem tersebut dapat digunakan oleh pengguna radio amatur

kerana ia memerlukan peralatan yang minimum.



vii

TABLE OF CONTENT

CHAPTER TITLEPAGE

ACKNOWLEDGEMENT ivABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLES xi

LIST OF FIGURES xiii

LIST OF SYMBOLS xvii

LIST OF ABBREVIATIONS xviii

LIST OF APPENDICES xx

1 INTRODUCTION

1.1 Background

1.2 Objective

1.3 Problem Statements

1.4 Scope of Study

1.5 Research methodology

1.6 Thesis Outline

1

2

3

4

4

5

2 LITERATURE REVIEW

2.1 Introduction

2.2 The Ionosphere

2.2.1 Variations of the Ionosphere

2.3 HF Radio Propagation

2.3.1 Multipath Effects on HF Propagation

7

8

10

12

14



viii

2.4 Automatic and Adaptive HF Communication System

2.5 Recent Developments in HF ALE Messaging

2.6 Summary

16

17

19

3 FREQUENCY PREDICTION FOR HF

COMMUNICATION

3.1 Introduction

3.2 Types of Frequency Prediction

3.3 Ionospheric Measurement

3.3.1 Ionograms

3.3.2 MUF and LUF Calculations

3.4 Important Factors in Frequency Prediction

3.4.1 Ionospheric Models

3.4.2 Geometry of The Circuit

3.4.3 Ionospheric Index

3.4.4 Other Parameters

3.5 Advanced Stand-Alone Prediction System (ASAPS)

3.5.1 ASAPS GRAFEX Frequency Prediction

3.5.2 ASAPS Field Strength Prediction

3.5.3 Frequency Prediction for UTM Skudai-Kota

Bahru Circuit

3.5.4 Frequency Prediction for UTM Skudai-

Chemor Circuit

3.6 Summary

20

21

21

22

23

24

24

25

25

26

27

27

30

30

34

37

4 AUTOMATIC LINK ESTABLISHMENT (ALE)

4.1 Introduction

4.2 ALE Protocols and Operational Rules

4.2.1 ALE Signal Structure

4.2.1.1 Word Structure

39

40

42

43



ix

4.2.1.2 Coding

4.2.1.3 Frame Structure

4.2.2 Calling Protocol

4.2.3 Scanning

4.2.4 Sounding

4.2.5 Link Quality Analysis (LQA)

4.2.6 Automatic Channel Selection

4.2.7 Oderwire Messages

4.3 Summary

45

46

47

50

51

52

53

54

55

5 SYSTEM DESIGN and IMPLEMENTATION

5.1 Introduction

5.2 Equipments Setup

5.2.1 HF Transceiver

5.2.2 HF Modem

5.2.3 Dipole Antenna

5.3 System Design

5.3.1 PACTOR Data Format

5.3.2 ALE protocols


5.3.2.2 Linking to another station

5.3.2.3 Sounding and Link Quality Analysis

(LQA)

5.3.2.4 Scanning

5.3.2.5 ALE Database

5.3.2.6 Comparison With Standard ALE

Systems

5.3.3 Graphical User Interface (GUI)

5.4 Summary

56

56

57

58

61

67

69

70

70

72

73

75

76

78

79

80

83

6 FIELD TESTING RESULT

6.1 Introduction

6.2 Equipments setup

6.3 Selection of Field-test Sites

85

86

87



x

6.3.1 Kota Bahru

6.3.2 Chemor

6.4 Channels Selection

6.5 Field-testing Timeslots

6.6 Results and Discussions

6.6.1 Skudai-Kota Bahru Reults

6.6.1.1 Sounding Results During Timeslot 1

6.6.1.2 Sounding Result During Timeslot 2


6.6.1.4 Comparisons Between Skudai-Kota

Bahru Results and ASAPS Prediction

Results

6.6.2 Skudai-Chemor Result

6.6.2.1 Skudai-Chemor Sounding Results

During Timeslot 1

6.6.2.2 Skudai-Chemor Sounding Results

during Timeslot 2

6.6.2.3 Comparisons Between Skudai-Kota

Bahru Results and ASAPS Prediction

Results

6.7 Summary

88

90

91

92

93

96

97

103

109

116

118

118

125

131

133

7 Conclusions and Recommendations

7.1 Conclusions

7.2 Recommendations for Future Works

135

136

REFERENCES 138

APPENDICES 143



xi

LIST OF TABLES

TABLE

NO.

TITLE PAGE

3.1 Station specification for Skudai-Kota Bahru circuit 31

3.2 Station specification for Skudai-Chemor frequency

prediction

34

4.1 ALE Operational Rules (listed in order of decreasing

precedence)

41

4.2 ALE word type and its functions 43

5.1 Preambles and their functions 71

5.2 Example results of LQA 77

5.3 Tables in ALE database. 79

5.4 Comparisons of ALE 80

5.5 Functions available on the system’s GUI 82

6.1 List of channels used in field-testing 92

6.2 Timeslots allocation 93

6.3 LQA Score categories 95

6.4 Skudai-Kota Bahru Result Analysis for Sounding made

by Skudai during timeslot 1

99


by Kota Bahru during timeslot 1

102

6.6 Summary of LQA results for Skudai-Kota Bahru Circuit

during timeslot 1

103



105



xii



108

6.9 Summary of LQA Result for Skudai-Kota Bahru Result

during Timeslot 2

109



111



114

6.12 Summary of LQA Result for Skudai-Kota Bahru Circuit

during Timeslot 3

115

6.13 Result analysis for Sounding made by Skudai during

timeslot 1

120

6.14 Result analysis for Sounding made by Chemor during

timeslot 1

123

6.15 Summary of LQA Results for Skudai-Chemor Circuit

during Timeslot 1

125

6.16 Result analysis for Sounding Made by Skudai during

Timeslot 2

127

6.17 Result analysis for Sounding made by Chemor during

timeslot 2

129

6.18 Summary of LQA results for Skudai-Chemor Circuit

during Timeslot 2

131



xiii

LIST OF FIGURES

FIGURES NO. TITLE PAGE

2.1 The ionosphere layers 9

2.2 HF propagations 13

2.3 Multipath in HF propagation 15

3.1 Vertically indices ionosonde 22

3.2 Upper and lower frequency range for HF sky wave

communication

28

3.3 GRAFEX frequency prediction table for Skudai-Kota

Bahru circuit

31

3.4 Field Strength Table for Skudai-Kota Bahru circuit 34

3.5 GRAFEX frequency prediction table for Skudai-

Chemor circuit

35

3.6 Field Strength Table for Skudai-Chemor Circuit 37

4.1 ALE state diagram 42

4.2 The general structure of an ALE word 43

4.3 ALE word coding and interleaving process 45

4.4 Frame Structure 46

4.5 Basic call structure 48

4.6 Multiple channel call protocol 49

4.7 Structure of a sound 52

5.1 Kenwood TS570D HF transceiver 57

5.2 Connection between transceiver to computer using

RS-232C cable

58

5.3 Kantronics KAM ’98 modem 59

5.4 Wiring to connect the modem and transceiver 60



xiv

5.5 Connection between HF modem and transceiver 60

5.6 System setup 61

5.7 Dipole antenna 62

5.8 Dipole Antenna Vertical Plane Radiation Pattern 63

5.9 Dipole antenna horizontal Plane Radiation Pattern 64

5.10 Yagi antenna horizontal radiation pattern 65

5.11 Contruction of dipole antenna 66

5.12 Dipole antenna at DSP Lab, UTM 68

5.13 System flowchart 66

5.14 Basic structure of ALE 70

5.15 General structure of an ALE frame 71

5.16 Flowchart for link establishment 72

5.17 Call, response and acknowledgment frames 73

5.18 Sounding frame 75

5.19 Sounding process 73

5.20 User interface for the system 79

6.1 Equipments setup for field-testing 86

6.2 Location of field testing sites with estimated antenna

radiation pattern

87

6.3 Equipments setup at Kota Bahru station 89

6.4 Antenna setup at Kota Bahru 89

6.5 Equipments setup in Chemor 90

6.6 Antenna setup at Chemor 91

6.7 LQA result for sounding by Skudai station during

timeslot 1

98

6.8 Channels Ranking for Sounding by Skudai During

timeslot 1

98

6.9 LQA result for sounding made by Kota Bahru during

timeslot 1

101

6.10 Channels ranking for sounding by Kota Bahru during

timeslot 1

101

6.11 LQA result for sounding made by Skudai station

during timeslot 2

104



xv

6.12 Channels Ranking for Sounding by Skudai during

Timeslot 2

105


timeslot 2

107


timeslot 2

107

6.15 LQA result for sounding made by Skudai station

during timeslot 3

110

6.16 Channels ranking for sounding by Skudai during

timeslot 3

111


timeslot 3

113


timeslot 3

113

6.19 Comparisons between highest-ranked channels and

OWF values for Skudai-Kota Bahru circuit: sounding

by Skudai

116


OWF values for Skudai-Kota Bahru circuit: sounding

by Kota Bahru

117

6.21 LQA result of sounding by Skudai during timeslot 1 119

6.22 Channel ranking for sounding by Skudai during

timeslot 1

120

6.23 LQA result of sounding by Chemor during Timeslot 1 122

6.24 Channel ranking for sounding by Chemor during

timeslot 1

123

6.25 LQA result of sounding by Skudai during timeslot 2 126

6.26 Channel ranking for sounding by Skudai during

timeslot 2

126

6.27 LQA result of sounding by Chemor during timeslot 2 128

6.28 Channel ranking for sounding by Chemor during

timeslot 2

129



xvi


OWF for Skudai-Chemor Circuit: sounding by

Skudai

132


OWF for Skudai-Chemor circuit: sounding by

Chemor

132



xvii

LIST OF SYMBOLS

I φ - Angle of incidence

c f - Critical frequency

k - Correction factor

N f - Plasma frequency

h - Height

mh - Height of a layer’s peak

R - Levels of solar activity

Ap - Geomagnetic effects

Kp - Geomagnetic effects

TCC - Calling cycle

TSC - Scanning call cycle

TLC - Leading call section

Ts - Total scan period

Td - Dwell time

Trw - Redundant word time

Ts - Total scan periodTwr - Wait-for-response time

L - Length of the antenna

F - Desired dipole antenna frequency



xviii

LIST OF ABBREVIATIONS

AFSK - Audio FSK

ALE - Automatic Link Establishment

ALF - Absorption limiting Frequency

AMD - Automatic Message Display

AMTOR - AMateur Teleprinting Over Radio

ASAPS - Advanced Stand-Alone Prediction System

ASCII - American Standard Code for Information Interchange

BER - Bit-Error Rate

BUF - Best Usable Frequency

CDMA - Code Division Multiple Access

CME’s - Coronal Mass Ejection

CRC - Cyclic Redundancy Check

CS - Control Signals

CSMA - Carrier Sense Multiple Access

CW - Morse Code

DBM - Data Block Mode

DCE - DataCircuit-terminating Equipment

DTE - Data Terminal Equipment

DTM - Data Text Message

EIRP - Effective Isotropic Radiated Power

EMUF - E-layer Maximum Usable Frequency

EPR - Estimated Power Required

EUV - Extreme Ultraviolet

FEC - Forward Error Correction



xix

FSK - Frequency Shift Keying

GTOR - Golay Teleprinting Over Radio

HF - High Frequency

ISI - Inter Symbol Interference

LAN - Local Area Network

LQA - Link Quality Analysis

LSB - Least Significant Bit

LSB - Lower Side Band

LUF - Lowest Usable Frequency

MCMC - Malaysian Communications and Multimedia

Commission

MSB - Most Significant Bits

MUF - Maximum Usable Frequency

OWF - Optimum working Frequency

PACTOR - Packet Teleprinting Over Radio

RTCE - Real-Time Channel-Evaluation

RTTY - Radio Teletypewriter

SINAD - Signal–plus-noise-plus-distortion to noise-plus-

distortion ratio

SMARTNET - Skywave Management for Automatic Robust

Transmission Network

SNR - Signal-to-Noise Ratio

SSB - Single Sideband

TDMA - Time Division Multiple Access

TNC - Digital Terminal Node Controller

UD MUF - Upper Deciles Maximum Usable Frequency

UT - Universal Time



xx

LIST OF APPENDICES

APPENDIX TITLE PAGE

A ASAPS Prediction Results 143

B Kenwood TS570D Transceiver Specifications 148

C Kantronics Kam ’98 Modem Specifications 150

D Experimental License For HF 153

E LQA Results For Skudai-Kota Bahru Field-Testing 156

F LQA Results For Skudai-Chemor Field-Testing 161



CHAPTER I

INTRODUCTION

1.1 Background

For decades, HF radio frequencies spectrum from 3 to 30 MHz has been used

as a medium for long distance communication. This is possible because these bands

of frequencies are reflected back to earth by free electrons in the ionosphere layer.

By using the proper frequency and set of equipments, a person can communicate

with another person as far away as on the other end of the earth via the HF layer.

Moreover, transmissions of digital data such as text, fax and images is also possible

by using HF modem, which converts digital data into analog form when transmitting,

and converts analog data to digital form when receiving.

Compared to satellite communication, the cost to set up and maintain a HF

communication system is much lower [Abdullah et. all, 2003]. Also, unlike the high

payment needed to use satellite communication services, the usage of HF does not

require payment to any service provider. HF communication however, suffers from

several propagation problems and effects from the variation of the ionosphere layer.

But today, with new technologies and many researches done, HF radio’s usage hasbeen expanded and propagation problems can be overcome. Adaptive and automatic



2

radio technology for example, permits modern radio systems to adjust automatically

to changing propagation condition [Hess, 2000].

The purpose of this research is to design a HF messaging system that has

automatic link establishment (ALE) capability. The messaging system allows digital

data to be exchanged via HF medium. ALE is an adaptive radio technology, which

make HF radio communication more reliable and less prone to propagation problems

by automatically selecting the best channel to use at any given time and place.

1.2 Objective

The objective of this research is to allow effective and reliable data

transmission over HF radio with ALE capability. The system is to be built with

minimum cost and equipments so that it can be made available to amateur radio

operator, telemetry and shipping. The main features of this research are as follows:

i) Design a HF messaging system

ii) Improve the reliability of data transmission of the messaging system

by including ALE capability to the messaging system.

iii) ALE is implemented as software.

iv) Commercial modems and radios are used as the building block of

the system.

v) Field testing is conducted to verify the system.



3

1.3 Problem Statement

Unlike telephone line and fiber optic, the HF environment is not noiseless as

interference does exist; transmitted signal is distorted and with high noise levels

[Goodman, 1992]. The effects of multipath fading and interference are significant in

HF communication. Moreover, its propagation environment is also constantly

changing due to the seasonal and diurnal variations in the ionosphere. Propagation

conditions vary by location, frequency, season, time of day, and can be affected by

unexpected ionospheric disturbance.

The main challenge in HF communication is to choose the most suitable

frequency to be used for communication. Conventionally, radio operators must

always listen to HF channels, to find available channel for communication. However,

in order to do this, the operators must be highly trained in operating a HF radio,

besides knowledgeable in HF radio propagation and channel predictions. Another

way is by using propagation prediction programs that predict the best channel based

on empirical data. Unfortunately, this is not the best way to determine the best

channel for communication. The frequency prediction method does not give real time

channel evaluation because all the data are obtained from calculation and forecasting.

Sometimes, the data acquired are not accurate. This is due to unpredictable

propagation factors such as sporadic E-layer propagations, interference from other

users on an otherwise usable channel [Johnson et al, 1997]. To solve this problem,

ALE is used. ALE performs real time channel evaluation, and helps select the most

suitable frequency to be used at different time of day.

Even though ALE can help improve the reliability of HF communication,

available ALE systems today are in a form of optional equipment for HF system. The

equipment is usually known as ALE controller and has its own modem for ALE

purposes. Thus users who want to experience the benefits of using ALE, has to buy

the expensive equipments and end up having two different modems, each for ALEand data transmission.



4

1.4 Scope of Study

Existing systems such as ALE controllers developed by Rockwell-Collins

Company [Rockwell-Collins, 2004] and Rhode-Schwarz Company [Rohde-Schwarz, 2004],

implement ALE as additional equipment, which controls an HF radio. However in

this research, ALE is implemented as software and part of a messaging system. Thus

in the system developed in this research, no additional equipment is needed for ALE.

The scope of this research are as follows:

i) This research does not involve building a HF radio and HF modem.

Existing radio and modem is used.

ii) The equipment compatible with the system are limited to

KENWOOD TS-570D HF Transceiver and Kantronics Kam 98 HF

modem. This is because other equipments require different

controlling methods and may not be suitable for the system

designed in this research.

iii) Unlike existing systems, this system will use the same modem for

both data transmission and ALE purposes.

1.5 Research Methodology

The following steps are taken to achieve the research objective:

i) To understand the basic concept and problems, literature and

technology review on HF communication was done. Review on ALE

technology and available HF messaging systems is also required for

comparison and reference.



5

ii) Attend DSP and digital communication courses to enhance basic

knowledge on the area of the research.

iii) The system design begun with building a messaging system using

Visual C++. This system connects two computers via HF radio as a

medium. The program is capable to control basic functions of both

transceiver and modem such as transmitting data and scanning

through channels (for transceiver).

iv) The next step is to design the ALE system, first for single channel

followed by multiple channels. Next sounding processes, together

with link quality analysis (LQA) are included to the system.

v) Before testing the system, frequency prediction was done. The

purpose of this is to choose the suitable channel to use for field-

testing. Advanced Stand-Alone Prediction System (ASAPS) is the

frequency prediction software chosen used for this purpose.

vi) The final step was field-testing that which was conducted at several

sites in Malaysia.

1.6 Thesis Outline

This report is divided into seven chapters. Chapter 1 is the introduction;

which includes objective, scope of study, and problem statement. Next, in chapter 2,

the literature review on HF radio, including its propagation characteristic and

problems. Other than that, recent developments in adaptive HF radio communication

systems are also presented. Then chapter 3 describes on frequency management and

prediction, an important tool in HF communication. Next, explanation on ALE ispresented in chapter 4. In this chapter, the concept and theory of ALE is described



6

including the frame structures and protocols used. Following after that is Chapter 5,

which concentrate in explaining system design and implementation. This chapter

explains in detail how the system is built, including equipments used, system

requirements and ALE protocols. Then the result of the system’s field-testing is

presented in chapter 6. Here, the LQA results are presented using graphs and then

discussions are done based on the results. Finally the last chapter, which is chapter 7,

is for conclusion and recommendations.



CHAPTER II

LITERATURE REVIEW

2.1 Introduction

The ionosphere layer plays an important role in HF communication as the

refraction of HF radio wave occurs in this layer. Thus, the condition of the

ionosphere layers and the ionization level directly effects HF propagation. But HF

propagation also faces other problems such as multipath fading, noise and

interference. With such problems, communications using HF radio is very

challenging but not impossible. Generations of researches proves that HF can be

improve and become a reliable medium for wireless communications. This chapter explains about HF radio communications, including its propagation characteristics,

new technologies in HF radio communications and available HF radio systems

available today.



8

2.2 The Ionosphere

The ionosphere is a region in the atmosphere that extends from about 60 km

to 500km above ground. Ionosphere contains many positively charged ions, and free

electrons, both produced by ionization. Ionization is a process where electrons are

stripped off from neutral atoms of gas molecules in the ionosphere layer to form

positively charged ions. Ionization is caused by the extreme ultraviolet (EUV)

radiation from the sun. The stripped off electrons which are light and free to move

are responsible for refracting HF radio waves. Generally, the greater the number of

electrons the higher the frequencies that can be used [Australian Space Weather

Agency, 2005]. There are four layers of ionized particles, different in altitudes and

the number of electrons, which are the D, E, F1, and F2 layers as shown in Figure

2.1. The approximate heights for the layers are as follows:

• D layer : 50 to 90 km

• E layer : 90 to 140 km

• F1 layer : 140 to 210 km

• F2 layer ; over 210 km

During daytime, all four layers are present with height approximately from 50

to 600 km above the earth [NTIA, 1998]. At night however, only the F2 layer is

present because the layers D, E and F1 layers become very much depleted of free

electrons and disappear almost completely. Thus, ionosphere boundary also moves

upward to about 100km. Sometimes, sporadic E is also present in the E layer during

both the day and night.



9

Figure 2.1 The ionosphere layers

Between the layers, only the E, F1, sporadic E (when present) and the F2layers can refract HF waves. The D layer [McNamara, 1991] absorbs or attenuates

HF waves instead of refracting it. The E layer is the lowest region that can refract

radio waves. This layer however is only present during the day with maximum

ionization during noon. At night, only a small residue level of ionization remains in

this region. Sometimes, there exists another region in the E layer, which is called the

sporadic E layer. This layer has irregular cloud-like layers of ionization but share

common characteristics as the normal E layer. The sporadic E layer often lasts for a

few hours and move about rapidly under the influenced of high altitude wind patterns

[NTIA, 1998]. Above E layer is the F1 layer, which is not considered an important

layer in reflecting HF waves. This is because generally, signals that penetrate the E

layer will penetrate through F1 layer as well and reflected by the F2 layer. Besides

that, F1 layer also absorbs the HF waves [NTIA, 1998]. The most important region for

HF radio communication is the F2 layer. The F2 region has the highest altitude

making it the most ionized region and is present 24 hours a day. Actually, during the

night, the F1 layer merges with the F2 layer, resulting in a single F layer. More over,



10

F2 layer usually refracts the highest frequencies in the HF range and its high altitude

allows the longest communication paths.

2.2.1 Variations of the Ionosphere

The ionosphere is not a stable medium that allows the use of one frequency

over the year, or even over 24 hours [Australian Space Weather Agency, 2005]. The

main variations of the ionosphere, which must be taken into account, are diurnal

variation, seasonal variation, solar cycle and finally the variations with latitude.

2.2.1.1 Diurnal Variations

Throughout the day, the critical frequencies vary due to the availability of the

solar radiation. The presence of the sun is the primary force for ionization to occur.

So generally, when there’s plenty sun radiation, ionization will occur more rapidly

producing more free electrons. Starting from dawn, electrons are productively

produced in the ionosphere, causing the frequencies to increase until reaching their

maximum at noon. After that, the frequencies begin to fall due to electron loss and at

night, the regions D, E and F1 disappear. For the F2 layer, the diurnal variation is

rather complicated because it survives during the night. So all communication during

the night is by the F2 region and absorption of radio waves is lower. Through the

night, frequencies gradually decrease reaching their minimum just before dawn.



11

2.2.1.2 Seasonal Variations

The ionosphere also varies throughout the year accordingly to the seasons.

This is because the solar zenith angle (angle measured at the earth's surface between

the sun and the zenith) has a seasonal as well as diurnal variation, and also because

of the neutral atmosphere from which the ionosphere is created. For the E region, the

frequencies are greater in the summer than in winter. For the F region, around the

solar minimum, the summer noon frequencies are generally greater than those in

winter, but during solar maximum, the condition changes. Winter frequencies are

higher than those in summer. This condition is called the seasonal anomaly. In

addition, frequencies around the equinoxes (March and September)are higher than

both in summer and winter [Australian Space Weather Agency, 2005].

2.2.1.3 Solar cycles

Solar cycles take the length of about 9 to 14 years [Australian Space Weather

Agency, 2005]. During this cycle, the sun goes through a periodic rise and fall in

activity which affects HF communications. At higher levels of solar activity (solar

maximum) there are a numerous number of sunspots together with plages. Plages or

also known as faculae [McNamara, 1991] are large, irregularly shaped bright areas that

usually surround sunspots. These plages increase extreme ultraviolet or EUV

radiation thus increasing ionization level of the earth’s atmosphere and the number of

electrons in the ionosphere layer. As a result, frequencies of all ionospheric layers

will be greater. On the contrary, lower frequencies are supported at lower levels of

solar activity (solar minimum).



12

2.2.1.4 Latitude Variations

Latitude variation is caused by variation with solar zenith angle. During the

day, with the increasing latitude, the sun zenith increases. In other words, the solar

radiation strikes earth’s surface more obliquely and the intensity is decreases. Thus,

the electron density production also decreases with increasing latitude causing the

highest usable frequency to also decrease. However, for F region, during daytime,

instead of at the equator, the frequencies peak at 15° to 20° north and south of the

equator. This is called the equatorial anomaly. During the night, frequencies reaches

minimum around 60° latitude and this situation is known as mid-latitude trough.

2.2.1.5 Sporadic E

Sporadic E usually has comparable electron density to the F region.

Sometimes a sporadic E layer is transparent, meaning that signal can pass through it

to the F region. However, it could sometimes obscure the F region totally that signals

do not reach the receiver [Australian Space Weather Agency, 2005]. This is known

as sporadic E blanketing. If the sporadic E is partially transparent, some of the

transmitted signal could pass through it and refracted to the receiver by the F layer

but some of it that does not pass through sporadic E layer are refracted back to earth.

This may lead to partial transmission of the signal or also known as fading.

2.3 HF Radio Propagation

The three basic HF propagation modes are ground wave, direct line-of-site

wave and sky wave [Goodman, 1992]. Figure 2.2 shows the types of HF propagation.Ground wave travels along the surface of the earth thus suitable for short-range



13

communications. Direct line-of-sight wave may interact with the earth-reflected

wave depending on terminal separation, frequency and polarization. Sky wave on the

other hand is refracted back to earth by the ionosphere, making beyond line of sight

communications possible. This discussion therefore concerns only with sky wave.

Figure 2.2 HF propagations

For sky wave propagation, transmitted radio wave travel a distance until it

reaches the ionosphere. The radiated waves are bent continuously in the ionosphere

and then returned back to earth hitting it at the receiver. The path from the

transmitter to receiver is called the ray path. In practice, there are always at least two

ray paths for sky wave propagation. The ray path may have single hop, or multiple

hops. Plus it can be refracted by any one of the layers of the ionosphere [McNamara,

1991]. Hopping is a situation where depending on frequency, time of day and

atmospheric conditions, signals is bounce from the earth and refracted by the

ionosphere several times before reaching the receiver [ NTIA, 1998]. Multiple hops is

common in HF propagation that enables beyond line of sight propagation and under

the right conditions can give global reach.



14

Not all HF waves are refracted back to earth by the ionosphere. Some of the

frequencies are lost because of the absorption by the D layer while some frequencies

penetrate the ionosphere. Thus, there are upper and lower frequency bounds between

two terminals that can be used as guidance when transmitting signals. Only signals

within these bounds are refracted back to earth. For the lower bound, the lowest

usable frequency (LUF), as statistically calculated is the lowest frequency which the

field intensity at the receiving antenna is sufficient to provide the signal-to-noise

ratio (SNR) on 90% of the undisturbed days of the month [ NTIA, 1998]. For the upper

bound, maximum usable frequency (MUF) indicates the maximum frequency that will

be refracted by the ionosphere for a certain circuit. Therefore signals greater than

MUF for a particular region will penetrate that region. For the F region, the MUF is

divided into three. The most important one is the lower deciles MUF (Optimum

working Frequency or OWF) which have 90% chance of being supported by the

ionosphere [Australian Space Weather Agency, 2005]. The others are the median and

upper deciles MUF which has 50% and 10% supported by the ionosphere,

respectively.

The usable frequency in HF communication can be predicted for a given

circuit. Frequency prediction is important in HF communication as it help operators

to choose the possibly good channels. With the help of computers, prediction method

today is much easier yet can provide results that are more advanced. These type of

software are available in the market today such as ASAPS [Australian Space

Weather Agency 2003], NTIA/ITS HF Propagation Model by the U.S. Department

of Commerce [U.S. Department of Commerce, 2005], and Propagation Resource

Manager (PropMan-2000) by Rockwell Collins Inc. [Rockwell-Collins 2005]. This

topic will be discussed further in Chapter III.



15

2.3.1 Multipath Effects on HF Propagation

Multipath fading results from dispersion of the signal as it travels through the

communication medium. It may be caused by factors such as multiple patches of

ionization within the same layer, by reflection from one or more distinct layers

(multimode), or by multiple ionospheric bounces from a specified layer or layers

[Goodman, 1992]. This causes the received signals to interfere with each other as

shown in Figure 2.3. Depending on the time difference between the reflected

components, multipath fading will lead to time selective fading and frequency

selective fading.

Time selective fading or flat fading [McNamara, 1991] is a phenomena where

dispersed signals arrived at the receiver in different phases. As a result attenuation or

cancellation will occur depending on how big the phase differences. Cancellation of

a signal will occur if the phase different is 180 degrees. In addition, Doppler shift and

spread due to relative movement of the ionosphere determine the fading rate and fade

duration.

Figure 2.3 Multipath in HF propagation



16

Frequency selective fading and time delay spread is caused by multihop or

reflection of signal on multiple layers. When there is significant time difference

between the reflected components, time delay spread causes inter symbol

interference (ISI) phenomena for digital communication, where adjacent symbol

interfere with each other. This problem limits the symbol rate to 100 baud per second

[Willink et al, 1996]. Frequency selective fading limits the possible subcarrier

frequencies usable as some frequencies are attenuated more compared to the others.

2.4 Automatic and Adaptive HF Communication System

The reliability of transmission in the HF band can be improved using

automatic and adaptive radio technology [Hess, 2000] [Blair et al, 2000] [Johnson,

2000]. These techniques reduce the burden on the operator by adding subsystems for

frequency management, link establishment, link maintenance, etc. Thus, automation

make the radio appears to communicate on the best channel, while simultaneously

performing many underlying functions [NTIA, 1998]. The definition of adaptivity is

the process associated with automatically altering operating parameters and/or

system configuration in response to changes in the time-varying channel propagation

conditions and external noise. The aspects of communication system which can be

optimized to achieve maximum data throughput are channel selection, modem bit

rate, data link frame size, modem interleaver setting and transmit power level.

Selection of the best available HF channel is the most powerful technique that

can be used to optimize throughput. Two important adaptive processes for this

purpose [Hess,2000] [Redding -Weddle, 1994] are Automatic Link Establishment

(ALE) and Link Quality Analysis (LQA). ALE is a robust [NTIA, 1998], adaptive

radio method for automatically establishing communications over HF single

sideband (SSB) links using the best channel possible. An ALE system automates the process a trained operator would normally perform to establish a link [Beamish,



17

1991] [Rohde-Schwarz, 2005]. LQA on the other hand is a method of assessing

channel quality, so that connections occur on the best frequency. This technique is

used when a station has a number of channels assigned to it. To improve the

reliability of ALE, typically, LQA is added into an ALE system.

2.5 Recent Developments in HF ALE Messaging System

In Europe, the HF Messenger™ [Soyer, 2001] created by Rockwell-Collins,

France is an advanced HF data communication software. It implements the NATO

STANAG 5066 standard and uses Q9600 modem device implementing the MIL-

STD-188-110B waveform and equipped with ALE capability. The main objective of

this system is to permit personal computers to exchange text, files, facsimiles, images

and pictures at data rates equivalent to current satellite radios over an HF medium.

This system also provides wireless transmission between several HF users for

broadcast, multicast or point-to-point with services in LAN operating environment.

The main application offered by this system is HF e-mail for ground, tactical

airborne and maritime.

Battle Force Email 66 [Renfree, 2001] is an improved version of HF

Messenger developed by the U.S Navy. This system operates in a Carrier Sense

Multiple Access (CSMA) network discipline and follows the STANAG 5066

protocols. To avoid collisions, this system applies point-to point connection between

two stations. Upon contact, two systems negotiate in a link setup in accordance with

STANAG 5066 protocols. After transferring emails traffic and other data, the links

are closed. During data transfer, all other stations stay silent.

Third-generation technology for HF radio networking [Johnson, 1998] wasdesigned to efficiently support large, data-intensive networks as well as the



18

traditional voice and smaller network applications of second-generation HF

networks. It supports separate calling and traffic channels, although calling channels

may be used for traffic when necessary. Third-generation ALE (3G-ALE) used in

this system to quickly establish one-to-one and one-to-many (both broadcast and

multicast) links. 2G-ALE is an asynchronous system, while 3G-ALE operates in

synchronous mode. Simulations and prototype measurements [Johnson, 2000]

indicate that the new generation of technology will support improvements in network

size and traffic throughput and to connectivity in challenging environments.

SMARTNET (Skywave Management for Automatic Robust Transmission

Network), an adaptive HF radio system has been developed by Rockwell

International Corporation’s Communication Systems Division [Redding -Weddle,

1994]. This system is a technology test bed for adaptive HF communications which

have many advance features of a fully automatic, computer-controlled HF network.

The system uses both time division multiple access (TDMA) and code division

multiple access (CDMA) channel access protocol to prevent contention. The system

selects optimum frequencies and produces a very low effective isotropic radiated

power (EIRP) using automatic power control to set the transmitter power. The

system adapts to changing propagation conditions by varying frequency, power and

data rate. The adaptation is done at each end of the link, adjusting all parameters

independently so that optimum connectivity is maintained. Tests have been done to

compare this system and an adaptive system based upon the FED-STD-1045A. The

purpose of this test is to determine whether the SMARTNET system operate in the

manner that it was designed to. Overall test results shows that the goal of this

experiment is achieved. SMARTNET automatically maintained the connection with

minimum power, selected an optimal transmit frequency, and provided link

availability 100 percent of the time. Compared to ALE results, this is a significant

improvement.

Existing commercial HF e-mail and messaging system [Sailmail, 2004]

[Cruiseemail, 2004] does not have adaptive radio capability. This capability is onlylimited for military messaging systems such as [Soyer, 2001] [HF email, 2004].



19

There exist however ALE controllers [Rockwell-Collins, 2004] [Rohde-Schwarz, 2004]

that controls a radio in order to determine the best channel to be used. These ALE

controllers has its own embedded modem for ALE purposes.

2.6 Summary

Chapter II presented the literature review for this research. It began with

introduction to the propagation medium, the ionosphere. The explanation includes

the layers in the ionosphere, and the variations in the medium. After that, the

overview of HF propagation is presented, focusing on the skywave. Problems in HF

propagation are also discussed. The problems are mainly caused by multipath and

resulted in attenuation of the received signals.

Chapter II also discussed on automatic and adaptive HF communication

system. As explained above, automatic and adaptive methods help to improve HF

communications by handling the changes in propagation medium. Finally, in this

chapter, some of the recent development in HF Messaging systems are discussed.

Some of these technology are already implemented and used, while some are still in

simulation phase.

With knowledge supported from the Chapter II, the next two chapters will

present in detail on HF propagation prediction and ALE.



20

CHAPTER III

FREQUENCY PREDICTION FOR HF COMMUNICATION

3.1 Introduction

As explained in Chapter II, HF is not a stable medium for wireless

communication. Therefore communicating via HF medium can sometimes be

challenging. At times, the optimum frequency is not used for communication. Thus,

frequency prediction programs help users to predict the best frequency to use at the

specific time and circuit before starting a communication session. Using prediction

software, the operator only needs to enter the required parameters and the predicted

best frequency and operating conditions are displayed almost immediately. The

results however, are predicted results based on calculation and not necessarilycorrect. But it can be used as guidance in selecting which frequencies to be used.

Thus in this chapter, the importance of frequency and performance prediction in HF

radio communication will be explained.



21

3.2 Types of Frequency Prediction

There are two types of ionospheric prediction methods, which are long-term

predictions and short-term prediction [Goodman-Reilly, 1998]. Long-term predictions

are done based on empirical data, which are results from previous studies. Often,

long-term prediction is based on a prediction of the solar activity level. On the other

hand, short-term prediction depends on real-time data. The short-term prediction can

either be forecasting or nowcasting. Forecasting is usually based on established

cause-and-effect relationship. Nowcast is based on results from real-time channel-

evaluation (RTCE) systems. But regardless the duration types, the steps to do

prediction are as follows [McNamara, 1991]:

i) Predict the sun’s activity during the time for which the

required predictions will apply.

ii) Set up an ionospheric model that represents the ionosphere

condition based on the predicted level of solar activity.

iii) For the ionospheric model, calculate the geometry and

propagation modes for the circuit under consideration.

iv) Calculate the MUF, LUF and field strength.

3.3 Ionospheric Measurement

Ionospheric condition is the key factor that affects HF propagation. Thus

before predictions of the HF propagation performance can be done, we must first

know how to measure the condition of the ionosphere. Among the ionospheric

measurements are the MUF of both F and E layers and also LUF. These

measurements are vital in frequency prediction as it helps determines the best

channels to use.



22

3.3.1 Ionograms

Ionograms are recorded tracings of reflected high frequency radio pulses

generated by ionosonde. Ionosonde as shown in Figure 3.1 is a method of measuring

the plasma frequency as a function of altitude. A train of pulses at increasing

frequency is transmitted vertically into the ionosphere [Johnson et al, 1997], every 15

minutes. This method is known as vertically incidence ionosonde. The time delay

between the transmission and reception of the pulses is recorded at the receiver’s end

and multiplied by the speed of light to determine the virtual height of the ionospheric

reflection. But once the ionosonde frequency exceeds the critical frequency of a

given layer, it penetrates that layer and does not return that signal. Then the results

are plotted in a graph of the reflection virtual height versus operating frequency.

Besides using vertically incidence ionosonde, ionograms can also be

generated using two other ionosonde methods. One method is where the transmitter

and receiver are separated by long distance, giving an oblique ionogram. But if

circuit length, i.e. the distance of ionosonde transmitter and receiver are not fixed, the

ionogram generated is called backscatter ionogram. In this method the signals are

scattered at the surface of the earth back along the original direction.

Figure 3.1 Vertically incidence ionosonde



23

3.3.2 MUF and LUF Calculations

MUF calculation depends on two things, which are the critical frequency,

c f of the ionosphere at the reflection point and the geometry of the circuit. MUF is

given by the formula

I c f MUF φcos= (3.1)

I c f MUF φsec= (3.2)

where I φ is the angle of incidence. The factor I φsec is called obliquity factor for

the circuit, because it relates [McNamara, 1991] the ionosphere at the reflection or

midpoint of the circuit. Obliquity factor varies with circuit length and is equal with

1.00 for a very short circuit. A correction factor k is multiplied to the obliquity factor

in order to take into account the facts that the earth and ionosphere are both curved.

The value of k is usually 1.1 under most conditions. The equation used to calculate

the MUF for reflection at a given altitude in the F layer is shown in equation (3.3).

This equation can be used provided the critical frequency c f is replaced with the

plasma frequency at the reflection height, N

f (h).

)(φsec)( h f h MUF I N •= (3.3)

where h is the height where we want the reflection to occur. The corrected obliquity

factor, k for an F2 propagation mode for a standard distance of 3000km, M(3000) F2

is derived routinely from ionograms and mapped in much the same way asc

f ,F2.

Besides absorption caused by the ionosphere, LUF also depends on things

such as signal to noise ratio and E-layer screening [Goodman, 1992]. Thus to calculate

the LUF, empirical data are used. For short circuits and well-planned equipment, it

can be related quite simply toc

f E by using a simple formula. This is due to the fact

that absorption is mostly due to the D region, which depends on the zenith angle in



24

much the same way as the c f E. For the long circuits the LUF can be set equal to the

first frequency, which is just too high to be propagated on second mode E-layer

propagation, since any signal reflected twice by the E layer will be severely

attenuated. At night however, because there is no absorption, the antennacharacteristics, the transmitter power, and the noise level, all of which vary with

frequency, control the LUF.

3.4 Important Factors in Frequency Prediction

Before predictions can be performed, several factors must first be considered.

Important factors in frequency prediction program are such as antenna specifications,

the expected signal-to-noise ratio, the ground or surface properties, and finally solar

and geomagnetic indices. These factors are important as they have direct effect on

the ionosphere. Not considering the factors listed in the subtopics below may lead to

unreliable and inaccurate predictions.

3.4.1 Ionospheric Models

Ionospheric model is the values of ionospheric condition and parameters for a

given circuit that is modeled from the predicted sun activity for a given circuit. But

most of the time, the parameters needed are critical frequencies [McNamara, 1991]

of the E and F layers,c

f E andc

f F2, and the height of the peak of the F layer, 2F hm

.

As for E layer, the value of E hm

is fixed at 110km. The maps of ionospheric

parameters are based on the median values observed at the 180 or so stations all over

the world for low and high levels of solar activity.



25

3.4.2 Geometry of The Circuit

The geometry of the circuit determines the obliquity factor and thus the MUF.

To calculate the geometry of the circuit, we must first determine the propagation

mode that we want to consider. In practice, we need to consider lower order modes.

Modes that involve more than two reflections in the E layer may be ignored as

reflections in this layer suffer much heavier absorption than those reflected in the F

layer. After the propagation modes have been decided, the obliquity factor for each

hop of the propagation modes and the values of c

f E,c

f F2and hmF2 at each reflection

point can be calculated.

3.4.3 Ionospheric Index

Sunspot number is the conventional index of the solar cycle that can be used

to predict ionospheric frequencies. However, using sunspot number alone is not

enough to predict the frequency [Australian Space Weather Agency, 2005]. This is

because the condition of the ionosphere is also affected by other factors such as

geomagnetic storms, the time of day, and the season. Thus for that reason, the usage

of sunspot number can be replaced with ionospheric index. The ionospheric index is

derived from observing the ionosphere over several solar cycles and plots the graphs

of maximum ionospheric frequency against the sunspot number [Australian Space

Weather Agency, 2005]. From the results, the relationship between frequency and

sunspot number is obtained. Then, using the recently observed maximum ionospheric

frequencies, the ionospheric index is derived using the relationship derived before.

The ionospheric index value is averaged over a group of stations, canceling out any

variations which occur at only individual stations, and leaving the variations which

are common to all stations [McNamara, 1991]. However, the value of ionospheric

index is slightly different from the real sunspot number. An example of an



26

ionospheric index is the T-index [Australian Space Weather Agency, 2005], the

ionospheric index used by the Australian Space Weather Agency.

3.4.4 Other Parameters

In order to do reliable predictions, propagation prediction programs use

several input parameters such as antenna specifications, the expected signal-to-noise

ratio, the ground or surface properties and in addition the best and correct solar and

geomagnetic indices. Most of the mentioned parameters are mandatory to establish

correct propagation estimation chart, graph or map. Although there is not one

program that uses all of the parameters, most reliable programs use a high variety of

them. The parameters are as follows [NTIA, 1998].

i) Propagation environment, which are the date, the season, the time of day,

required SNR and required reliability.

ii) Transmitter terminal: power, antenna type and gain, frequency, coupler

loss, SNR, band range, antenna height versus wavelength.

iii) Receiver terminal: signal sensitivity, bandwidth, man-made and

atmospheric noise, antenna type and gain, band range, antenna height

versus wavelength.

iv) Ground: conductivity and dielectric constant.

v) Communication path: crossing land and/or sea surfaces, gray or auroral

zones, the equatorial belt, south Atlantic and south Asiatic anomaly areas.

vi) Solar effects: smoothed sunspot number or solar flux, solar flares and

coronal mass ejection (CME’s).

vii) Geomagnetic effects: Ap and Kp indices, magnetic inclination, and gyro

frequencies.



27

3.5 Advanced Stand-Alone Prediction System (ASAPS)

ASAPS is a propagation prediction program created by the Ionospheric

Prediction Service (IPS), Radio and Space Services of the Australian Department of

Industry, Tourism and Resources [Australian Space Weather Agency, 2003]. The

typical use of ASAPS is to estimate the expected SNR for several specified

frequencies of operation. Among the inputs for ASAPS are the location of

transmitting and receiving stations, the type of antenna used, the time and date of the

prediction, the transmitter power, and the T-index. Then based on the inputs entered

by the user, ASAPS will calculate the propagation and then generates the following

outputs

i) HF path distance and great circle path bearings from site to site

ii) Best usable frequency (BUF) for each hour and the corresponding ray

path elevation angle

iii) Signal power, total noise power, SNR

iv) Probability that each of the likely propagation modes is present provided

for each hour of the day at each of the nominated frequencies.

3.5.1 ASAPS GRAFEX Frequency Prediction

The predictions in ASAPS are implemented using GRAFEX frequency

predictions. GRAFEX predictions provide HF propagation information concerning

transmission conditions of the first two propagation modes via the E and F layers for

a given HF radio circuit. For each hour of the day, the program predicted the range of

HF sky wave communications which are the Upper Deciles MUF (UD MUF), the

median MUF, Optimum working Frequency (OWF), median E-layer MUF (EMUF),

Absorption limiting Frequency (ALF) and the elevation angles for each mode.



28

ALF indicates the lowest usable frequency. Frequencies below and near ALF is

most likely to be highly attenuated [Australian Space Weather Agency, 2005], thus

must be avoided. During day time, frequencies lower than ALF are absorbed by the

D region. However, during night time ALF becomes zero because D region does not

exist. OWF frequency on the other hand has 90% chances of success during the

period of prediction. Frequency that should be used is between the ALF and OWF as

these frequencies also have 90% chances to succeed. The MUF frequency on the

other hand has 50% of success. Therefore, communicating using frequencies

between OWF and MUF has from 50% to 90% chances of success. The chances

increase when the frequency used is nearer to OWF. The highest usable frequency,

the upper deciles MUF only have 10% of success. Frequencies between upper deciles

and MUF have only 10% to 50% of success, thus should be avoided. Figure 3.2

shows the range for HF sky wave communication.

Figure 3.2 Upper and lower frequency range for HF sky wave communication.

The predicted results are represented graphically using GRAFEX tables and

graph. The tables and graphs are as below

a) GRAFEX Table

This table gives an overall picture of the probability of HF

communications for the given circuit. Frequencies performance prediction

at each hour throughout a day for both first and second mode is shown.

The performance of each channels are represented using symbols, with

UD (10% success)

MUF (50% success)

OWF (90% success)

ALF (zero at night)

<10% success

10-50% success

50-90% success

>90% success



29

each symbol representing the probability of successful communication at

a particular hour. The elevation angles for the different modes are also

predicted.

b) GRAFEX Graph

This graph shows results from GRAFEX table, represented in graphical

form. It consists of a plot of the MUF, OWF, EMUF and ALF for each

mode of propagation. Different colours are used to differentiate the

frequencies.

c) GRAFEX Frequency Plan Table

In this table, the recommended frequency to be used at every hour is

presented. The frequencies are based on the preselected set of frequencies

entered by user. For each propagation mode, predicted frequencies are

divided into two parts based on levels of probability of ionospheric

support, which are greater than 90%, and between 50 to 90%. Then for

each hour, the recommended frequencies are shown.

d) GRAFEX Frequency Plan Graph

This is the graphical representation of frequency plan table. For each

propagation mode and for each hour, the frequencies are plotted against

takeoff angle to give a visual representation of the width of the takeoff

angle range and the relative positions of these ranges for the various

modes.

e) GRAFEX Frequency Table

This table shows the predicted UDMUF, MUF, OWF, EMUF and ALF

for each hour and the first two propagation modes.



30

3.5.2 ASAPS Field Strength Prediction

Other than GRAFEX frequency prediction, field strength prediction is also

used in selecting the best frequency. The prediction only predicts the best frequencies

that should be used, based on the frequencies entered by the user. The outputs of this

prediction are: all noise value (median atmospheric + galactic + man-made), noise

pathloss, field strength, signal to noise ratio, best usable frequency (BUF), virtual

reflection height and estimated power required (EPR). The results are then

represented using table and graph below.

a) Field Strength Table

This table shows all output of the field strength prediction as mentioned

above, for a particular mode for each circuit. The results are shown for each

hour. The table is used as a reference when selecting which channel to use.

b) BUF Graph

The results are represented by two graphs. The first one is the BUF graph,

which shows the best usable frequency for each hour of a day. Then the

second graph shows the signal-to-noise (SNR) in dB and noise field strength

levels in dBV/m.

3.5.3 Frequency Prediction for UTM Skudai-Kota Bahru Circuit

Kota Bahru in Kelantan is a station for field testing of this research. It is

situated 535 km from Skudai and therefore HF communication to Kota Bahru is via

sky wave. The prediction is done for the month of March 2005. The specifications on

this circuit are shown in Table 3.1.



31

Table 3.1 Station specification for Skudai-Kota Bahru circuit

Station Latitude Longitude Antenna

Skudai 1 33.6 103 39.0 7 MHz half-wavelength dipole antenna

Kota

Bahru

6 10.2 102 16 7 MHz half-wavelength dipole antenna

Both stations use the same set of frequencies, which are: 3.853 MHz, 3.959

MHz. 6.65 MHz, 6.702 MHz, 7.08 MHz, 7.10 MHz, 7.686 MHz, 8.002 MHz, 8.113

MHz, 8.19 MHz, 8.71 MHz, 9.108 MHz, 9.146 MHz, 10.1 MHz, 10.9 MHz, 14.365

MHz, and 14.773 MHz. The results from the prediction are shown below in Figure

3.3 which is the GRAFEX frequency prediction table.

Figure 3.3 GRAFEX frequency prediction table for Skudai-Kota Bahru circuit



32

Figure 3.3 shows the result in a form of GRAFEX table. This table shows the

performance of each frequency during the month of March 2005. The results are

represented in the form of symbols. Each symbol represents the propagation

condition at each hour. From the GRAFEX table in Figure 3.3, the first row shows

the name of the circuit, the distance and the period of prediction. The next row shows

the name of transmitter station (the station where prediction is done) and its position,

based on latitude and longitude. Then the bearing of the circuit is shown. Next to it,

the value of T-index of the moth of March 2005 is shown. On the third row, the name

and position of the receiver station is shown. Finally the type of circuit path is

shown. In this case the type is short path. Moving on to the fourth row, it can be seen

that the left part is labeled as “First Mode” and on the right part “Second Mode”.

This means that columns on the left side represent values of first mode propagation

prediction and columns on the right represents second mode propagation predictions.

Then on the next row, on the left hand side, the suitable elevation angles for both

first mode F and first mode E layer are shown. The same goes on the right hand side

where the elevation angles for second mode F and E layer are shown. The rest of the

rows represent the predicted frequencies for every hour of a day in the month of

March 2005.

On the left hand side, the first column (UT) represents the universal time.

Thus for local time, the time is UT+8. The next column is the OWF, followed by

EMUF and ALF for first mode propagation for F layer. Then the columns in the

center which are labeled with “Frequency” represent the range of frequencies from 1

to 40 MHz. The performance of each frequency is labeled with symbols. The

meaning of each symbol is explained at the bottom of Figure 3.3. Then on the right

hand side columns, the value of OWF, EMUF and ALF for second mode are also

shown. If a user wishes to communicate at 0800-hour local time (00 UT), by

referring to Figure 3.3, the results are as follows

i) The OWF frequency is 6.7 MHz, the EMUF frequency is 4.8 MHz and the

ALF frequency is 2.6 MHz.



33

ii) Frequencies 2.6 MHz and below should be avoided as this is the ALF or

absorption limiting frequency.

iii) Frequencies above 10 MHz should also be avoided because communication

within these frequencies only have 10% chances to succeed throughout the

month.

iv) The best frequency to use is between 3 to 6.7 MHZ (the OWF frequency for

first mode). However, these frequencies are labeled with symbol “M”, which

means that both first and second F modes are possible for those frequencies.

To decide which channel to use, a user must then refer to the field strength

table as shown in Figure 3.4. It is another useful reference when planning

communication. This table shows the Signal to noise ratio or SNR for OWF, MUF

and also SNR value for a set of frequencies selected by the user. In this case, the

frequencies stated earlier in this subsection are used. Other than showing circuit

information such as the name and position of stations, distance and T-index, this

table also shows the type of antenna used at both station. This information is shown

on the right hand side on row 3 and 4. in this case, the antenna used is a horizontal

dipole antenna. Other than that, the type of noise and the transmitted power is also

shown. Based on the results, users should use frequencies with high SNR values to

ensure good communication link. For example, at time 0800-hour local time, user

should avoid using frequencies from 3.9 to 4.00 MHz, as these frequencies have very

low SNR value. The rest of frequency prediction results, such as GRAFEX

Prediction Graph and Frequency Plan Table are shown in Appendix A



34

Figure 3.4 Field Strength Table for Skudai-Kota Bahru circuit

3.5.4 FrequencyPrediction for UTM Skudai-Chemor Circuit

Chemor, a small town in Perak is another site for field testing of this research.

It is situated 452 Km from Skudai, thus the stations will be communicating using sky

wave propagation. The details of the prediction are as listed in Table 3.2 below. The

prediction is done in the month of June 2005 between UTM Skudai and Chemor,

Perak.



35

Table 3.2 Station specification for Skudai-Chemor frequency prediction

Station Latitude Longitude Antenna

Skudai 1 33.6 103 39.0 7 MHz half-wavelength dipole antenna

Chemor 4 43.8 101 6.0 7 MHz half-wavelength dipole antenna

As with Skudai-Kota Bahru circuit, both stations in this circuit use the same

set of frequencies, which are: 3.853 MHz, 3.959 MHz. 6.65 MHz, 6.702 MHz, 7.08

MHz, 7.10 MHz, 7.686 MHz, 8.002 MHz, 8.113 MHz, 8.19 MHz, 8.71 MHz, 9.108

MHz, 9.146 MHz, 10.1 MHz, 10.9 MHz, 14.365 MHz, and 14.773 MHz. The results

of the prediction are shown in the GRAFEX frequency prediction table in Figure 3.5.

Figure 3.5 GRAFEX frequency prediction table for Skudai-Chemor circuit



36

By referring to Figure 3.5, we can see that for this circuit, both 2E and 2F does

not exist. This means that the signals propagate using first mode only. To determine

the best channel to be used for a certain time, a user should follow the same steps as

discussed earlier for Skudai-Kota Bahru circuit. Again, 0800-hour local time (00 UT)

is chosen. Thus the results are as follows

i) The OWF frequency is 6.0 MHz, the EMUF frequency is 4.5 MHz and

the ALF frequency is 2.5 MHz.

ii) Frequencies 3 MHz and below are labeled with symbol “A”. These

frequencies should be avoided as they are highly absorbed.

iii) Frequencies above 8 MHz should also be avoided because

communication within these frequencies only have 10% chances to

succeed throughout the month.

iv) 4.0 MHz is labeled with symbol “B”, which means that both E and F

modes are available.

v) 5.0 MHz is labeled with symbol “F” which means that only first F mode

is available. Therefore, the best frequency to be used is between 4.0 to 6.0

MHZ (the OWF frequency for first mode).

vi) The next best frequencies to be used are from above 6.0 MHz until 7

MHz. These frequencies are labeled with symbol “%”, meaning that they

are usable from 50% to 90% of days in this month.

To decide which frequencies should be used, a user must refer to Field

Strength table for this circuit shown in Figure 3.6., where the SNR value for the

OWF, MUF and selected frequencies are shown. By referring to the 00 UT,

frequencies from 6.7 MHz until 8.2 MHz are usable because the SNR value is high.

Figure A.4 until Figure A.6 in Appendix A shows the rest of the ASAPS frequency

prediction results.



37

Figure 3.6 Field Strength Table for Skudai-Chemor circuit

3.6 Summary

This chapter explained HF performance prediction in details. Performance

prediction is important in planning HF communication because it helps the user to

choose the best channels to use. This will help to increase the chances of success in

communication via the ionospheric layer. The sun’s activity is the main factor that

affects the ionospheric condition. Thus, to predict the best frequencies, theionospheric index, which is similar to sunspot number, must be determined first.



38

Then the ionospheric model is set up to determine the MUF, OWF, and the ALF for

the desired time for the specific circuit. ASAPS is the prediction software used in this

research. The frequencies obtained from the ASAPS prediction are then used in

ALE. Prediction helps ALE to avoid using bad and unusable channels. Besides,

comparisons can be made between the results from ASAPS prediction and ALE.



CHAPTER IV

AUTOMATIC LINK ESTABLISHMENT (ALE)

4.1 Introduction

The manual processes to establish link with another station are as follows:

first, the operator must determine the best frequency to use by either listening to each

channel or using prediction programs. Then he must try to call the other station using

voice technique asking for permission to communicate. After the recipient station

replies and the calling stations operator acknowledge it, a link is therefore established

between the two stations and data can be exchanged. [Wan Roz, 2004]

Automatic Link Establishment (ALE) follows this same rule except that the

system automatically does the processes of determining the best channel to use and

linking to another station. The operator only needs to enter the receiver stations’

address and the system will consult its memory, select the best available assigned

frequency and then link to the other station. In other words ALE radio systems

simplify the complex usage of a radio system to become as simple as using a

telephone and reduces the need for skilled operators to operate a HF radio system.



40

ALE solves channel selection problems by continuously evaluating and

testing the channel reliability using its’ sounding and link quality analysis protocols.

An ALE system, at fixed time intervals will perform channel evaluation on each

channels assigned to the particular stations. The results are then saved so that it can

be used each time the station wants to communicate to another station. This chapter

explains about the ALE based on U.S Federal Standard 1045A [NCS, 1993]. The

purpose of this standard is to specify the basic procedures and protocols for

automated HF radio features such as frequency scanning, selective calling, ALE, link

quality analysis (LQA) and sounding. This standard is used worldwide as the most

reliable reference as it provides complete details on waveform, coding, and protocols

to support ALE.

4.2 ALE Protocols and Operational Rules

ALE, based on the Federal Standard 1045A has its’ own set of operational

protocols for both system operating using single and multiple channels operating in

the data link layer of HF communications layer as shown in Appendix A. An ALE

system incorporates the basic operational rules listed in Table 4.1. However, some of

these rules may not be applicable uncertain applications [Johnson et al, 1997].

“Always listening” (Rule 2) for example is not required during temporary periods

when not technically possible, such as during transmit with a transceiver, or when

using separate transmitter and receiver with a common antenna.



41

Table 4.1: ALE Operational Rules (listed in order of decreasing precedence)

Rule No. Rule Description

1 Independent ALE receiving capability in parallel with any other

2 Always listening for ALE signals (critical)

3 Always will respond (unless deliberately inhibited)

4 Always scanning (if not otherwise in use)

5 Will not interfere with active ALE channel (unless forced by operator

6 Always will exchange LQA with other stations when requested (unless

inhibited), and always measure the signal quality of others

7 Will respond in the appropriate time slot to calls requiring slotted

responses

8 Always seek (unless inhibited) and maintain track of their

connectivities with others

9 Linking ALE stations employ highest mutual level of capability

10 Minimize transmitting and receiving time on channel

11 Automatically minimize power used (if capable)

There are three states for an ALE system to be. The three states are available

states when a station is not link to another station, linking states where a station is in

the process of trying to connect with another station. If linking process fail, a station

shall return to available state. However, if the process is successful, the station will

enter the third state: the link state. A station enters this state when it has successfully

link to another station. In this state a wait-for-activity timer will be running. Figure

4.1 shows these three states.



42

Figure 4.1 ALE state diagram

The ALE procedures and protocols can be described into the following functions:

i) Calling

ii) Scanning

iii) Sounding

iv) Link Quality analysis (LQA)

v) Automatic Channel selection

vi) Order wire Messages

4.2.1 ALE Signal Structure

The basic part that builds up an ALE system is its signal structures. This

includes bit and word format and structure, coding, forward error correction, framing

and synchronization. This section will explain ALE signal structure and addressing

method.

Available

Linkin Linked

Send or receiveALE call

Linking fail

Linking succeed

Terminate link



43

4.2.1.1 Word Structure

Every ALE frame is composed of ALE words. An ALE word consist 24 bits

of information, designated W1 for most significant bits (MSB) through W24, which is

the least significant bit (LSB). An ALE standard word is divided into four parts; as

shown in Figure 4.2. The three first bits (also known as bits P1 through P3) represent

the preamble, which is very important to an ALE word as it determine the function of

an ALE word.. Then the following 21 bits are divided equally to build up a data field

that contains three characters. These three characters specify an individual address

character or ALE text, depending on the preamble.

Figure 4.2 The general structure of an ALE word

As mentioned above, preamble bits are responsible for determining the type

of an ALE word. There are eight word types, which are TO, THIS IS, THIS WAS,

DATA, REPEAT, CMD, THRU and finally FROM. All these words have their own

functions in an ALE frame as described in Table 4.2.

PREAMBLEP1- P3

CHARACTER 1(LEADING)C17 – C11

CHARACTER 2(MIDDLE)C27 – C21

CHARACTER 3(TRAILING)C37 – C31

W1 W3W4 W10 W11 W17 W18 W24



44

Table 4.2 ALE word type and its functions

Word Type Function

TO

(P3 P2 P1= 010)

Used as a routing designator to identify the address of the

destination station for whom the frame is intended.

THIS IS

(P3 P2 P1= 101)

Routing designator that identifies the address of the

station that is transmitting the frame

Indicates that the transmitting station is willing to

communicate with other stations

Also use in sounding frame

THIS WAS

(P3 P2 P1= 011)

Used exactly like a THIS IS word except that it indicates

that the transmitting station discourage or does not invite

communication from other stations.

DATA

(P3 P2 P1= 000)

Used to extend the data field of any previous ALE word

(except DATA itself)

DATA words are used to extend the additional characters

from three to six, sine or more, up to a total of 15

characters

Must be used alternately with REPEAT word.

REPEAT

(P3 P2 P1= 111)

Used with DATA word to extend an ALE word data field

When it follows a TO word, it performs as an address

expansion, allowing the transmitter station to send frame

to more than one receiver

THRU

(P3 P2 P1= 001)

Used in the scanning call section of the calling cycle only

with group call protocol.

CMD

(P3 P2 P1= 110)

A special order wire designator that is used within the

message section of an ALE frame.

FROM

(P3 P2 P1= 100)

An optional designator that can be used to identify the

address of the transmitting station early in the ALE

frame. It is used immediately after a CMD word.



45

4.2.1.2 Coding

To enhance the reliability of ALE words on the noisy HF channel, each one is

extended using 24-bit Golay forward error correction (FEC) code [Rohde-Schwarz,

2004]. The 24-bit ALE word is split into two, with each part containing 12 bits. Then

each part is encoded using the (24, 12, 3) Golay code and interleaved bit by bit

[Johnson et al, 1997]. This caused the bits number to double from 24 to 48 bits. A

stuff bit is added (always a 0) and the total bits in an ALE word now become 49.

Finally, the 49-bit block is repeated three times for a total of 147 bits to be

transmitted. The purpose of interleaving and redundant words is to spread the burst

errors so that errors on the actual data can be minimized. Because FED-STD 1045 is

intended for designing an ALE modems, the 147 ALE bits are then 8-ary FSK

modulated and transmitted. The entire ALE word including error correction consists

of 49 bits and is 392 ms long. Figure 4.3 shows the word coding and interleaving

process.

Figure 4.3 ALE word coding and interleaving process

PREAMBLE3 bits

CHARACTER 17 bits

CHARACTER 27 bits

CHARACTER 37 bits

12 bitsdata

12 bitsGola FEC

12 bitsdata

12 bitsGola FEC

------------------------------------- 0

Stuffing

bit

24-bits

ALE word

24-bits ALE word

with 24-bits Golay

FEC

49-bits ALE word

interleaved

Bit 0



46

At the receiver’s end, ignoring the 49th bits, the 48 bits are deinterleaved [Lay,

1996] and Golay (24, 12, 3) decoded where up to three errors can be corrected per

word. The receiver then performs the majority voting among the three copies of

received copies of ALE words.


The general structure of an ALE frame consists of destination address, an

optional message section, and a frame conclusion, which contains the address of the

station sending the frame. Figure 4.4 shows the general structure of a frame.

Figure 4.4 Frame Structure

a) Calling cycle

Calling cycle (TCC) is the initial section of all calls (except sounding) and is

divided into two parts: a scanning call cycle (TSC), and a leading call section

(TLC). Scanning call shall only be composed of TO words representing the

first word of the called station for individual calls. While leading call section

can be composed of TO words (and possibly DATA and REPEAT words),

containing the whole address for the called station.

b) Message

This optional section of all calls (except sounding) shall be composed of

CMD (and possibly REPEAT and DATA) words. This section is used insending order wire messages.

CALLING CYCLE(DESTINATION ADDRESS)

MESSAGE(OPTIONAL)

CONCLUSION(SENDER’S ADDRESS)



47

c) Conclusion

The third section of a call frame is composed of either THIS is or THIS WAS

(but never both) (and possibly DATA and REPEAT) words. Conclusions

must contain the whole address of the calling station.

d) Sound frame

A sound frame is an exceptional frame, where it does not have calling cycle

and message sections. A sound frame therefore only contain a conclusion

section and can possibly be made up of either THIS IS word or THIS WAS

(and possibly DATA and REPEAT) words.

4.2.2 Calling Protocol

An ALE system has its own protocol suite to handle linking process. This

protocol consists of three parts: an individual calling, a response and an

acknowledgment. A station is “always scanning” when not connected to other

station, listening for incoming calls. To establish a link, a calling station, say station

A calls destination station, say station B by transmitting a calling cycle containing

station B’s address (“TO B”), followed by a conclusion containing station A’s

address (“THIS IS A”). The calling station will try to link on the best channel

according to its LQA table. However, if it link cannot be established using that

channel, then the station will try linking on the next best channel. This procedure

shall continue until all the channels have been tried and no contact has been

successful. If this happened, the system will automatically return to available state,

continue scanning and alert the operator that the system failed to establish link.



48

The call structure is an essential element of the ALE calling protocol, which

is shown on figure 4.5. The calling cycle must consist of a scan call (Tsc) plus a

leading call (Tlc). Tsc must exceed the total scan period (Ts) of the called station in

order to capture the scanning receiver. Ts equals to probable maximum pause (Td) to

read words on each channel. Thusd s

T C T ×= . Tsc shall also be composed of

multiple address first words ( )∑ = 11 caT T which are multiple of the redundant word

time, Trw. That is:

scascT T nT nT ≥×=×= ∑ 11

(4.1)

The leading call (TLC) contains the whole called station address repeated only

twice( )∑=ac

T T 22 . Therefore the calling cycle is:

( )sacalcsccc

T T T T nT T T ∑∑ +≥+×=+= 22)( 1(4.2)

After sending the call frame, station A then shall wait for station B’s response in

a limited wait-for-response time (Twr). However, if station A does not receive

response from station B within wait time Twr, the call is considered unsuccessful; and

station A may try again or terminates the call.

Figure 4.5. Basic call structure

TO

B

THIS IS

A

THIS IS

A

THIS IS

A

TO

B

TO

B

TO

B

TO

B

TO

B

TO

B

TO

B

TO

B

SCANNING CALL(FIRST 3

CHARACTERS)

LEADING CALL

(WHOLE ADDRESS WORDS)

CONCLUSION

(TERMINATION)

CALLING CYCLE

REDUNDANT CALL

SCANNING REDUNDANT CALL

Note: “B” and “A” are graphic substitution for the actual three character for a basic ALE

address field.



49

Station B is also always scanning. If it detected an appropriately addressed ALE

call (“TO B”), the station shall stop scanning immediately and read the rest of the

signal. If the receive signal is correct, B shall send back response frame to A.

Immediately after sending the response, B shall wait for A’s acknowledgment and

data traffic, in it’s own preset time Twr. If A’s acknowledgment arrived later than Twr,

B treats it as a new individual call and provide a new response for it. If station B did

not receive any acknowledgment at all from station A, it terminates the link and

continue scanning. Upon receiving the response, A shall send the acknowledgment,

enter the linked state and alert the operator. The same goes at station B’s end, where

upon receipt of the acknowledgment, shall also enter the linked state and alert its

operator. Both stations can now send data traffic to each other. Figure 4.6 below

illustrates the calling protocol.

Both stations shall stay in linked state until one of them terminates the link. If

there is no data traffic being passed between the two stations within a preset time

wait for activity time limit (Twa), the station shall automatically terminates the linked

state and return to available state. To terminate a link, a station must send “THIS

WAS” word containing its own address to the other station. Upon receiving this, the

other station shall end the handshake, terminates the link and return to available state.

TO THIS IS

TO THIS IS

TO THIS IS

INDIVIDUAL CALL

RESPONSE

ACKNOWLEDGMENT

TCC A- TWR

B- TWR

TSC TLC

NOTE:

• Tcc = Tsc+ TLC

• Tsc – use first word(s) only

• TLC– use whole address(es) only

Figure 4.6 Multiple channel call protocol



50

4.2.3 Scanning

All ALE stations, when not committed to another station, continually scan a

preselected set of channels, or “scan set” stored in ALE memory, listening for calls

and ready to respond. Scanning process can be performed in scan rate of either two

or five channels per second. The minimum dwell time (Td min) on each channel is

the reciprocal of the scan rate, and the channels are scanned repeatedly in the same

order for the same period. This period, known as minimum scan period (Ts min) is

equal to the product of the number of channels (C) times the minimum dwell time

(Td min); that is,

T s min = C x T d min (4.3)

The radio will automatically stop scanning and wait at the most recent

channel if any of this following events occurred:

• Automatic controller input of stop scan (the normal mode of

operation)

• Manual input of the scan

• Activation of push to talk (PTT) line

• Activation of external stop scan line

By continuously scanning its assigned frequencies, an ALE station

maximizes the probability that an incoming call will be received. This channel

scanning behavior is one of the key automated techniques that enable reliable

communication over HF without the presence of skilled operator [Johnson et al, 1997].



51

4.2.4 Sounding

Sounding is part of ALE protocol where at a predetermined time interval; a

station automatically broadcast a very brief, beacon-like short message on each of its

unoccupied prearranged channels. This beacon-like message is then utilized by other

stations to evaluate connectivity propagation and availability of the sounding station.

The information is saved for later used as a reference for selecting known working

channel when trying to establish a call the sounding station.

To implement sounding, a timer is added to an ALE station so that the station

shall perform sounding on clear channels periodically. The sounding capability

maybe selectively activated by and the time interval can be adjustable by the operator

or controller according to the system requirements. Sounding signal is a unilateral

one-way transmission; meaning that no response is required from the station or

stations that receive sounding frames. Therefore, when the other stations “hear” the

sounding signal, they shall automatically display the addresses of all stations heard

momentarily, perform LQA calculation and then stored the data in LQA memories

for future linking use.

As it is only necessary to send the sounding stations’ identity, the sounding

structure only consists of conclusion (terminator), redundantly repeated. The whole

address of the sounding station is sent at least twice to ensure reception by scanning

receiver. Figure 4.7 shows the structure of the sound, which consists of either “THIS

IS” or “THIS WAS” words. Using “THIS IS” words indicates that potential callers

are encouraged. On the other hand by using “THIS WAS” words to build up a

sounding frame indicates that the sounding station discourage potential callers, i.e. it

does not want to communicate with other stations during that time. The total duration

of sounding must be compatible with the scanning time of the receivers so that it can

be encountered.



52

Figure 4.7 Structure of a sound.

4.2.5 Link Quality Analysis (LQA)

LQA is a process that measures the quality of the channels by placing a score

for each of them which incorporates three types of link analysis information: bit error

ratio (BER), signal–plus-noise-plus-distortion to noise-plus-distortion ratio (SINAD),

and optionally, a measure of multipath [NTIA, 1998]. These results are kept in a

table for future reference and it can be exchanged between stations by inserting the

values in LQA CMD word. More over, the tests are performed periodically to keep

the data current. LQA is added to an ALE system so that linking between stations

can be done using the best channel possible.

4.2.5.1 Bit Error Ratio (BER)

An ALE system performs a pass/fail LQA test on every received signal using

its critical examination on proper coding, structure and format. As an addition

assessment of link quality, basic BER measurement is performed. The measurementis obtained by counting the number of nonunanimous vote (out of 48) in the majority

THISWAS

A

THISWAS

A

THISWAS

A

THISWAS

A

THISWAS

A

THISWAS

A

THISWAS

A

THISWAS

A

THISWAS

A

SCANNING SOUND(WHOLE ADDRESS

WORDS)

REDUNDANT SOUND (WHOLEADDRESS WORDS)

SCANNING REDUNDANT SOUND,SOUND CYCLE



53

decoder. The BER score ranges from 0 to 48 with 0 (no two-thirds vote) being the

best score and 48 (no unanimous word) as the worst. It is performed on each

redundant triplet (3 Tw) word received and properly decoded as valid majority word.

Therefore, the best (lowest) BER value occurs when the majority vote decoder is

properly aligned with the incoming signal; that means all three word inputs are

occupied with identical (except for errors) redundant word. A linearly averaged BER

is used as the actual BER value may vary during an ALE transmission.

4.2.5.2 Signal–Plus-Noise-Plus-Distortion to Noise-Plus-Distortion Ratio

(SINAD)

This is an optional LQA measurement that calculate the SINAD

[(S+N+D)/(N+D)] averaged over the duration of the received ALE signal. It shall be

measured on all ALE signals if implemented.

4.2.6 Automatic Channel Selection

Automatic channel selection is the ability of the ALE system to automatically

identify the best channel to use when the station wants to initiate a call to another

station. In order to do this, the system refers to the most current LQA data stored in

LQA table.

The standard does not specifically state the algorithm to be used by the ALE

system to rank-order channels based on LQA data. Manufactures may use different

algorithm to rank the channels accordingly with their LQA scores. The standard only

requires that increasing numerical values should be used to correspond to increasedchannel quality and LQA scores must be displayed to the operator.



54

4.2.7 Orderwire Messages

Stations in an ALE system have the capability to transfer information within

the orderwire or message section of an ALE frame (using CMD words) including

calls, responses, and acknowledgments. This is an additional feature, which enables

operators to send and receive simple text messages within an ALE frame during

linking process. Orderwire messages include LQA, automatic message display

(AMD), data text message (DTM), and data block mode (DBM) modes.

LQA orderwire message is a mandatory feature in an ALE system. Its

purpose is to enable ALE stations to exchange currently measured LQA information

among them. Besides that, stations can also send LQA reports, which contain

previously measured LQA data rather than to report current channel measurement.

This feature however is optional. The purpose of exchange LQA results, both current

and previously is to provide each station with bilateral LQA data for these channels

in support of channel selection programs [Johnson et al, 1997].

The next message type, which is AMD is used to enable stations to

communicate short messages or prearranged codes to one or many selected stations.

All ALE stations must have the capability to send, receive and to display any

received AMD message to operators. The minimum required capacity for message is

20 characters and the maximum characters allowed are usually 400. The characters

are must use the expanded ASCII 64 subset.

DTM message type enables stations to communicate text or binary messages.

It can either be unilateral (one way) or bilateral (two-way) and it can be broadcast or

use ARQ. The purpose of this feature is for direct output to and input from associated

data terminals or other data terminal equipment (DTE) devices through their standard

data circuit-terminating equipment (DCE) ports. It is designed with improvedrobustness compared to AMD to overcome weak signals and short noise bursts.



55

DBM on the other hand is an optional oderwire message mode that is designed to

improve DTM. By eliminating the usual ALE triple redundancy in favor of deep

interleaving. The protocols and control bits for both DBM and DTM are the same.

The major difference between DBM and DTM is that DBM data are broken into

fixed size blocks before transmitted.

4.3 Summary

In this chapter, ALE was introduced and the protocols needed for it to operate are

explained based on the U.S FED-STD-1045A. The implementation of ALE may

differ from one manufacturer to another, but the basic protocols are still the same.

Protocols such as calling, scanning, sounding, LQA and automatic channel selection

are necessary in an ALE system. These protocols are responsible for making ALE

turn HF to become a more reliable medium for communications.



CHAPTER V

SYSTEM DESIGN and IMPLEMENTATION

5.1 Introduction

Information gathered from the previous chapters became the basis to build the

system for this research. This chapter explains the steps taken to develop this system.

The system was built to meet the objectives but constrained with the limitations of

the equipment.

5.2 Equipments Setup

The equipments for this system are typical HF communication equipments; HF

transceiver, HF modem with basic personal computer, the necessary accessories and

antennas. The transceiver used in this research is KENWOOD TS570D transceiver

and the modem used is Kantronics KAM’98 modem. As for the antenna, half

wavelength dipole antenna is used for all the field-testing stations. Details on theequipments are described in the following subsections.



57

5.2.1 HF Transceiver

Kenwood TS-570D is an amateur transceiver with a 16-bit DSP unit to

process audio frequencies. Figure 5.1 shows the front panel of the transceiver. The

transceiver has built-in automatic antenna tuner, which allow frequency tuning to be

done easily by just pushing a button. The transmit power of this transceiver ranges

from the minimum power of 5 Watt to maximum power of 100 Watt. Detail

specification of the transceiver is given in Appendix B.

Figure 5.1 Kenwood TS570D HF transceiver

The transceiver is connected to the computer by using 9-PIN RS-232C COM

connector as shown by Figure 5.2. The COM connecter is located at the rear part of

the transceiver. Data is sent through using a full duplex and asynchronous serial

interface. To control the transceiver, a set of computer control commands providedby the manufacturer is used. The commands, sent in ASCII formats consist of three

parts, which are the alphabetical command, parameters and the terminator. Among

the functions that can be controlled via computer are changing the frequency,

switching on/off, changing the modes of communication, changing the power and

others.

Microphone connectorSpeaker jack



58

Figure 5.2 Connection between transceiver to computer using RS-232C cable.

5.2.2 HF Modem

Kantronics KAM ’98 Multi-Mode HF/VHF Digital Terminal Node Controller

(TNC) is a modem for data transmission via HF. Figure 5.3 below shows the modem

and its connector. The modem has several teletype over radio or TOR modes: which

are AMTOR, PACTOR and GTOR with baud rate up to 300 baud [Kantronics Co.,

1998]. Other non-packet modes supported are RTTY, CW, and ASCII protocols.

Packet communication is also available using the AX.25 protocol. For this research,

the PACTOR data mode is chosen because of its reliability and robustness compared

to the other modes. Detail specifications of the modem are available in Appendix C.



60

Figure 5.4 Wiring to connect the modem and transceiver

Figure 5.5 Connection between HF modem and transceiver

Figure 5.6 shows the whole system setup. In this figure, it can be seen that the

modem is connected via the computers’ COM1 port and the transceiver is connected

via COM2.

Speaker jack

Microphone jack

Connection between HF

modem and transceiver



61

Figure 5.6 System setup

5.2.3 Dipole Antenna

The antenna plays an important role in an HF communication system. It is

responsible for radiating the electromagnetic waves into space and also does the

opposite function of receiving electromagnetic waves. There are many kinds of

antenna available today from basic wire antenna to complex and large antennas. For

this research, the chosen antenna is dipole antenna. The reason for this is because a

dipole antenna is easy to set up with minimum costs. Dipole antenna is bidirectional,

thus it can be installed in a direction so that the pattern of the radiation covers the

field-testing sites. Figure 5.7 shows a general dipole antenna.

COMPUTER

TRANSCEIVER

MODEM

POWERSUPPLY



62

Figure 5.7 Dipole antenna

The length of a dipole antenna is obtained by applying equation 5.1 below

[ARRL, 2001]:

ft F

L MHz

492= (5.1)

L is the length of the antenna, and F is the desired dipole antenna frequency.

The height of the antenna from ground is another important factor to consider whendesigning an antenna. The height determines the vertical radiation pattern of the

antenna as shown in Figure 5.8. For this research the height chosen is quarter

wavelength from the ground. Thus from frequency prediction results in chapter III,

only frequencies with elevation angle within the range of the vertical radiation of this

antenna should be use. Then Figure 5.9 shows the horizontal radiation pattern of a

dipole antenna.



63

(a)

(b)

Figure 5.8 Dipole Antenna Vertical Plane Radiation Pattern. (a) ½ wavelength high.

(b) ¼ wavelength high

Figure 5.9 shows the horizontal radiation pattern of a dipole antenna. The

grey-coloured area represents the radiation pattern of a dipole antenna. The “figure

8” radiation pattern demonstrates that signals transmitted using dipole antenna is

bidirectional [ARRL, 2001]. The four points in the figure, labeled “A” until “D”

represent several locations scattered around the antenna while the four arrows labeled

“signal I” until “signal IV” represent signals received by the antenna. Transmitted

signals using this antenna are optimum at receivers located at point A and point D

and depleted at receivers located at point B and C. The reason for this is that both

point A and point D are located within the radiation pattern of the antenna while both

points B and C are located outside the radiation pattern of the antenna. For signals

received by the antenna in Figure 5.9, signals I and II are suppressed because the



64

antenna is not sensitive in that direction. The signals III and IV are optimal because

they are received in the radiation pattern area where the antenna is sensitive.

Figure 5.9 Dipole antenna horizontal plane radiation pattern

For comparison, Figure 5.10 shows the horizontal radiation pattern for a Yagi

antenna. Yagi is a directional antenna, which means that the transmission of signals

is maximum on the main lobe which is within 120o

directions. Signals transmitted on

the sidelobes and backlobe suffers energy loss, thus must be avoided [Carr, 2001].

As a receiver, by referring to Figure 5.10, signal I is received the loudest, while

signals II, III and IV are suppressed. Thus, to use this type of antenna, the direction is

very important. The antenna must be placed in the direction so that the main lobe is

facing the direction of the receiver. On the other hand, for dipole antenna, as long as

the destination station is situated in the “upper” or “lower” region from the dipole

antenna, it will be covered by the antenna radiation pattern. For example, consider

point A in Figure 5.10. If the antenna is moved 60o

from its original position, signals

transmitted cannot be received y point A and vice versa. This is the reason why



65

dipole antenna is chosen to be used in this research instead of Yagi as antenna

direction is not so critical for a dipole antenna compared to Yagi.

Figure 5.10 Yagi antenna horizontal radiation pattern

The construction of dipole antenna installed at the DSP lab, Universiti

Teknologi Malaysia, located in Skudai, Johor is shown Figure 5.11. The antenna was

built using the normal single core wire that is usually used for grounding electrical

appliances. The antenna is fed in the middle where coaxial cable is used as the

feeder. An insulator which is made from wood is used separates earth and live wires.

Insulators are also used to separate rope and wires. To maximize the effective

forward transmit power from the transmitter to the antenna, transceiver is placed

close to the antenna so that the feeder line is as short as possible.



66

Figure 5.11 Construction of dipole antenna

Figure 5.12 shows the antenna installed in at DSP lab in UTM. It is designed

for 7 MHz, so by using the formula shown in Equation (5.1), the length of the

antenna is approximately 80 feet. The antenna is 40 feet (approximately 12 meters)

high from the ground.

Figure 5.12 Dipole antenna at DSP Lab, UTM



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5.3 System Design

Choosing the best frequency is critical in HF communication to ensure reliable

performance. Thus, the designed messaging system in this research is equipped with

ALE capability which will automatically select the best frequency to be used. To

achieve this purpose, the design methodologies are listed as follows

i) Design methods to automatically control the HF radio transceiver and

modem.

ii) Develop the messaging system which can transmit data via HF

iii) Design and Implement ALE protocols in the messaging system for

calling, sounding, link quality analysis (LQA) and scanning.

iv) Develop ALE database, which holds the results from ALE soundings.

Figure 5.13 shows the flowchart of the system. At start up, the system

perform initialization, which is a process where previous channel evaluation data are

uploaded. After performing initialization, the system stays on the best channel

(according to the uploaded data) and listens for any incoming call or sounding. When

the station wants to link to another station, ALE linking protocol will be applied. The

same goes if a station receives link request from another station. The link request will

be handled by ALE linking protocols.



68

Figure 5.13 System flowchart

At predetermined time interval, the system performs real-time channel

evaluation by doing sounding and LQA automatically to determine the best channel

for that hour. To do this, a string known as sounding frame is sent to the destination

station. Meanwhile, station that is not scheduled to perform sounding will scan its

entire five channels one by one, listening for any sounding frame. Once the sounding

frame is detected, destination station performs LQA on that frame. After the

sounding is completed for all five channels, both stations stay and listen on the best

channel until the next sounding occurs.



69

5.3.1 PACTOR Data Format

The data format chosen for this research is PACTOR mode that is used for

messaging and ALE purposes. PACTOR or Packet Teleprinting Over Radio

[Kantronics Co., 1998] is a modern radio Teletype data mode developed to improve

inefficient modes such as AMTOR. PACTOR is a half-duplex synchronous ARQ

system designed to operate in noisy channels. The features offered by PACTOR are

[Riley, 1997]:

i) PACTOR has the capability of automatic speed change between 100 baud

(on noisy channel) and 200 baud (on clearer channel)

ii) Fixed timing structure, where the entire cycle length is 1.25 seconds and

the packet length is 0.96 seconds. The timing details for PACTOR are as

follows

Cycle duration: 1.25 seconds

Packet length: 0.96 seconds = 192 bits at 200 baud or 96 bits at

100 baud

Control signals: 0.12 seconds= 12 bits, each 10 msec long

CS receive gap:0.29 second

iii) The PACTOR packet data format consists of three sections which are the

header, data and control as shown below

/header/………..data bytes……../controls/

The size of data field depends on the baud rate. When the baud rate is

100, the data field is 64 bits (8 ASCII characters) but it increases to 160

bits (20 ASCII characters) if baud rate is 200. The control field consists of

system control byte and 16-bit cyclic redundancy check (CRC). For

acknowledgment, the short control signals (CS) sent out by the receiving

station is 12 bits long.



70

iv) To enhance the error correction capability, PACTOR have memory ARQ

feature that enables noisy packets to be restored.

5.3.2 ALE Protocols

ALE is the set of protocols in the system used to handle the linking and

selecting the best channel processes. The ALE protocols are as below

i) Linking

ii) Sounding

iii) LQA

iv) Scanning


The most basic ALE structure consists of two parts, which are preamble and

call sign as shown below in Figure 5.14. Preamble is a two characters string, which

determines the type of ALE structure. There are two types of preambles, which are

“2O” and “5O”. Table 5.1 shows types of preambles and their functions.

Figure 5.14 Basic structure of ALE

PREAMBLE(2 CHARACTERS)

CALLSIGN(8 CHARACTERS)



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Table 5.1 Preambles and their functions

Preamble Function

2O Used in calling cycle part of a frame.

To identify the destination station address.

5O Used as a conclusion of a frame

To identify the source station address.

There are four types of ALE frames, which are the calling frame, response frame,

acknowledgment frame and finally sounding frame. Each frame as shown by Figure

5.15 consists of two parts, which are the calling cycle and conclusion except for

sounding frame, which only consist conclusion. The type of preamble used

distinguishes calling cycle from conclusion. As seen in table 5.1 above, for calling

cycle, “2O” preamble is used, followed by the call sign of the destination. The

calling cycle is then repeated as necessary. The number of repetition depends on

whether the frame is for calling, response or acknowledgment purpose. In a call

frame, the calling cycle is repeated 3 times before the conclusion take place. For both

the response and acknowledgment frames, the calling cycle is only repeated twice.

Calling, response and acknowledgment are the frames are used in linking process.

Figure 5.15 General structure of an ALE frame

The conclusion on the other hand is made up from “5O” preambles and source

station call sign. Conclusion is important because it identifies the station sending the

ALE frames. Calling, response and acknowledgment frames, contain one conclusion

part. However for sounding frame, conclusion is repeated five times and does not

need calling cycle. This is because the sounding frame is not for linking process; it is



72

just a one-direction signal that is used by the receiving station to evaluate the channel

performance.

5.3.2.2 Linking to Another Station

The flowchart in Figure 5.16 shows the summary of the process to establish a

link for both calling and destination stations. If a station (source station) wishes to

establish a link to another station, it must first send a call frame to the destination

station. After sending call frame, the source station disables sounding and scanning

and waits for response from the destination station within a limited wait-for-response

time (Twr). For this system, Twr is set to 2 minutes. If the source station did not

receive any response after Twr ended, the call is considered unsuccessful. The source

station will have to send another call frame if it wishes to link again.

Figure 5.16 Flowchart for link establishment

The destination station, upon receiving the call frame will examine the

validity of the frame. A valid call frame is a frame that consists of calling cycle,repeated three times. If the received frame is a valid call frame, a response frame will



73

be generated and sent to the source station. Like the source station, the destination

station also disables sounding and scanning. It then starts its own wait time, Twr to

wait for acknowledgment from the calling station. If the destination station did not

receive any acknowledgment frame from source station, it considered the call as

unsuccessful. It will then return to listen mode and enable sounding and scanning.

Immediately after receiving the response frame, source station send

acknowledgment frames and therefore the link has been established. Both stations

can now communicate with each other until either one of the station terminates the

link. After the link is terminated, both stations enable sounding and enter listen

mode. Figure 5.17 shows the call, response and acknowledgment frames.

Figure 5.17 Call, response and acknowledgment frames

5.3.2.3 Sounding and Link Quality Analysis (LQA)

The most important ALE protocol in the system is sounding because it

determines which is the best channel to use for communication. Sounding is done

periodically at predetermined time selected beforehand by the user. Both stations

must select different sounding time to avoid sounding to occur at the same time. Two

sounding time choices are available which are either every 15 minutes on each hour

Note:DEST= destination station call signCALL= source station call sign



74

or 30 minutes on each hour. Choosing 15 minutes of an hour means that sounding for

that station is scheduled at 15 minutes past every hour such as at 10.15 a.m., 11.15

a.m., and 12.15 p.m. and so on. On the other hand, choosing sounding time of 30

minutes will cause the system to perform sounding at every 30 minutes past the

hours. Meaning that sounding, for that station will occurs at 10.30 a.m., 11.30 a.m.,

and 12.30 p.m. and so on.

Sounding frame consists only conclusion cycle, repeated five times as shown

in Figure 5.18. Sounding is performed by transmitting sounding frame to the

destination station. After transmitting the sounding frame, sounding station waits for

acknowledgment from the destination station in its wait period, Twr. The value of Twr

is 2 minutes. If no acknowledgment is received after Twr., the sounding is considered

unsuccessful. Thus if this situation occurred, a large default value of 1000 will be

attach as the score for that channel.

Figure 5.18 Sounding frame

The destination station, upon receiving the sounding frame, analyzes the

sounding frame and then performs LQA. Then it sends acknowledgment to the

sounding station. Acknowledgment is a short frame consisting of a flag character and

LQA result for the current channel. The purpose of the flag is for synchronization

between the two stations. The flag is set to either “1” or “0”. Assigning the flag value

to“1” is to let the sounding station knows that the sounding is acceptable and the

destination station will proceed and ready to receive sounding on the next channel.

Sounding station saves the LQA results, and proceeds to the next channel to repeat

the sounding process again. This process continues until the entire five channels have

been sounded. When sounding process reached the last channel, the flag value is set



75

to “0”. Both stations will then perform the process of ranking the channels based on

LQA scores. The results are then saved in ALE database located in the hard disk.

Then both stations change their transceiver frequency to the highest-ranking channel

according to the latest result and stay there until the next sounding process occurs. So

by doing this, the stations can now communicate on the best channel for that hour.

The flowchart for sounding process is shown by Figure 5.19.

Figure 5.19 Sounding process

During sounding, the modem divided sounding frames into several packets

before transmitting them. The time it takes for a PACTOR data packet to arrive to

destination is 0.96 second (assumed equal to 1 second). If this packet is error-free,

the destination modem will send it to computer and displayed on the computer

screen. However, if a packet arrives at the destination contains error; the destinationmodem will not send the packet to the computer. Instead, it will acknowledge the



76

sender about the error and request for retransmission. The sender modem will then

retransmit the packet. After another second, the retransmitted packet arrived at

destination. If the packet is error-free, it is accepted, but if it still contains error, the

receiver will ask for it to be retransmitted again. This procedure is repeated until the

packet received by the destination station contains no error. Therefore, it can be

concluded that the process of retransmitting packet increase the time it takes for

error-free packet to arrive at destination. So, if the time taken for a complete error-

free packet to arrive at destination is more than 1 second, retransmission has

occurred. The longer the time it takes for an error-free packet to arrive indicates that

many retransmissions have occurred. Thus, this means that the channel is bad.

Taking advantage of this fact, LQA scoring is done by counting the number of

second it takes for a complete error-free sounding frame to arrive at destination.

LQA score counting starts when the first character of a sounding frame

arrived at the destination. The destination station records the number of second it

takes for the first packet to arrive. This value becomes the LQA score for that packet.

If the time taken is one second, which indicates no retransmission occurred, the LQA

score is set to zero. When the second packet arrives, the LQA score for that packet is

obtained by following the same procedure as the first packet. Then the LQA score of

the first packet and second packet are then added to obtain the total LQA score. This

process is repeated for the third and the rest of the packets until a complete sounding

frame arrive at the destination station. The total LQA scores of all the packets,

becomes the LQA score for that channel. The scores are then averaged with the

scores from previous hour and then averaged once again with the scores from

previous day. This is because of the fact that HF propagation varies within every

hour and with days. Averaging the scores will contribute to a more consistent and

steady results. After that, the destination station saves this score and sends it to the

sounding station via the acknowledgment frame. Both stations proceed to the next

channel and repeat all the steps above until all five channels have been sounded.

However, if the condition of the channel is very bad, it can cause sounding to fail and

a large default value of 1000 will be attach as the score for that channel.



77

After the sounding and LQA scoring process for each channel has been done,

both sounding and destination stations will proceed to the next step, which is ranking

the channels. Ranking is done by comparing the LQA scores for each channel.

Channel with the smallest number of LQA score is determined as the best channel.

Then, channel with the second lowest score is rank as the second best channel and so

on until the last channel is determined. To better understand the process of LQA and

channel ranking, consider the sample results in Table 5.2.

Table 5.2 Example results of LQA

Channel no Frequency (MHz) LQA score Channel ranking

1 8.002 2 3

2 8.190 0 1

3 8. 710 0 2

4 9.108 7 5

5 10.100 5 4

From the result in table 5.2, it can be seen that channel 1 has LQA score of 2

while both channel 2 and channel 3 has zero LQA score. Channel 4 has LQA score 7

which is the highest score, and finally channel 5 has LQA score of 5. Thus according

to the table, it can be seen that channel 2 and channel 3 are the highest-ranking

channels. However, for simplicity, if two or more channels have same LQA score,

the channels will be ranked according to its channel number. For instance, in this

example, although the score for channel 2 and 3 are the same, channel 2 is ranked as

the first channel and channel 3 as the second best channel. The third best channel is

channel 1, followed by channel 5. Lastly, the worst channel, ranked 5th

is channel 4.

5.3.2.4 Scanning

The purpose of scanning is to enable the station to detect sounding frame sent

by the sounding station. It is to ensure that the destination station will be able to



78

receive the sounding frame and perform LQA on other channel if sounding for

channel 1 fails. At every hour, the system automatically starts scanning one minute

before the expected sounding time of the other station. For example, consider

stations A and B with sounding time 15 and 30 minutes of an hour respectively. For

example, it is 10.14 a.m., thus station B will begin scanning process looking for any

sounding frame on each channel. The dwell time, which is the time a station stays

and listens on each channel, is 10 seconds, making the total scan cycle is 50 seconds.

The destination station keeps on scanning until a request for sounding is

detected. Then the scanning process will stop and the destination station will process

the sounding frame. Scanning is disabled for an hour, until it is time for the other

station to do sounding again. However, a user can also direct the system to perform

scanning by choosing “start scan” in the “scanning” menu.

5.3.2.5 ALE Database

The database for this system was built using Microsoft Access. The name of

the database is “Ale.mdb” and it consists of three main tables, which are the Info

table, the LQA table and finally the Test table. Each table contains results and

information from soundings of all five channels for every hour. Among the

information includes, the call signs for both stations, the channel used, the LQA

scores and channel ranking. The purpose of saving the results in a database is

because the past sounding results are used in LQA scoring process to determine the

present LQA result. Besides that, graphs can be plotted based on the data kept in the

database to view and summarize the performance of each channel for a given period

of time. In addition, the results are also accessed by the system during initialization

process. Table 5.3 explains the purposes and data contained in each table in the

database.



79

Table 5.3 Tables in ALE database.

Table name Purpose Data

Info Saves the information of the

stations

Date and time

Station’s call sign

Channels used by the station

Location of both stations

LQA Hold the results of current

sounding for every hour

Date and time

Sounding time slots

Scores for each channel

Ranks for each channel

Source of sounding

Test Contains the final sounding

results for each hour i.e. the

averaged results

Date and time

Sounding time slots

Scores for each channel

Ranks for each channel

Source of sounding

5.3.2.6 Comparison with Standard ALE Systems

The protocols listed above are different from the protocols in FED-STD-

1045A [NCS, 1993]. The reason for this is because the ALE implemented in this

research is constraint to the type of transceiver and most importantly the type of

modem used. Therefore, all the ALE protocols used in this research must be made

accordingly with the transceiver and modem. The major difference is that in FED-

STD-1045A, ALE is implemented as separate equipment while ALE in this research

is developed as software. Other differences are as listed in Table 5.4.



80

Table 5.4 Comparisons of ALE

Features ALE based on [FED-STD-

1045A, 1994]

ALE implemented in this

research

Modulation Uses 8-ary FSK modulation

with eight orthogonal tones,

one tone (or symbol) at a time

AFSK modulation

Coding Extended (24,12,3) Golay code

is use. Thus FEC is

implemented.

Uses PACTOR data mode, which

implement ARQ error correction.

Multiple

stations

Multiple stations operation is

enabled.

No multiple stations operation

available. Only point-to point

connection is available.

Scanning Scanning is done continuously,

with scan rate of either 2

channels per second or 5

channels per second.

Scanning is only done once every

hour. The dwell time is 10 second

for each channel; thus the total

scan cycle is 50 seconds. Scan rate

is 1/10 channel per second.

5.3.3 Graphical User Interface (GUI)

The messaging system’s user interface is shown on Figure 5.20. From the

start up window, user enters the necessary information for that session, which are call

signs for terminal and destination stations, the location of stations, the sounding

interval and also the channels to be used. If user wanted to enter a new set of

channel, “New Channels” option should be selected. The user then needs to enter the

desired frequencies to be used. Up to five channels can be selected during a session.

For optimum results, the selection of channels should be based upon the results of

frequency predictions as explained on Chapter III. If on the other hand, user wants to

use the same channels used in the previous session, “Load Previous Channel” option



81

must be chosen. After entering the necessary data, user must click ok. Then the main

user window will appear.

Figure 5.20 User interface for the system

Start-up window

Terminalproperties

Receivedmessages

S stem status

Load previous channels

New channels

Channels

Destinationproperties

Soundingtime

Start system – load data

Link

Unlink

Reset system Settings

Return tocommand mode

Change stationscall signs

Changesounding time

Changechannels

System menus

Send message

Main window

transmit messagestext box

Start up window



82

On the main window, all the properties and settings during the sessions are

displayed on the left part of the window. Before starting a session, user must first

perform initialization by clicking the “Start” button. The purpose of initialization

process is to load the most recent sounding result including channels ranking so that

the system stays on the best frequency. Then the system will stay in listen mode until

it is time to perform sounding or a user wants to link to destination station. Table 5.5

shows the functions available on the GUI and their descriptions.

Table 5.5 Functions available on the system’s GUI

Function Descriptions

Link / unlink To establish link with another station, user must click on “Link”

button. If the link is established, a message will be displayed on

the “Receive” textbox.

To disconnect the link, user must click on the “Unlink” button.

Reset system The “Reset” button can be used when a user wants to reset the

system. By doing this the system clears its buffers and return to

initial condition. User then must click the “Start” button to

perform initialization.

Change setting User can change all the settings at anytime by two ways:

• One way is by clicking change “Change” buttons

provided at the corner of each property boxes.

• Another way is by clicking the “Setting” button which

will display a properties window. This is where user can

change all the settings for this session.

Return to

command mode

To return to the modem’s “command” mode; a mode where

commands are send to the modem, user must click on the

“Command” button. The modem is now in command mode. A

pop-up window will appear where user can enter the desired

command and then click OK.



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Send message When in linked mode, if a user wants to send message, the user

must first type the message in the “Transmit” textbox then click

“Send” button.

Send file To send a text file, user must click the “File” menu, and then

click open. A file browse window will appear. After selecting

which file to be sent, user must click OK and the file will be

send.

Save message User can save received message by clicking “Save” in the “File”

menu. The message will be saved as a text file.

Start Sounding To force the system to start sounding, user can click on

“Sounding” menu and then select “Start”.

Disable

Sounding

A user can also disable sounding by selecting “Stop” on

“Sounding” menu.

Start Scanning As with sounding, user can also force the system to start

scanning by clicking on “Scanning” menu and then click on

“Start”. To stop scanning, click “Stop” on the same “Scanning”

menu.

5.4 Summary

This chapter explained how the system is designed and implemented to achieve

the objectives. This chapter covers two topics, which are equipments setup and

design of the system. In equipments setup, overview of the equipments used in this

research is explained. HF transceiver, HF modem and personal computer are the

building blocks of this system. Another important factor explained in this topic is the

antenna used for this research. Selecting the suitable antenna is very important in HF

communication because if the unsuitable antenna is used, can lead to unreliable

communication.



84

Then the discussions move to the system design topic, which mainly explain how

the system is implemented. The system designed not only operates as a messaging

system but also as an ALE system that selects the best channel for communication.

The system is then tested to verify its performance. The results of the field-testing are

described in the next chapter.



CHAPTER VI

FIELD TESTING RESULT

6.1 Introduction

This chapter covers the field-testing conducted for this research. The explanation

focuses on the procedures and the result obtained from the field-testing. Field-testing

is a vital step in this research as it verifies the system performance in real-time

situation. This chapter explains about the selection of field-test sites and the reasons

why these sites were chosen. The details on each station such as location, distance

and system setup are also explained. Then the results are presented and discussed.

From the daily results, the most suitable frequencies to use throughout the field-

tesing period is determined. Finally, the results from field-testing are compared with

predicted Optimum working frequency (OWF) results from Chapter III.



86

6.2 Test Equipments Setup

The equipments setup for both local and remote stations is shown on Figure

6.1. From the figure, it can be seen that both transceiver and modem are connected to

a computer. Both stations used the same type of equipments and antennas. The

messaging system installed in the computer controlled both transceiver and modem

to enable point-to-point connection between the local and remote station. For all the

field-testing conducted, Skudai was chosen as the local station. Each station has

unique call signs that were used as identification in the messaging system.

Figure 6.1 Equipments setup for field-testing

The next step was setting up the transceiver. The first step is to set the

transceiver to LSB mode. Then the FSK filter in the transceiver was also set and the

bandwidth value chosen was 300Hz. By setting this, the built-in band pass filter

inside the Kenwood HF transceiver to reduce noise is utilized. Then all five chosen

frequencies are tuned using the transceiver’s built in tuner to ensure maximum power

transfer during transmission. Then the transmit power level of the transceiver is set to

the most suitable value. During the field-testing conducted, the transmission power

used in this field-testing is from 10 to 20 Watt.



87

6.3 Selection of Field-Test Sites

Field testing sites for this research are selected based on two conditions. The

first condition is that the distance between the transmitter and receiver station must

be located more than 100 kilometers away from each other. This is necessary to

exclude the line of sight signal components from reaching the receiver. In other

words, to let the stations communicate via sky wave propagation. The second

condition is that the location of the field-testing site must be within the antenna

radiation pattern. Two test sites are selected for this research, which are Kota Bahru

in Kelantan and Chemor in Perak. The station in UTM Skudai Campus becomes

local station while the two other stations are remotes sites. Figure 6.2 shows the

location of both field-testing sites.

Figure 6.2 Location of field testing sites with estimated antenna

radiation pattern



88

From chapter V, the antenna in Figure 5.9 is placed at 0o to 180o. If 90o is

north, then 0o

is east, and 180o

is west. Thus, it can be seen that the radiation pattern

of dipole antenna placed at east-west direction can cover the area in the north and

south region. The antenna installed in Skudai is positioned in the east-west direction,

which makes the signals transmitted from this antenna radiates in north and south

directions. Therefore, the locations of field-testing sites, which are Kota Bahru and

Chemor are covered by the radiation pattern of the antenna. This is shown in Figure

6.2 where the estimated antenna radiation pattern for Skudai, Kota Bahru and

Chemor are illustrated. From this figure, it can be seen that since the locations of the

field-testing sites are in the northern region of peninsular Malaysia, the antenna must

be positioned in east-west directions so that the transmitted signals can reach the

local station, which is Skudai. If the antenna in any of the locations is placed in

different directions, the signal radiated from the antenna may not reach Skudai

station. For example, the antenna in Chemor is placed in north-south direction, thus

the radiation pattern would be in the east-west direction, making it almost impossible

to communicate to Skudai.

6.3.1 Kota Bahru

The first field-test site; Kota Bahru is located approximately to the north of

Skudai, with straight distance of 535 km. The testing between Skudai and Kota

Bahru was conducted from 11th until 24th of March 2005. Figure 6.3 shows the

equipments setup at Kota Bahru station. Then Figure 6.4 shows the antenna setup at

that station. The antenna used at this station was half wavelength dipole, the same set

up as in Skudai with ¼ wavelengths high above the ground. The antenna was

installed in east to west direction, so that the horizontal radiation of the antenna is

towards the north and south.



89

Figure 6.3 Equipments Setup at Kota Bahru Station

Figure 6.4 Antenna Setup at Kota Bahru

Computer

Modem

Transceiver

Power supply

Live

Earth

Feeder cable



90

6.3.2 Chemor

Chemor is situated at about 452 km to the north-west of Skudai. Figure 6.5

shows the equipments setup at this station. Next, Figure 6.6 shows the antenna setup

at this station. Here, as in Kota Bahru, a half wavelength dipole antenna is used. The

height of this antenna is about 20 feet from the ground, which is approximately equal

to ¼ wavelength. Like the antenna setup in Kota Bahru, this antenna is also placed in

east-west direction so that signal radiation can cover up to the station in Skudai.

Figure 6.5 Equipments Setup in Chemor



91

Figure 6.6 Antenna Setup at Chemor

6.4 Channels Selection

Two factors were considered for selecting the five channels used in each

field-test. The first factor is considering the results obtained from ASAPS frequency

prediction as shown in Chapter III. Based on the result, frequencies that are available

on 50% to 90% of the days in a month were chosen. Mainly, frequencies that closer

to the OWF are considered first. After that, frequencies between the MUF and OWF

on most of the time during the days are considered. Frequencies below and near the

ALF are avoided. Another factor considered when choosing which frequencies to use

is the frequency allocated by the experimental license. The license, awarded by the

Malaysian Communications and multimedia Commission (MCMC) is shown in

Appendix D. There are up to 15 carrier frequencies allocated in the license that can

be used. Therefore, the field-testing used as close as possible the frequencies

allocated in the license.

Live

Earth

Feeder cable



92

For a given circuit, both local and remote stations used the same sets of

frequencies throughout the field-testing period. Table 6.1 below shows all the

frequencies used by the circuits in both field-testing.

Table 6.1 List of channels used in field-testing

Channel no. Skudai-Kota Bahru channels

(MHz)

Skudai-Chemor channels (MHz)

1 8.002 8.190

2 8.190 7.100

3 8.710 8.710

4 9.108 8.002

5 10.100 9.200

6.5 Field-testing Timeslots

For ALE sounding purposes, the time of day is divided into four timeslots

which represents morning hours, afternoon hours, evening hours and midnight until

early morning. For example, timeslot 1 which is between 7.00 a.m until 11.59 a.m,

are morning hours while from 12 noon until 6.59 p.m. belongs to timeslot 2. Table

6.2 below shows the allocation for all four timeslots. The changes of the ionospheric

condition between hours in the same timeslot are minor, but between the timeslots,

the changes are significant. Therefore, the sounding results between hours in the

same timeslot are summarized. Then by comparing the sounding results for each

timeslot, the effects of changes in ionospheric condition on HF propagation can be

seen. Another reason of dividing the day into timeslots is to make it easy for

representing the results in form of graphs. The LQA results of each hour in the same

timeslots are averaged with the previous hour results, thus producing a single set of

LQA result for each timeslots. The reason for doing this has been explained in

Chapter V.



93

Table 6.2 Timeslots allocation

TIMESLOT DURATION

1 From 7.00 a.m. until 11.59 p.m

2 From 12.00 noon until 6.59 p.m.

3 From 7.00 p.m. until 12.59 a.m.

4 From 1.00 a.m. until 6.59 a.m.

For Skudai-Kota Bahru field-testing, data is colleted daily in the morning,

afternoon and at night. This means that field-testing is conducted for timeslots 1 until

timeslot 3. The hours allocation for timeslots are as follows:

i) Timeslot 1: From 10.00 a.m. to11.59 a.m.

ii) Timeslot 2: From 3.00 p.m. to 6.00 p.m.

iii) Timeslot 3: From 8.00 p.m. to 11.00 p.m.

Skudai-Chemor field-testing is conducted for timeslots 1 until timeslot 2

only. Everyday, data is collected according to the schedule below.

i) Timeslot 1: From 9.00 a.m. to1200 noon

ii) Timeslot 2: From 2.00 p.m. to 4.00 p.m.

6.6 Results and Discussions

The LQA scoring applied in this research is different from the LQA scoring

in U.S Federal Standard 1045A [NCS, 1993]. In the Federal Standard 1045, the error

control method used for transmitting ALE words is Golay forward error correction

(FEC) code, thus the LQA is done by obtaining the bit error ratio or BER of the

transmitted ALE frame. The ALE frames in this research are transmitted using



94

PACTOR data format, which uses Automatic Repeat Request (ARQ) error

correction. Thus, BER method cannot be apply in order to determine the LQA score

for a channel. To overcome this problem, as explained in the previous chapter, LQA

score is obtained by counting the number of seconds it takes for a complete error-free

sounding frame to arrive at destination. Moreover, the standard does not state any

rule or requirements on the algorithm used by ALE system to rank-order the channels

based on LQA data. Different ALE system may employ unique innovative

techniques to perform LQA and channel ranking [Johnson et al, 1997].

The database containing full results from field-testing are presented in

Appendix E for Skudai-Kota Bahru field-testing and in Appendix F for Skudai-

Chemor field-testing. Among others, the database contains LQA score for soundings

of each channel and also the ranking of the channels at every hour. Then, the results

from the database are summarized and presented in form of graphs. Two graphs are

plotted for each timeslot. The first one is a graph of LQA results for each channel

versus date. Then the second graph is a graph of ranking of each channel versus date.

From the plotted graphs, analysis is done to determine the best channel to use for

each timeslot throughout the field-testing period by comparing the performances of

the channels everyday. There are two steps taken to compare the performance of each

channel. The first step is by comparing the LQA scores of each channel. In general,

the channel with the most number of low LQA score days during the field-testing

period is considered as the best channel. High LQA score on the other hand indicates

that many retransmissions have occurred, which means that the frequency is bad.

There are four categories of LQA score available, which are zero LQA score, low

LQA score, medium LQA score, high LQA score and finally very high LQA score.

The range of LQA scores for each category is shown in Table 6.3.

To select the best usable channel during the field-testing period, by referring to

LQA score graph, factors listed below are considered:

i) The number of days that LQA scores are zero.ii) The number of days that LQA scores are low.



95

iii) The number of days that LQA scores are medium.

iv) The number of days that LQA scores are high.

v) The number of days that LQA scores are very high.

vi) The lowest and highest score for each channel.

Table 6.3 LQA Score categories

Score LQA score Range Remark

Zero 0 This is the lowest score. This score indicate that the

sounding frame packets transmitted contain no error.

The channel propagation condition is therefore very

good and channel with this score is the best channel to

be used for communication.

Low From 1 to 5 This score indicate that the sounding frame packets

transmitted contain minimum error. Thus, this means

that the packets are retransmitted a few times. The

propagation condition for channel with this score is

considered good and can be used for communication.

Medium From 6 to 15 This kind of score is a result from several

retransmissions of packets of sounding frame. Thus the

channel condition is not so good. However,

communication can still be done using this channel.

High From 16 to 25 This score indicates many retransmissions of sounding

frame packets have occurred. This channel is therefore

considered bad. Communicating using this channel has

low chance of succeed.

Very

high

From 26 onward Channel with this score must be avoided. This score

indicates two possibilities: either the number of

retransmission is very high or the sounding fails for

this channel. Thus the condition of this channel is very

bad.



96

The second step is to evaluate the performance of each channel is by

examining the channel-ranking graph. By referring to channel ranking graph, factors

below are considered:

i) How many days the channel is ranked as the best channel.

ii) How many days the channel is ranked as the worst channel.

iii) The position the channel is usually ranked and how many days it takes

that position.

After considering the factors stated above, and comparing the performance of

each channel, the best channel throughout the field-testing period for each timeslot is

known. The subsections below explain the analysis and summary of each field-

testing result. Then the results are compared with predicted frequencies from ASAPS

prediction program shown in Chapter III.

6.6.1 Skudai-Kota Bahru Result

Field-testing for Skudai-Kota Bahru circuit was done daily from 10.00 a.m. to

11.00 p.m. The hours were divided into three timeslots as explained earlier in this

chapter. During each timeslot, sounding is done hourly according to its

predetermined sounding time. The LQA results of the sounding done are explained

below.



97

6.6.1.1 Sounding Results During Timeslot 1

For each hour in the timeslots as stated above, both stations performed

sounding once at predetermined sounding time. For Skudai, sounding occurred at 15

minutes past every hour, for example at 10.15 a.m., 11.15 a.m., 12.15 p.m and so on.

Kota Bahru station on the other hand performed sounding at every 30 minutes past

the hour (at 10.30 a.m., 11.30 a.m., 12.30 p.m. and so on).

i) Sounding Made by Skudai Station.

The graph in figure 6.7 below shows the LQA result for sounding sent by

Skudai station from 17th

March until 24th

March 2005. In this graph, the LQA score

for each channel are represented in a form of bar graph. The score ranges from 0 to

43 and different colours are used to represent each channel. Then on figure 6.8 the

graph of channel ranking versus date is shown. Ranking for each channel throughout

the field-testing period in this figure is shown in a form of line graph.



98

Figure 6.7 LQA result for sounding made by Skudai station during timeslot 1

Figure 6.8 Channels Ranking for Sounding by Skudai During timeslot 1

0

5

10

15

20

25

30

35

40

45

03/17/2005 03/18/2005 03/19/2005 03/20/2005 03/21/2005 03/22/2005 03/23/2005 03/24/2005

Date

S c o r e

channel 1: 8.002MHz channel 2: 8.190 MHz channel 3: 8.710 MHz channel 4: 9.108 MH z channel 5: 10.100 MHz

0

1

2

3

4

5

6

03/17/2005 03/18/2005 03/19/2005 03/20/2005 03/21/2005 03/22/2005 03/23/2005 03/24/2005

date

R a n k

channel 1: 8.002MHz channel 2: 8.190 MHz channel 3: 8.710 MHz channel 4: 9.108 MHz channel 5: 10.100 MHz



99

Based on results presented by both Figure 6.7 and 6.8, analysis is done. The

purpose of this analysis is to determine which channel has the most low score days as

this is the best channel during this timeslot. The analysis results are shown in Table

6.4. In this table, the LQA results in Figure 6.7 are sorted according to LQA score

categories as shown in Table 6.3 which are zero, low, medium, high and very high

LQA score. Therefore, for each channel, the number of days for each score

categories is known. Then by referring to Figure 6.8, the number of days each

channel became the best and the worst channel is identified.

Table 6.4 Skudai-Kota Bahru Result Analysis for Sounding made by Skudai during

timeslot 1

LQA Score RankDays

Channel Zero Low Medium High Very high first last

1 4 2 3 0 0 6 0

2 5 2 1 0 0 2 0

3 2 2 3 0 1 0 2

4 2 3 3 0 0 0 1

5 1 3 4 0 0 5

According to analysis results in Table 6.4, we can see that channel 2 which

is 8.190 MHz is the best channel because it has the most number of days with zero

LQA score. Zero LQA score for this channel occurred for five days. Other than that,

this channel has two low score days, on 18th

and 24th

and a medium LQA score day

on 23rd

March, where the score is 7. This is also the highest score for this channel.

The second best channel is channel 1, which is 8.002 MHz. This channel has four

zero LQA score days and two low LQA score days. Other than that, it also has two

medium score days on 19 and 23 March. Although channel 2 is the best channel, but

based on the channel ranking graph in Figure 6.8, it can be seen that channel 1 is

ranked as the best channel for six days, while channel 2 is ranked as the best channel

only twice. This happens because based on the LQA score graph in Figure 6.7, on

17th

, 20th

and 21st, the score for both channel 1 and 2 are same which is zero. Thus

channel 1 and 2 are the best channel for those days. However, the system, for



100

simplicity has ranked channel 1 as the best channel and channel 2 as the second best

channel. Nonetheless, for overall results, channel 2 is determined as the best channel;

because it has more number of days with very low scores than channel 1. Besides

that, the highest score for channel 2 is 7, while channel 1’s highest score is 15.

The next best channel to consider is channel 4, which is 9.108. Compared to

the two best channels, this channel only has two days with zero LQA score. For the

rest of the days, this channel has three low and medium LQA score days. The highest

score for this channel is 7 which occurred on three days from 21st

until 23rd

March.

Based on the results, this channel is ranked as the third best channel for this timeslot.

According to Figure 6.7, channel 3, which is 8.710 MHz, has the same number

of zero LQA days as channel 4 which is two. Channel 5, which is 10.100 MHz, on

the other hand only has one zero LQA score day. However, the number of low LQA

score days for channel 5 is three, which is higher than channel 3 with two days.

Moreover, channel 5 also has more medium LQA score days than channel 3. Plus,

the highest score for channel 3 is above 40 while the highest score for channel 5 is

15. Thus, channel 5 is the fourth best channel and channel 3 is the worst channel.

ii) Sounding Made by Kota Bahru Station.

The next step now is to analyze the results of sounding made by Kota

Bahru station and recorded by Skudai. The LQA score from sounding made by Kota

Bahru are illustrates on Figure 6.9, followed by the graph showing the ranking of

each channel on Figure 6.10. Then the analysis of both graphs in Figure 6.9 and

Figure 6.10 are shown in Table 6.5.



102

Table 6.5 Skudai-Kota Bahru Result Analysis for Sounding made by Kota Bahru

during timeslot 1

LQA Score RankDays


1 3 3 2 0 0 5 0

2 5 1 2 0 0 3 0

3 4 0 4 0 0 0 0

4 1 3 4 0 0 0 2

5 2 1 5 0 0 0 6

Similar to sounding from Skudai, the best channel for timeslot1 for sounding

made by Kota Bahru is channel 2, followed by channel 1. For channel 2, the LQA

score on the first five days were zero. Then on the 6th

day, the score is 2 which is a

low LQA score. For the rest of two days, the score becomes medium. For channel 1

on the other hand, there are only three days with zero LQA score. This channel also

has three low LQA score days and two medium score LQA days. The highest score

for this channel is 7, which occurred twice, on 22nd

and 23rd

March. By referring to

Channel ranking graph, it can be seen that channel 1 becomes the best channel 5

times while channel 2 becomes the best channel three times. Both channel never

became the worst channel throughout the field-testing period.

The third best channel according to Figure 6.9 and Figure 6.10 is channel 3.

Although compared to channel 1, this channel has more zero LQA score days (four),

but it has no low score days. Moreover, this channel has four medium LQA scores

days and the highest score is 15. According to channel ranking graph in Figure 6.10,

this channel has never been ranked as the best or the worst channel. It is ranked as

the third best channel most of the time.

From Figure 6.9, we can see that channel 4 has one zero LQA score days and

three low LQA score days. Moreover, it also has 4 medium score days from 21st

to

24th March. Channel 5 on the other hand has two zero LQA score days. It also has a



103

day with low score and three days of medium scores. The highest score of channel 4

is 14 which occurred on 21st; while for channel 5 is 15 which was on 17th. Thus

based on the results, it can be seen that channel 4 is better than channel 5 because it

has more low score days. Channel 4 is therefore the fourth best channel, while

channel 5 is the worst.

iii) Summary of Sounding during Timeslot 1

Based on the analysis of the LQA results of sounding made by Skudai and

Kota Bahru station, it can be seen that channel 2, which is 8.190 MHz and channel 1,

which is 8.002 MHz are the best channel to use during this timeslot. Channel 5,

which is 10.100 MHz must be avoided as this is the worst channel for this timeslot.

The summary of the results are shown in Table 6.6 below.

Table 6.6 Summary of LQA results for Skudai-Kota Bahru Circuit during timeslot 1

Sounding Station

Rank Skudai Kota Bahru

1 Channel 2 Channel 2






For each hour in this timeslot, Skudai, sounding occurred at 15 minutes past

every hour, which means on 3.15 p.m., 4.15 p.m., 4.15 p.m. Kota Bahru station on

the other hand performed sounding at every 30 minutes past the hour (at 3.30 p.m.,

4.30 p.m., 5.30 p.m.).



104


The LQA results for soundings from Skudai are shown Figure 6.11. Then on

Figure 6.12, the channel ranking is shown. Then the analysis from both LQA score

and channel ranking graphs are described in Table 6.7. From this table, and the

graphs in Figure 6.11 and 6.12, the best channel can be determined based on the

performance of each channel during this timeslot.

Figure 6.11 LQA result for Souding By Skudai during timeslot 2

0

5

10

15

20

25

30

35

40

45

50

03/17/2005 03/18/2005 03/19/2005 03/20/2005 03/21/2005 03/22/2005 03/23/2005 03/24/2005

Date

S c o r e




105

Figure 6.12 Channels Ranking for Sounding by Skudai during Timeslot 2

Table 6.7 Skudai-Kota Bahru Result Analysis for Sounding made by Skudai during

timeslot 2

LQA Score RankDays


1 4 2 1 0 1 4 1

2 7 1 0 0 0 4 0

3 3 3 2 0 0 0 3

4 4 2 2 0 0 0 2

5 2 5 0 0 1 0 2

Based on the results, it can be seen that channel 2 is the best channel because

throughout the 8 field-testing days, it has zero LQA scores almost everyday except

on 18th

where the score is 2. Then, based on channel ranking graph in Figure 6.11,

this channel was ranked as the best channel 4 times and was never ranked as the

worst channel.

0

1

2

3

4

5

6

03/17/2005 03/18/2005 03/19/2005 03/20/2005 03/21/2005 03/22/2005 03/23/2005 03/24/2005

Date

R a n k




106

According to Table 6. 7 and from the LQA score graph, it can be seen that

channel 1’s score is similar to channel 4. Both channels have four zero LQA score

days and two low score days. Channel 4 however has two medium score days and

has neither high nor very high LQA score day. Channel 1 on the other hand has one

medium LQA score day and one very high LQA score day, with the highest score of

43. Thus, channel 4 is determined as the second best channel and channel 1 is the

third best channel.

The fourth best channel is channel 5. this channel has two zero LQA score

days, five low score days and one very high score day. On the first four days, LQA

scores for this channel are in the range of 0 to 3. On the 21st

March however, the

score is 40, which is drastically higher. Then on the rest of three days, the score

became low again. Finally, the worst channel for this timeslot is channel 3. This

channel has three zero LQA score days, three low score days, and two medium LQA

score day. Although unlike channel 5, channel 3 does not very high LQA score, but

the overall performance of channel 5 is better than channel 3. This is because except

on 21st

March, channel 5’s LQA score is below 5. Moreover, by referring to channel

ranking graph in figure 6.12, it can be seen that channel 3 is ranked as the last

channel three times, the most times compared to other channels. Thus, channel 3 is

the worst channel.

ii) Sounding Made by Kota Bahru Station

Next on Figure 6.13, the LQA results for soundings made by Kota Bahru

station are presented. Following after that is Figure 6.14, which shows the channel

ranking based on LQA results for sounding made by Kota Bahru station. The

analysis of the results will follow after that in Table 6.8. Then comparison between

the results from sounding made by Kota Bahru station will follow after the table.



107

0

5

10

15

20

25

30

03/17/2005 03/18/2005 03/19/2005 03/20/2005 03/21/2005 03/22/2005 03/23/2005 03/24/2005

d a t e

S

c o r e


Figure 6.13 LQA result for sounding made by Kota Bahru during timeslot 2

Figure 6.14 Channels ranking for sounding by Kota Bahru during timeslot 2

0

1

2

3

4

5

6

03/17/2005 03/18/2005 03/19/2005 03/20/2005 03/21/2005 03/22/2005 03/23/2005 03/24/2005

Date

R a n k

channel 1: 8 .002MHz channel 2: 8 .190 MHz channel 3: 8 .710 MHz channel 4: 9 .108 MHz channel 5: 10.100 MHz



108


during timeslot 2

LQA Score RankDays


1 4 3 1 0 0 5 1

2 4 3 1 0 0 1 0

3 4 1 3 0 0 1 1

4 4 3 1 0 0 1 0

5 1 4 2 1 0 0 6

Based on the graphs illustrated in Figure 6.13, Figure 6.14 and Table 6.8,

overall, channel 4 is the best channel. This statement is made since the LQA score

for this channel is between 0 and 1 almost everyday, except on 17 March. On that

day, the score is 7, which is the highest score for this channel. Even though channel 4

is the best channel, but the difference between channel 4 and channel 2 is small.

Channel 2, similar to channel 4, always has low score, between 0 to 4 almost

everyday. The highest score for channel 2 occurred on the same day as channel 4,

and the value is the same, which is 7. The only difference between these two

channels is on the 18th and 23rd, where while channel 4 LQA score is 0 on both days,

the score for channel 2 is 4 and 2 respectively. Therefore, due to this, channel 2 is

determined as the second best channel. Then the third best channel is channel 1. Like

the first two channel, the score of this channel is also ranges from 0 to 5 almost

everyday except on 17th

March where the score is 7. However, channel 1 has slightly

higher LQA values from channel 4 and channel2. Channel 1 is therefore the third

best channel.

The fourth best channel is channel 3, which has four zero LQA score days,

one low LQA score day and three medium LQA score days. The highest score for

this channel 14, which occurred on 18th, and 19th

of March. This means that the

worst channel for sounding made by Kota Bahru during this timeslot is channel 5.

This is because channel 5 has only one zero LQA score day: the least compared to

the other four channels. It also has 4 low LQA score days, two medium score days



109

and one high LQA score day. The highest sore is 25, which occurred on 21 March.

Besides, according to the channel-ranking graph in Figure 6.14, this channel is

ranked as the worst channel six times, which is the most frequent among the other

four channels.


Based o the analysis above, we can see that for both stations in this timeslot,

the best channels to use is either channel 2: 8.190 MHz or channel 4: 9.108. Channel

1, which is 8.002 MHz, can also be used, but the performance is not as good as

channel 2 and channel 4. However, the other two channels, which are channel 3:

8.710 MHz and channel 5: 10.100 MHz, must not be used, as they are the worst

channels for this timeslot. Table 6.9 below shows the summary of the results.

Table 6.9 Summary of LQA Result for Skudai-Kota Bahru Result during Timeslot 2

Sounding Station

Rank Skudai Kota Bahru







For each hour in thi timeslots, both stations performed sounding once at

predetermined sounding time. For Skudai, sounding occurred at 15 minutes past

every hour, for example at 8.15 p.m and so on. Kota Bahru station on the other hand



110

performed sounding at every 30 minutes past the hour, for instance at 8.30 p.m. and

so on.

i) Sounding Made by Skudai Station

The graph illustrated in Figure 6.15 below shows the results of LQA based on

sounding made by Skudai station during timeslot 3. The soundings were conducted

for five days, beginning from 17th

March. Then on Figure 6.16, the ranking of each

channel on everyday are shown and after that, the analysis of the result is shown in

Table 6.10.

Figure 6.15 LQA result for sounding by Skudai During Timeslot 3

0

2

4

6

8

10

12

14

16

03/17/2005 03/18/2005 03/21/2005 03/23/2005 24/03/05

Date

S

c o

r e




111

Figure 6.16 Channels ranking for sounding by Skudai during timeslot 3

Table 6.10 Skudai-Kota Bahru Result Analysis for Sounding made by Skudai duringtimeslot 3.

LQA Score RankDays


1 1 1 3 0 0 2 1

2 1 1 3 0 0 1 0

3 1 2 2 0 0 2 0

4 0 0 5 0 0 0 1

5 0 0 5 0 0 0 3

According to the graph in Figure 6.15 and Table 6.10, it can be seen that the

best channel is channel 3. this is because this channel has the most number of days

with low LQA score. This channel has one zero LQA score day, two low LQA score

days and two medium LQA score days. The highest LQA score for this channel is 9

which occurred on 23rd

March. By referring to the channel-ranking graph in Figure

0

1

2

3

4

5

6

03/17/2005 03/18/2005 03/21/2005 03/23/2005 24/03/05

date

R

a n k

channel 1: 8 .002MHz channel 2: 8 .190 MHz channel 3: 8 .710 MHz channel 4: 9 .108 MHz channel 5: 10.100 MHz



112

6.16, it is clear that this channel is ranked as the best channel twice out of five field-

testing days.

LQA results for channel 1 and channel 2 are similar. Both channels has1 zero

LQA score day, two low LQA score days and three medium score days. The highest

LQA score for both channels occurred on 21st

March .The score for channel 2 on that

day is 9, while the score for channel 1 is 13. Thus, channel 2 is determined as the

second best channel followed by channel 1.

Channel 4 and channel 5 LQA scores are also similar. Both channels only

have medium LQA scores throughout the field-testing period. The highest score for

both channels are 15, which occured on 17th

, and 18th

March. The lowest score for

channel 4 is 8 which occurred on the 21st

March, while the lowest score for channel 5

is 7 which occurred on 24th

March. Thus, this means that channel 5 is the fourth best

channel and channel 4 is the worst channel.

ii) Sounding Made by Kota Bahru Station

The LQA results for sounding made by Kota Bahru station are illustrates by

the graph in Figure 6.17. Following that graph is channel-ranking graph in Figure

6.18. This graph shows the ranking of each channel during this timeslot everyday.

Then on Table 6.11 the analysis from LQA score graph in Figure 6.17 and channel

ranking graph in Figure 6.18 is shown. From this table, the best channel is

determined.



113

Figure 6.17 LQA results for sounding made by Kota Bahru during timeslot 3

Figure 6.18 Channels ranking for sounding by Kota Bahru during timeslot 3

0

5

10

15

20

25

30

35

03/16/2005 03/17/2005 03/18/2005 03/21/2005 03/22/2005 03/23/2005

Date

S

c o r e


0

1

2

3

4

5

6

03/16/2005 03/17/2005 03/18/2005 03/21/2005 03/22/2005 03/23/2005

date

R a n k

channel 1: 8.002MHz channel 2: 8.190 MHz channel 3: 8.710 MHz

channel 4: 9.108 MHz channel 5: 10.100 MHz



114


during timeslot 3.

LQA Score RankDays


1 2 3 1 0 0 4 0

2 3 3 0 0 0 2 0

3 1 2 2 0 1 0 0

4 0 1 4 1 0 0 0

5 0 1 4 0 1 0 6

Based on the graph in Figure 6.17 and Table 6.11, channel 2 is determined asthe best channel. This is because the number of zero LQA score days for this channel

is three, which is the highest among the five channels. The number of low LQA score

is also three. Moreover, this channel does not have any high LQA score and medium

score. Its highest score is 3 which occurred on 18th

March. The scores on most of the

days for this channel ranges from zero to 2. The next best channel, based on the

results, is channel 1. This channel also has no high LQA score, but it has one

medium score, which occurred on 23 March where the score is 6. Other than that,

channel 1 also has 2 zero LQA score days and 3 low score days.

The third best channel is based on the LQA results is channel 3. Overall, this

channel has one zero LQA score day and 2 low score days. Besides that, this channel

also has two medium LQA score days and one very high score day. The highest

score is 30, which occurred on 17 March. Then channel 4, which does not have any

zero LQA score day is considered as the fourth best channel. This channel has one

low LQA score day, four medium LQA score days and one high LQA score day.

Although the highest score for channel 4, which is 15, is not as high as channel 3’s,

this channel is still considered worse than channel 3. This is because channel 3 has

more low LQA score days than channel 4.



115

The worst channel according to the LQA results is channel 5. This channel

has no zero LQA score day, and only one low LQA score day. Moreover, it has four

medium LQA score days and one very high LQA score day. The highest score is 30,

which occurred on the 17th

. The lowest score is 3, which is on 18th

. By referring to

channel ranking graph in Figure 6.18, it can be seen that this channel is ranked as the

worst channel everyday.


From the analysis above, we can see that during timeslot 3, to communicate

between Kota Bahru and Skudai, using channel 2, which is 8.190 MHz is the best

way. A user can also use channel 3 which is 8.71 MHz or channel 1 which 8.002

MHz. The last two channels, which are 9.108 and 10.100 MHz, should be avoided

because these are the worst channels. Table 6.12 shows the summary of LQA results

for this timeslot.

Table 6.12 Summary of LQA Result for Skudai-Kota Bahru Circuit during Timeslot

3

Sounding StationRank

Skudai Kota Bahru








116

6.6.1.4 Comparisons Between Skudai-Kota Bahru Results and ASAPS

Prediction Results

The value of first mode Optimum Working Frequency (OWF1) according to

GRAFEX Frequency Prediction table shown in Figure 3.3 is 8.800 MHz during

timeslot 1, 9.900 MHz during timeslot 2 and 8.000 MHz during timeslot 3. On the

other hand, the value of first mode Absorption Limiting Frequency (ALF) for this

circuit is 3.6 MHz for timeslot 1, 3.2 MHz for timeslot 2 and finally zero for timeslot

3. Second mode OWF (OWF2) is 8.100 MHz for timeslot 1, 9.000 MHz during

timeslot 2 and 7.100 MHz during timeslot 3. The value of second mode ALF or

ALF2 are 3.2 MHz for timeslot 1, 2.8 MHz for timeslot 2, and zero for timeslot 3.

For sounding made by Skudai, the comparisons between the highest-ranked channels

for each timeslot and the predicted OWF are shown in Figure 6.19. Then on Figure

6.20 comparisons for sounding made by Kota Bahru is shown.

OWF1, 8.000

OWF1, 9.900

OWF1, 8.800

OWF2, 7.100

OWF2, 9.000

7.100

OWF2, 8.100

Channel 3:8.710

Channel 1: 8.002

Channel 2: 8.190

ALF1, 3.600

ALF1, 3.200

ALF2, 3.200ALF2, 2.800

ALF2, 0.0000.000

1.000

2.000

3.000

4.000

5.000

6.000

7.000

8.000

9.000

10.000

3 / 1 7 / 2 0 0 5

3 / 1 8 / 2 0 0 5

3 / 1 9 / 2 0 0 5

3 / 2 0 / 2 0 0 5

3 / 2 1 / 2 0 0 5

3 / 2 2 / 2 0 0 5

3 / 2 3 / 2 0 0 5

3 / 2 4 / 2 0 0 5

3 / 1 7 / 2 0 0 5

3 / 1 8 / 2 0 0 5

3 / 1 9 / 2 0 0 5

3 / 2 0 / 2 0 0 5

3 / 2 1 / 2 0 0 5

3 / 2 2 / 2 0 0 5

3 / 2 3 / 2 0 0 5

3 / 2 4 / 2 0 0 5

3 / 1 7 / 2 0 0 5

3 / 1 8 / 2 0 0 5

3 / 2 1 / 2 0 0 5

3 / 2 3 / 2 0 0 5

3 / 2 4 / 2 0 0 5

Timeslot 1 Timeslot 2 Timeslot 3

Date

F r e q u e n c y

( M

H z )

OWF1 OWF2 Skudai

ALF1 ALF2

Figure 6.19 Comparisons between highest-ranked channels and OWF values forSkudai-Kota Bahru circuit: sounding by Skudai



117

OWF1, 8.000

OWF1, 8.800

OWF1,9.900

OWF2, 7.100

OWF2, 9.000

OWF2, 8.100 Channel 3:8.710

Channel 4:9.108

Channel 2:8.190

Channel 1:8.002

ALF1, 3.600

ALF2, 3.200

0.000

1.000

2.000

3.000

4.000

5.000

6.000

7.000

8.000

9.000

10.000

3 / 1 7 / 2 0 0 5

3 / 1 8 / 2 0 0 5

3 / 1 9 / 2 0 0 5

3 / 2 0 / 2 0 0 5

3 / 2 1 / 2 0 0 5

3 / 2 2 / 2 0 0 5

3 / 2 3 / 2 0 0 5

3 / 2 4 / 2 0 0 5

3 / 1 7 / 2 0 0 5

3 / 1 8 / 2 0 0 5

3 / 1 9 / 2 0 0 5

3 / 2 0 / 2 0 0 5

3 / 2 1 / 2 0 0 5

3 / 2 2 / 2 0 0 5

3 / 2 3 / 2 0 0 5

3 / 2 4 / 2 0 0 5

3 / 1 7 / 2 0 0 5

3 / 1 8 / 2 0 0 5

3 / 2 1 / 2 0 0 5

3 / 2 2 / 2 0 0 5

3 / 2 3 / 2 0 0 5

Timeslot 1 Timeslot 2 Timeslot 3

Date

F r e q u e n c

( M

H

z )

OWF1 OWF2 Kota Bahru ALF1 ALF2

Figure 6.20 Comparisons between highest-ranked channels and OWF values

for Skudai-Kota Bahru circuit: sounding by Kota Bahru

Based on Figure 6.19 and Figure 6.20 above, it can be seen that for timeslot

1, the highest-ranking channels for both sounding by Skudai and Kota Bahru are

channel 1: 8.002 MHz and channel 2: 8.190 MHz. Both channel 1 and channel 2 are

located near the OWF2 and lower than OWF1. Channel 1 is located below both

OWF1 and OWF 2. Thus, this means that signals transmitted using this channel may

propagate either via first mode of second mode. Channel 2 on the other hand is above

OWF2, so there is a possibility that signals transmitted using this channel propagates

via the first propagation mode only.

For timeslot 2, OWF1 is 9.9 MHz, while OWF2 is 9.000 MHz. According to

Figure 6.19 for sounding made by Skudai, the top channels are channel 1 and

channel 2. Both channels are located below OWF 1 and OWF2 and higher than bothALF1 and ALF2, thus have 90% chances of success. For sounding made by Kota



118

Bahru, as shown in Figure 6.20, the highest-ranked channels are channel 1, channel

2, channel 3 (8.710 MHz) and channel 4 (9.200 MHz). Channel 1, channel 2 and

channel 3 are below OWF1 and OWF2, so all three frequencies have 90% chances

for success and may propagate via either first mode or second mode. On the other

hand, channel 4 is located above OWF2, thus propagates via first mode only.

During timeslot 3, OWF1 is 8.000 MHz while OWF2 is 7.100 MHz. The

highest-ranked channels during this timeslot for sounding made by Skudai are

channel 1 (8.002 MHz), channel 2 (8.190 MHz) and channel 3 which is 8.71. Then

by referring to Figure 6.20, the highest-ranked channels are only channel 1 and

channel 2. Channel 1 is located just above OWF1, thus have 90% chances to

succeed. However, both channel 2 and channel 3 is higher than OWF1 and OWF2.

These channels are still usable because they are below MUF. The MUF for this

timeslot according to the Field Strength Table in Figure 3.4 is 10.600 MHz.

Frequencies located between OWF and MUF has 50% to 90% chances to succeed.

6.6.2 Skudai-Chemor Results

Discussions in the following subsections are based on the LQA score graphs

and channel ranking graphs of the LQA results located in the database for both

timeslot 1 and timeslot 2. The full LQA results are shown in Appendix E.

6.6.2.1 Skudai-Chemor Sounding Results during Timeslot 1

Both stations performed sounding once at predetermined sounding time

during this timeslot. For Skudai, sounding occurred at 15 minutes past every hour,which means at 9.15 a.m., 10.15 a.m., 11.15 a.m. Chemor station on the other hand



119

performed sounding at every 30 minutes past the hour (at 9.30 a.m., 10.30 a.m. and

11.30 a.m).


The results for sounding made by Skudai station during timeslot 1 are

illustrated in the bar graph in Figure 6.21. This graph shows the LQA scores based

on sounding frame transmitted by Skudai station. Then the channel ranking result for

timeslot 1 is shown in line graph on Figure 6.22. Then from both graphs, analysis on

performance of each channel from 7th June 2005 to 21st June 2005 during timeslot 1

is done. For each channel, the scores are divided into the four LQA score categories

as shown in Table 6.3. The results of the analysis are shown in Table 6.13.

Figure 6.21 LQA result of sounding by Skudai during timeslot 1

0

5

10

15

20

25

30

35

40

0 6 / 0 7 / 2 0

0

0 6 / 0 8 / 2 0

0

0 6 / 0 9 / 2 0

0

0 6 / 1 0 / 2 0

0

0 6 / 1 3 / 2 0

0

0 6 / 1 4 / 2 0

0

0 6 / 1 5 / 2 0

0

0 6 / 1 7 / 2 0

0

0 6 / 2 0 / 2 0

0

0 6 / 2 1 / 2 0

0

Date

S c o r e

Channel 1: 8.190 MHz Channel 2: 7.100 MHz Channel 3: 8.710 MHz Channel 4: 8.002 MHz Channel 5: 9.200 MHz



120

Figure 6.22 Channel ranking for sounding by Skudai during timeslot 1

Table 6.13 Result analysis for Sounding made by Skudai during timeslot 1

LQA Score RankDays

ChannelZero Low Medium High Very high first last

1 0 1 3 1 5 1 1

2 2 2 2 4 0 7 1

3 0 1 1 1 7 0 1

4 0 1 0 3 6 1 4

5 0 2 2 3 3 1 3

From Table 6.13, it can be seen that channel 2 which is 7.100 MHz, is the

best channel for this timeslot. This is because channel 2 is the only channel that has

zero LQA score during the field-testing period. Zero LQA score occurred twice for

this channel which are on 17th

and 20th

June 2005. Besides that, this channel also has

two low LQA score days and three medium score days. This channel does not have

any very high scores (above 25). It does however have 4 high score days. Then,

according to Figure 6.22, it can be seen that this channel is usually ranked as the bestchannel. It was ranked the best channel on seven out of ten days of field-testing

0

1

2

3

4

5

6

06/07/2005 06/08/2005 06/09/2005 06/10/2005 06/13/2005 06/14/2005 06/15/2005 06/17/2005 06/20/2005 06/21/2005

Date

R a n k

Channel 1: 8.190 MHz Channel 2: 7.100 MHz Channel 3: 8.710 MHz

Channel 4: 8.002 MHz Channel 5: 9.200 MHz



121

period. Besides that, it was ranked as the worst channel only once which is on 9th

June. On the rest of the days, this channel is ranked as the third best channel.

The second best channel, according to Figure 6.21 and Figure 6.22 would

have to be channel 5 which is 9.200 MHz. Low LQA score occurred twice for this

channel, which are on 14th

and 17th

June. Besides that, this channel also has two

medium LQA score days, which means that the score is between 6 to 15. However,

this channel has three very high LQA score days, with the highest score of 32. Other

than that, it also has high LQA score days on three out of ten days. Then by looking

at Figure 6.22, it can be seen that this channel is ranked as the best channel once, and

ranked three times as the worst channel. However, during the field-testing, it is

ranked most of the days as the second best channel. Following after that is channel 1,

which is 8.19 MHz. This channel is chosen as the third best channel because by

referring to Table 6.13 and Figure 6.21, channel 1 has one low LQA score day,

which is on 10th

June with the score of 3. Then medium LQA score for this channel

occurred on three days and this channel only has one high score day which is on 7th

June. For the rest of the field-testing period, the scores are very high.

Channel 4 which is 8.002 MHz has only one low LQA score day and neither

zero nor medium LQA score day. This channel has one low LQA score day, on 9th

of

June with the score of 1. This is the lowest LQA score for this channel. On three days

out of the field-testing period, this channel has high LQA score which is between 16

to 25. This channel has 6 very high score days which makes this channel not good for

communication. Similarly, channel 3 which is 8.710 MHz also has no zero LQA

score day and one low LQA score day. Channel 3 however, has 1 medium LQA

score day and 1 high LQA score day. The lowest score for this channel is 3 which

occurs on 9th

June. Channel 3 has the most number of very high LQA score days

which is 7. therefore, after considering the results it can be said that channel 4 is the

fourth best channel and channel 3 is the worst channel during timeslot 1.



122

ii) Sounding Made by Chemor Station

Next on discussion is the results for sounding made by Chemor station during

timeslot 1. The LQA score results are illustrated in the bar graph in Figure 6.23.

Then the channel ranking result is shown in line graph on Figure 6.24. The analysis

of both graphs in Figure 6.23 and Figure 6.24 are shown in Table 6.14. From this

table, performance of each channel is compared and after that, the best channel is

determined.

Figure 6.23 LQA result of sounding by Chemor during Timeslot 1

0

5

10

15

20

25

30

35

40

0 6 / 0 7 /

2 0 0 5

0 6 / 0 8 / 2 0

0 5

0 6 / 0 9 / 2 0

0 5

0 6 / 1 0 / 2 0

0 5

0 6 / 1 3 / 2 0

0 5

0 6 / 1 4 / 2 0

0 5

0 6 / 1 5 / 2 0

0 5

0 6 / 1 7 /

2 0 0 5

0 6 / 2 0 / 2 0

0 5

0 6 / 2 1 / 2 0

0 5

Date

S

c o r e





123

Figure 6.24 Channel ranking for sounding by Chemor during timeslot 1

Table 6.14 Result analysis for Sounding made by Chemor during timeslot 1

LQA Score Rank Days

Channel

Zero Low Medium High Very high First Last

1 0 0 4 2 4 1 1

2 1 1 5 2 1 8 0

3 0 0 1 2 7 0 1

4 0 0 1 2 7 0 3

5 0 0 1 5 4 1 5

Based on Figure 6.23, Figure 6.24 and Table 6.14, it can be seen that channel

2 is the best channel. This is because this is the only channel that has zero and low

LQA score days. Zero score occurred on the 20th

June while low LQA score occurred

on 17th

June. There are five days with medium LQA score and two days with high

LQA score. Finally, this channel has only one very high LQA score day which is on

7th June. Then by referring to the channel ranking graph, it can be seen that this

channel is ranked as the best channel on 8 days and has never been ranked as the last

channel.

0

1

2

3

4

5

6

0 6 / 0 7 /

2 0 0 5

0 6 / 0 8 / 2 0

0 5

0 6 / 0 9 / 2 0

0 5

0 6 / 1 0 / 2 0

0 5

0 6 / 1 3 / 2 0

0 5

0 6 / 1 4 / 2 0

0 5

0 6 / 1 5 / 2 0

0 5

0 6 / 1 7 /

2 0 0 5

0 6 / 2 0 / 2 0

0 5

0 6 / 2 1 / 2 0

0 5

Date

R

a n k





124

The second best channel, based on the results is channel 1 which has neither

zero nor low LQA score day. According to the results, this channel has four medium

LQA score days. Other than that, this channel has two high and very four high LQA

score days. Based on channel ranking graph in Figure 6.24, channel 1 is ranked as

the best and the last channel once. It is usually ranked as the second best channel.

The discussion now move on to channel 5 which is ranked as the third best channel.

Same as channel 1, this channel does not have any zero and low LQA score day.

Nonetheless, channel 5 has one medium LQA score day, five high LQA score days

and four very high LQA score days.

The performance of channel 3 and channel 4 are similar to each other. The

results shows that both channels have one medium LQA score day, two high LQA

score days and 7 very high LQA score days. However, the highest LQA score for

channel 4 is 37 while the highest score for channel 3 is 30. Therefore, channel 3 is

ranked as the fourth best channel and channel 4 is the worst channel.


Table 6.15 shows the summary of LQA result for this timeslot. Based on

analysis, the best channel for timeslot 1 is channel 2, which is 7.100 MHz. Thus,

compared to the other five channels, channel 2 is the most suitable frequency to use

for communication. Other than that, channel 1, which is 8.190 MHz and channel 5

which is 9.200 MHz can also be used for communication.



125

Table 6.15 Summary of LQA Results for Skudai-Chemor Circuit during Timeslot 1


Skudai Chemor






6.6.2.2 Skudai-Chemor Sounding Results during Timeslot 2

For Skudai, sounding during this timeslot is done at 15 minutes past every

hour, for example at 2.15 p.m and so on. Chemor station on the other hand performed

sounding at every 30 minutes past the hour for example at 2.30 p.m. and so on.

i) Sounding Made by Skudai Station

Sounding by Skudai is done hourly at every 15 minutes past the hour. For

timeslot 2, data is collected at 2.15 p.m. and 3.15 p.m. everyday from 8th June until

21st

June 2005. The LQA score for these sounding are illustrated in Figure 6.25.

Then on figure 6.26, the channel-ranking graph is shown. Analysis of the results for

each channel is done by dividing the days by according to the LQA score categories.

The results of the analysis are shown in Table 6.16.



126

Figure 6.25 LQA result of sounding by Skudai during timeslot 2

Figure 6.26 Channel ranking for sounding by Skudai during timeslot 2

0

1

2

3

4

5

6

06/08/2005 06/09/2005 06/10/2005 06/14/2005 06/15/2005 06/16/2005 06/20/2005 06/21/2005

Date

R a n k



0

5

10

15

20

25

30

35

40

45

50

06/08/2005 06/09/2005 06/10/2005 06/14/2005 06/15/2005 06/16/2005 06/17/2005 06/20/2005 06/21/2005

Date

S c o r e




127

Table 6.16 Result analysis for Sounding Made by Skudai during Timeslot 2

LQA Score Rank

Days

Channel

Zero Low Medium

High Very high First Last

1 0 0 1 4 4 1 2

2 2 2 2 1 2 4 1

3 2 0 0 2 5 1 1

4 0 2 0 2 5 0 3

5 3 1 0 2 3 3 2

Based on the LQA score graph in Figure 6.25 and Table 6.16, it can be seen

that channel 2 which is 7.100 MHz is the best channel. This channel has two zero,

low and medium LQA score days. It has only one high LQA score day and two days

with very high LQA score days. Channel 5 which is 9.200 MHz has 3 zero LQA

score days, the highest among the five channels. It also has 1 low score days and no

medium LQA score day. This channel also has two high LQA score days and three

very high LQA score days. The reason why channel 2 is selected as the best channel

instead of channel 5 is that by referring to Table 6.16 and Figure 6.26, it can be seen

that channel 2 is ranked as the best channel for four times, while channel 5 is ranked

three times. More over, overall, channel 5 has more number of high LQA score days

than channel 2.

The third best channel according to the results is channel 3 which is 8.710

MHz. this channel has 2 zero LQA score days which occurred on 10th

and 20th

June.

However, this channel does not have any low and medium LQA score days. It has

two high LQA score days and very high LQA score on the rest for five days. based

on Figure 6.25, this channel has only been ranked as the best channel once.

To determine which is the fourth best channel and the worst channel,

comparison is done between channel 1 which is 8.190 MHz and channel 4 which is

8.002 MHz. From the LQA score graph, it can be seen that both channels do not have

any zero LQA score days. For low LQA score, channel 1 does not have any while



128

channel 4 has two days with low LQA score. However, channel 1 has a day with

medium score, but channel 4 does not. Next, channel 1 has 4 high and very high

LQA score days. Channel 4 on the other hand has 2 high score days and five very

high score days. Thus from the result, channel 4 is clearly is better than channel 1

because it has more lower score days than channel 1. Therefore, channel 4 is the

fourth best channel and channel 1 is the worst channel for timeslot 2.

iv) Sounding Made by Chemor Station

The LQA score results for sounding made by Chemor station during timeslot

2 are illustrated in the bar graph in Figure 6.27. Then the channel ranking result is

shown in line graph on Figure 6.28. The analysis of both graphs in Figure 6.27 and

Figure 2.28 are shown in Table 6.17. From this table, performance of each channel is

compared and the best channel is determined.

Figure 6.27 LQA result of sounding by Chemor during timeslot 2

0

5

10

15

20

25

30

35

40

0 6 / 0 8 / 2 0

0

0 6 / 0 9 / 2 0

0

0 6 / 1 0 / 2 0

0

0 6 / 1 4 / 2 0

0

0 6 / 1 5 / 2 0

0

0 6 / 1 6 / 2 0

0

0 6 / 1 7 /

2 0 0

0 6 / 2 0 / 2 0

0

0 6 / 2 1 / 2 0

0

Date

S

c o r e





129

Figure 6.28 Channel ranking for sounding by Chemor during timeslot 2

Table 6.17 Result analysis for Sounding made by Chemor during timeslot 2

LQA Score Rank

Days

Channel

Zero Low Medium High Very high First Last

1 0 0 1 1 7 0 4

2 2 2 2 1 2 6 1

3 1 0 0 2 6 1 0

4 0 1 0 2 6 0 2

5 2 0 1 2 4 2 2

The best channel, according to results in Figure 2.27 and also Table 6.17 is

channel 2. This is due to the fact that this channel has two zero and low LQA score

days. Besides that, it also has two medium score days and only one high score day.

The number of days with very high score are also low, which is 2. Channel 2 is also

mostly ranked as the best channel according to the channel-ranking graph in Figure

6.28. Throughout the field-testing period, it is ranked as the best channel for six

times, the highest among the rest of the channels. The second best channel is channel

5, which also has 2 zero LQA score days. However, this channel does not have any

0

1

2

3

4

5

6

06/08/2005 06/09/2005 06/10/2005 06/14/2005 06/15/2005 06/16/2005 06/17/2005 06/20/2005 06/21/2005

Date

R a n k




130

low LQA score day and only one day with medium LQA score. It then has two high

LQA score days and four very high LQA score days. For channel ranking, channel 5

is ranked as the best channel twice.

Following channel 5 is channel 3. This channel is chosen as the third best

channel because it has only one zero LQA score day. Other than that, this channel

has no low and no medium LQA score day. It has 2 high LQA score days and 6 very

high LQA score days. This channel has only been ranked as the best channel once

and never ranked as the worst channel. Figure 6.27 shows that the performance of

channel 3 is almost the same as channel 4 except that channel instead of having a

zero LQA score day, channel 4 has one low LQA score day. The number of high and

very high LQA score days for both channels are the sane. Channel 4 has never been

ranked as the best channel and ranked twice as the worst channel. Therefore based on

the results, channel 4 is determined as the fourth best channel. The worst channel for

this timeslot is channel 1. This channel has neither zero nor low LQA score day. It

has one medium and high score day, and 7 very high LQA score days: the highest

among the five channels. By referring to the channel ranking graph in Figure 6.28, it

can be seen that this channel has the highest number of times ranked as the worst

channel compared to the other channels.


According to LQA results from sounding made by both station, the most

suitable frequencies to be used are channel 2 which is 7.100 MHz. Then the second

best channel to use is channel 5 which is 9.200 MHz. Channel 3, which is 8.71 MHz,

can also be used. Nevertheless, the performance of this channel is not as good as both

channel 2 and channel 5. Channel 1, which is 8.19 MHz must be avoided during this

timeslot. This is because according to the LQA results, this is the worst channel. The

summary of the results are shown in Table 6.18 below.



131

Table 6.18 Summary of LQA results for Skudai-Chemor Circuit during Timeslot 2


Skudai Chemor






6.6.2.3 Comparisons Between Skudai-Chemor Results and ASAPS Prediction

Results

On Figure 6.29, comparison between highest-ranked channel everyday and

OWF for sounding made by Skudai is shown. Then on Figure 6.30, the comparison

for sounding made by Chemor station is shown. The OWF value for this circuit

during timeslot 1 is 8.600 MHz, while for timeslot 2 is 8.300 MHz. The ALF for

timeslot 1 is 3.4 MHz, while for timeslot 2, the ALF value is 3.5 MHz. The OWF

and ALF are obtained from GRAFEX Frequency Prediction table shown in Figure

3.5



132

OWF, 8.600OWF, 8.300

Channel 4: 8.002

Channel 2: 7.100

Channel 1: 8.190

Channel 5: 9.200

Channel 3: 8.710

ALF, 3.500ALF, 3.400

2.000

3.000

4.000

5.000

6.000

7.000

8.000

9.000

10.000

6 / 7 /

2 0 0 5

6 / 8 /

2 0 0 5

6 / 9 /

2 0 0 5

6 / 1 0 /

2 0 0 5

6 / 1 3 /

2 0 0 5

6 / 1 4 /

2 0 0 5

6 / 1 5 /

2 0 0 5

6 / 1 7 /

2 0 0 5

6 / 2 0 /

2 0 0 5

6 / 2 1 /

2 0 0 5

6 / 8 /

2 0 0 5

6 / 9 /

2 0 0 5

6 / 1 0 /

2 0 0 5

6 / 1 4 /

2 0 0 5

6 / 1 5 /

2 0 0 5

6 / 1 6 /

2 0 0 5

6 / 2 0 /

2 0 0 5

6 / 2 1 /

2 0 0 5

Timeslot 1 Timeslot 2Date

F r e q u e n c y ( M H z )

OWF Skudai ALF

Figure 6.29 Comparisons between highest-ranked channels and OWF for Skudai-

Chemor Circuit: sounding by Skudai

OWF, 8.600

OWF, 8.300

Channel 5: 9.200

Channel 2: 7.100

Channel 1: 8.190

Channel 3: 8.710

ALF, 3.500ALF, 3.400

2.000

3.000

4.000

5.000

6.000

7.000

8.000

9.000

10.000

6 / 7 / 2 0 0 5

6 / 8 / 2 0 0 5

6 / 9 / 2 0 0 5

6 / 1 0 / 2 0 0 5

6 / 1 3 / 2 0 0 5

6 / 1 4 / 2 0 0 5

6 / 1 5 / 2 0 0 5

6 / 1 7 / 2 0 0 5

6 / 2 0 / 2 0 0 5

6 / 2 1 / 2 0 0 5

6 / 8 / 2 0 0 5

6 / 9 / 2 0 0 5

6 / 1 0 / 2 0 0 5

6 / 1 4 / 2 0 0 5

6 / 1 5 / 2 0 0 5

6 / 1 6 / 2 0 0 5

6 / 2 0 / 2 0 0 5

6 / 2 1 / 2 0 0 5

Timeslot 1 Timeslot 2

Date

F r e q u e n c y ( M H z )

OWF Chemor ALF

Figure 6.30 Comparisons between highest-ranked channels and OWF for Skudai-

Chemor circuit: sounding by Chemor



133

Based on Figure 6.29, it can be seen that all channels became the highest-

ranked channel at least once throughout the field-testing period. For timeslot 1, it can

be seen that most of the highest-ranked channels (channel 1: 8.190 MHz, channel 2:

7.100 MHz and channel 4: 8.002 MHz) are located below the OWF and higher than

ALF. Frequencies within this range have 90% chances to succeed. Only channel 3,

which is 8.71, and channel 5, which is 9.200 MHz, are higher than OWF. However,

both channel 3 and channel 5 are lower than MUF for this timeslot, which according

to Field Strength Table in Figure 3.6 is 10.200 MHz. The same condition can be seen

for timeslot 2, where the OWF is 8.300 MHz and the MUF is 10 MHz. Overall, for

both timeslots, channel 2 which is the best channel for is located below OWF. The

second best channel, which is channel 5 however is located above OWF for this

timeslot but lower than MUF.

Then Figure 6.30 shows that during timeslot 1, for sounding made by Chemor,

most highest-ranked channel that is channel 2 is below OWF and higher than ALF.

Another highest-ranked channel, which is channel 1 is also located below OWF.

Only channel 5, which was ranked as the best channel once is located above OWF.

The same results can be seen for timeslot 2 where the OWF is 8.300 MHz. Channel 1

is located below OWF, while channel 5 is above OWF. Other than that, for this

timeslot, channel 3 is ranked as the best channel once. The location of channel 3 is

above OWF.

6.7 Summary

For Skudai-Kota Bahru circuit, from the five channels used, it is clear that in

the morning, the best frequency was 8.190 MHz. In the afternoon, two frequencies

can be used, which are 8.190 MHz and 9.108 MHz. Then at nighttime, both 8.71

MHz and 8.190 MHz were suitable to use for communication. Thus, overall, it canbe seen that 8.190 MHz was usable throughout the field-testing period. For Skudai-



134

Chemor circuit, field-testing were only conducted in the morning and afternoon.

During morning, the most suitable frequency to use was 7.100 MHz. The same

frequency was also usable in the afternoon. Other than that, 9.200 MHz can also be

used in the afternoon.

Comparisons are then made between the results obtained and results from

ASAPS frequency prediction. By doing this, the differences between real-time and

predicted results can be seen. Based on the field-testing results, generally, channels

located between the ALF and OWF have 90% of chances to succeed. However, due

to other factors such as noise, attenuation and interferences, some of these

frequencies are less usable. Results from the comparison shows that the system is

able to select the most suitable channel to use for communication because most of

the results from field-testing agree with the predicted results.



CHAPTER VII

CONCLUSIONS AND RECOMMENDATIONS

7.1 Conclusions

HF spectrum which ranges from 3 to 30 MHz is reflected by the ionosphere.

Thus the availability of each frequency in this band relies closely to the condition of

the ionosphere. Other than that, factors such as noise, interference and propagation

problems also affect the availability of frequencies in HF spectrum. The availability

of frequencies also varies with location, time, days and season. Hence, selecting the

best frequency is fundamental to ensure reliable communication. Automatic link

establishment or ALE is sets of protocols that can be use to solve this problem. ALE

performs real-time channel evaluation through its sounding and link quality analysis

(LQA) protocols to find the best frequency to be used at specific time and location.

Without the help of ALE, a user has to manually listen on each preselected

frequencies, to look for clear, unoccupied frequencies to use. Other than that, if

frequency prediction software is used, the predicted best usable frequency may not

be usable due to real-time interference such as noise.

The system designed in this research is a messaging system which permitspoint to point communication between two remote stations using the best frequency



136

available. This system has ALE capability that handles the processes of selecting the

best frequency and linking to another station. Implementing ALE in form of software

is very cost effective and convenient for users as no extra equipment is needed. Other

than that, this system uses low power to transmit data. The transmit power used in all

field-testing is between 10 to 20 Watts.

The results obtained from field-testing in this research verify that the most

important feature in an ALE system is that its ability to select the best possible

channel to use at any time of day. This is achieved by performing sounding and LQA

at every hour. Sounding and LQA featured in this system is a form of real-time

channel evaluation that gives actual and immediate results of channels condition.

Results from any frequency prediction software on the other hand are predicted

results from calculation based on empirical data. From the field-testing results, it can

be seen that both results do not differ very much from each other. This is because

most of the best usable frequencies obtained from the field testing are between the

range of Optimum Working Frequency (OWF) and Absorption Limiting Frequency

(ALF) which according to the prediction has 90% chances of success.

7.2 Recommendations For Future Works

To improve the performance of the system designed in this research, some

improvements and modifications can be done. Thus, recommendations for future

work of this research are as below

i) Instead of having only a point to point connection between two stations, this

system can be expanded by increasing the number of stations that can be

connected. Stations can be connected to each other either by using point to

point connection or by network connection.



137

ii) Other ALE features such as orderwire message capability and multi stations

application can also be added to the system.

iii) To upgrade the efficiency of this system, the predicted results from

propagation prediction programs such as ASAPS should be uploaded

automatically by the system. The system can also be made able to select

which frequencies to be used automatically based on the results from

propagation prediction software. Frequency selection should be based on

predicted OWF, MUF, ALF and also the SNR of the possibly usable

frequencies.

iv) The field-testing sites selected in this research are both located in peninsular

Malaysia. For future work, the field-testing sites can be expanded to location

outside peninsular Malaysia. Other than that, field-testing can also be done

between land and sea (on ship).

v) Finally, this system can also be upgraded to make it available to use with

other type of HF radio and modem.



138

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McGraw-Hill.



APPENDIX A

ASAPS PREDICTION RESULTS



144

Figure A.1: Frequency Plan Table for Skudai-Kota Bahru Circuit

===============================================================================

ASAPS V5 FREQUENCY PLAN PREDICTIONS ---------------------------- 21 Mar 2005

===============================================================================

Circuit 1: skudai-kota bahru Distance: 535km Date: March 2005

Tx: skudai 1 33.6 103 39. Bear: 6116 2898 Mils T-index: 30

Rx: kota bahru 6 10.2 102 16. Path: Short Path

Selected frequency set: utm

3.853 3.959 6.650 6.702 7.080 7.100 7.686 8.002 8.113 8.1908.710 9.108 9.460 10.100 10.900 14.365 14.773

===============================================================================

Mode: 1F TakeOff Angle:40-59 | Mode: 1E TakeOff Angle:17

Probability > 90% | Probability 50-90% |

===============================================================================

Time Frequency | Time Frequency | Time Frequency

UT MHz | UT MHz | UT MHz

0000-0100 6.650 | 0000-0100 7.686 | 0000-0200 3.959

0100-0200 8.190 | 0100-0200 9.460 | 0200-0300 6.702

0200-0700 8.710 | 0200-0500 10.100 | 0300-0400 7.100

0700-0800 9.108 | 0500-0600 9.460 | 0400-0700 7.686

0800-1000 9.460 | 0600-0800 10.100 | 0700-0800 7.100

1000-1100 10.100 | 0800-1400 10.900 | 0800-0900 7.080

1100-1200 9.108 | 1400-1700 10.100 | 0900-1100 3.959

1200-1400 8.190 | 1700-1800 8.710 | 1100-2400 None

1400-1700 7.686 | 1800-1900 7.686 |

1700-1800 6.702 | 1900-2000 None |

1800-2000 3.959 | 2000-2400 3.959 |

2000-2400 None | |

===============================================================================

Mode: 2F TakeOff Angle:60-73 | Mode: 2E TakeOff Angle:33

Probability > 90% | Probability 50-90% |

===============================================================================

Time Frequency | Time Frequency | Time Frequency

UT MHz | UT MHz | UT MHz

0000-0100 3.959 | 0000-0100 6.702 | 0000-0100 None

0100-0200 7.100 | 0100-0200 8.190 | 0100-0200 3.853

0200-0500 8.002 | 0200-0400 9.108 | 0200-1000 3.959

0500-0600 7.686 | 0400-0700 8.710 | 1000-2400 None

0600-0700 8.002 | 0700-0900 9.460 |

0700-0900 8.190 | 0900-1300 10.100 |

0900-1000 8.710 | 1300-1400 9.460 |

1000-1100 9.108 | 1400-1500 9.108 |1100-1200 8.190 | 1500-1700 8.710 |

1200-1300 7.686 | 1700-1800 7.686 |

1300-1400 7.100 | 1800-1900 6.650 |

1400-1500 7.080 | 1900-2000 None |

1500-1700 6.702 | 2000-2200 3.959 |

1700-2000 3.959 | 2200-2300 None |

2000-2400 None | 2300-2400 3.959 |

===============================================================================



145

Figure A.2: Frequency Plan Graph for Skudai-Kota Bahru Circuit

Figure A.3:GRAFEX Graph for Skudai-Kota Bahru Circuit



146

Figure A.4: Frequency Plan Table for Skudai-Chemor Circuit

Figure A.5: Frequency Plan Graph for Skudai-Chemor Circuit



147

Figure A.6: GRAFEX Prediction Graph for Skudai-Chemor Circuit



148

APPENDIX B

KENWOOD TS570D TRANSCEIVER SPECIFICATIONS



149



150

APPENDIX C

KANTRONICS KAM ’98 MODEM SPECIFICATIONS



151



152



153

APPENDIX D

EXPERIMENTAL LICENSE FOR HF



154

Figure D.1 Experimental License First Page



155

Figure D.2 Experimental License Second Page



APPENDIX E

LQA RESULTS FOR SKUDAI-KOTA BAHRU FIELD-TESTING



157

Table E1. LQA Results for Sounding Made by Skudai

LQA Score Rank

sound_date time timeslot ch1 ch2 ch3 ch4 ch5 ch1 ch2 ch3 ch4 ch5 station

03/11/2005 9 1 2 2 10 0 11 2 3 4 1 5 003/21/2005 9 1 15 15 15 15 15 1 2 3 4 5 1

03/21/2005 9 1 7 7 7 7 15 1 2 3 4 5 1

03/11/2005 10 1 11 0 0 2 22 4 1 2 3 5 0

03/11/2005 10 1 11 0 13 2 13 3 1 4 2 5 1

03/18/2005 10 1 0 15 15 15 15 1 2 3 4 5 0

03/18/2005 10 1 0 3 3 3 15 1 2 3 4 5 0

03/19/2005 10 1 0 0 7 3 15 1 2 4 3 5 0

03/20/2005 10 1 0 0 0 0 0 1 2 3 4 5 1

03/24/2005 10 1 0 2 7 7 7 1 2 3 4 5 0

03/17/2005 10 1 0 0 15 0 1 1 2 5 3 4 0

03/18/2005 11 1 0 3 3 4 3 1 2 3 5 4 0

03/19/2005 11 1 15 0 41 1 4 4 1 5 2 3 0

03/20/2005 11 1 0 0 0 0 0 1 2 3 4 5 0

03/22/2005 10 1 2 0 7 7 7 2 1 3 4 5 0

03/23/2005 11 1 7 7 7 7 7 1 2 3 4 5 0

03/24/2005 11 1 3 4 5 5 9 1 2 3 4 5 0

03/19/2005 12 2 4 0 14 0 1 4 1 5 2 3 1

03/20/2005 12 2 0 0 3 15 15 1 2 3 4 5 0

03/21/2005 12 2 2 0 0 3 15 3 1 2 4 5 0

03/23/2005 12 2 0 7 9 9 9 1 2 3 4 5 0

03/24/2005 12 2 9 9 9 9 9 1 2 3 4 5 0

03/17/2005 15 2 7 7 7 7 15 1 2 3 4 5 1

03/18/2005 15 2 0 0 3 0 0 1 2 5 3 4 0

03/19/2005 15 2 0 0 15 0 0 1 2 5 3 4 0

03/20/2005 15 2 1 4 4 11 1 1 3 4 5 2 0

03/21/2005 15 2 0 0 0 0 15 1 2 3 4 5 1

03/22/2005 15 2 0 0 7 7 7 1 2 3 4 5 0

03/23/2005 15 2 0 0 0 0 2 1 2 3 4 5 0

03/24/2005 15 2 0 0 0 0 7 1 2 3 4 5 0

03/18/2005 16 2 0 0 4 15 15 1 2 3 4 5 0

03/19/2005 16 2 0 0 5 0 0 1 2 5 3 4 0

03/20/2005 16 2 1 1 15 5 0 2 3 5 4 1 0

03/21/2005 16 2 0 0 1 0 4 1 2 4 3 5 1

03/18/2005 17 2 15 2 4 15 3 4 1 3 5 2 0

03/19/2005 17 2 0 0 15 0 15 1 2 4 3 5 0

03/20/2005 17 2 1 0 8 1 0 3 1 5 4 2 0

03/21/2005 17 2 43 0 0 0 40 5 1 2 3 4 0

03/22/2005 16 2 0 0 1 1 3 1 2 3 4 5 0

03/23/2005 16 2 2 0 0 7 1 4 1 2 5 3 0

03/24/2005 16 2 0 0 0 0 4 1 2 3 4 5 0

03/21/2005 20 3 1 0 0 4 16 3 1 2 4 5 1

03/22/2005 20 3 1 1 1 1 7 1 2 3 4 5 0

03/23/2005 20 3 0 0 0 2 7 1 2 3 4 5 0



158

sound_date time timeslot

LQA

Score Rank 0 0 1 2 3 4 5 0

ch1 ch2 ch3 ch4 ch5 ch1 ch2 ch3 ch4 ch5 station

03/21/2005 21 3 6 15 15 15 15 1 2 3 4 5 1

03/22/2005 21 3 5 7 9 9 9 1 2 3 4 5 0

03/23/2005 21 3 7 3 6 8 9 3 1 2 4 5 003/23/2005 21 3 1 1 1 2 9 1 2 3 4 5 0

03/23/2005 21 3 7 7 7 8 9 1 2 3 4 5 0

03/16/2005 22 3 2 0 30 30 30 2 1 3 4 5 0

03/17/2005 22 3 0 0 0 15 15 1 2 3 4 5 0

03/18/2005 22 3 15 6 6 15 15 3 1 2 4 5 0

03/21/2005 21 3 13 9 7 8 10 5 3 1 2 4 0

03/22/2005 21 3 5 7 9 9 9 1 2 3 4 5 0

03/23/2005 22 3 9 8 9 9 9 2 1 3 4 5 0



159

Table E2. LQA Results for Sounding Made by Kota Bahru

LQA Score Rank


03/18/2005 10 1 15 3 1 15 0 4 3 2 5 1 103/19/2005 10 1 0 0 0 3 0 1 2 3 5 4 0

03/19/2005 10 1 0 0 0 15 15 1 2 3 4 5 1

03/20/2005 10 1 0 0 0 0 0 1 2 3 4 5 0

03/22/2005 10 1 7 2 7 7 7 2 1 3 4 5 0

03/24/2005 10 1 0 0 7 7 7 1 2 3 4 5 0

03/24/2005 10 1 0 0 15 15 15 1 2 3 4 5 1

03/17/2005 11 1 0 0 15 1 15 1 2 4 3 5 0

03/18/2005 11 1 3 0 0 3 0 4 1 2 5 3 0

03/19/2005 11 1 3 0 0 4 4 3 1 2 4 5 0

03/21/2005 11 1 0 0 0 14 7 1 2 3 5 4 0

03/24/2005 11 1 1 7 11 11 11 1 2 3 4 5 0

03/17/2005 10 2 0 0 15 0 1 1 2 5 3 4 1

03/19/2005 12 2 4 1 16 1 1 4 1 5 2 3 0

03/20/2005 12 2 0 0 15 15 15 1 2 3 4 5 0

03/21/2005 12 2 0 0 0 7 9 1 2 3 4 5 0

03/23/2005 12 2 30 0 7 7 7 1 2 3 4 5 0

03/18/2005 15 2 0 0 3 0 0 1 2 5 3 4 0

03/19/2005 15 2 0 0 15 0 0 1 2 5 3 4 1

03/20/2005 15 2 0 0 0 0 0 1 2 3 4 5 0

03/22/2005 15 2 0 0 0 0 0 1 2 3 4 5 0

03/22/2005 15 2 0 0 0 0 1 1 2 3 4 5 1

03/23/2005 15 2 0 0 0 0 2 1 2 3 4 5 1

03/24/2005 15 2 0 0 0 0 7 1 2 3 4 5 0

03/18/2005 16 2 3 4 14 0 15 2 3 4 1 5 0

03/19/2005 16 2 0 0 5 0 0 1 2 5 3 4 1

03/20/2005 16 2 0 0 0 0 0 1 2 3 4 5 0

03/21/2005 16 2 0 0 1 0 4 1 2 4 3 5 0

03/22/2005 16 2 0 0 0 1 1 1 2 3 4 5 0

03/23/2005 16 2 5 2 0 0 0 5 4 1 2 3 0

03/24/2005 16 2 0 0 0 1 3 1 2 3 4 5 0

03/18/2005 17 2 15 2 4 15 3 4 1 3 5 2 1

03/20/2005 17 2 0 0 2 1 3 1 2 4 3 5 0

03/21/2005 17 2 0 4 1 0 8 1 4 3 2 5 0

03/21/2005 17 2 0 1 0 0 25 1 4 2 3 5 0

03/21/2005 20 3 1 0 0 4 16 3 1 2 4 5 0

03/22/2005 20 3 7 7 7 7 7 1 2 3 4 5 0



160

LQA Score Rank


03/22/2005 20 3 7 7 7 7 7 1 2 3 4 5 0

03/23/2005 20 3 0 0 2 7 7 1 2 3 4 5 0

03/23/2005 20 3 7 7 7 7 7 1 2 3 4 5 0

03/21/2005 21 3 0 0 7 8 11 1 2 3 4 5 0

03/22/2005 21 3 6 1 6 6 11 2 1 3 4 5 0

03/23/2005 21 3 2 2 2 9 9 1 2 3 4 5 0

03/18/2005 22 3 3 3 3 3 3 1 2 3 4 5 0

03/23/2005 22 3 4 6 18 9 9 1 2 5 3 4 0

03/23/2005 22 3 9 8 5 10 7 4 3 1 5 2 1

03/16/2005 23 3 2 0 30 19 30 2 1 4 3 5 0



APPENDIX F

LQA RESULTS FOR SKUDAI-CHEMOR FIELD-TESTING



162

Table F1 LQA Result For Sounding Made By Skudai

LQA Score Rank


06/09/2005 9 1 0 13 2 2 30 1 4 2 3 5 006/10/2005 9 1 0 0 13 2 0 5 1 4 3 2 1

06/13/2005 9 1 5 0 2 0 5 4 1 3 2 5 0

06/14/2005 9 1 30 30 30 0 2 3 4 5 1 2 0

06/15/2005 9 1 30 11 30 30 5 3 2 4 5 1 0

06/16/2005 9 1 30 0 30 30 66 2 1 3 4 5 1

06/17/2005 9 1 30 2 30 30 0 3 2 4 5 1 1

06/20/2005 9 1 30 30 30 30 30 3 4 1 2 5 0

06/21/2005 9 1 30 18 30 30 30 2 1 3 4 5 0

06/08/2005 10 1 9 14 30 30 0 2 3 4 5 1 1

06/09/2005 10 1 1 16 1 1 30 1 4 2 3 5 0

06/10/2005 10 1 4 1 2 14 15 3 1 2 4 5 006/13/2005 10 1 17 0 16 7 2 5 1 4 3 2 1

06/14/2005 10 1 30 16 30 10 5 4 3 5 2 1 0

06/15/2005 10 1 30 6 30 30 17 3 1 4 5 2 0

06/16/2005 10 1 30 0 30 25 48 3 1 4 2 5 1

06/17/2005 10 1 30 16 30 30 2 3 2 4 5 1 1

06/20/2005 10 1 30 15 30 30 30 4 3 1 2 5 0

06/21/2005 10 1 63 15 15 30 30 5 1 2 3 4 0

06/07/2005 11 1 22 16 30 30 30 2 1 3 4 5 0

06/08/2005 11 1 13 7 30 37 7 3 1 4 5 2 1

06/09/2005 11 1 6 25 3 1 16 3 5 2 1 4 0

06/10/2005 11 1 3 15 16 22 7 1 3 4 5 2 0

06/13/2005 11 1 8 1 13 18 16 2 1 3 5 4 0

06/14/2005 11 1 30 23 30 20 2 4 3 5 2 1 1

06/15/2005 11 1 30 18 30 30 23 3 1 4 5 2 0

06/17/2005 11 1 38 0 30 26 1 5 1 4 3 2 0

06/08/2005 14 2 0 0 13 7 4 1 2 5 4 3 0

06/08/2005 14 2 30 7 30 30 0 3 2 4 5 1 1

06/09/2005 14 2 2 2 9 2 0 2 3 5 4 1 0

06/09/2005 14 2 30 0 30 0 0 4 1 5 2 3 1

06/13/2005 14 2 0 0 0 0 0 1 2 3 4 5 0

06/13/2005 14 2 5 0 30 30 0 3 1 4 5 2 1

06/14/2005 14 2 148 30 30 30 2 5 2 3 4 1 1

06/15/2005 14 2 2 4 30 30 30 1 2 3 4 5 0

06/15/2005 14 2 30 0 30 30 0 3 1 4 5 2 1



163

Table F2 LQA Result For Sounding Made By Chemor

LQA Score Rank


06/09/2005 9 1 30 26 30 30 30 2 1 3 4 5 0

06/10/2005 9 1 0 0 13 2 0 5 1 4 3 2 1

06/13/2005 9 1 30 19 30 30 30 2 1 3 4 5 006/14/2005 9 1 30 30 30 7 2 3 4 5 2 1 1

06/15/2005 9 1 30 0 30 30 30 2 1 3 4 5 0

06/16/2005 9 1 30 0 30 30 66 2 1 3 4 5 1

06/17/2005 9 1 25 2 30 30 0 3 2 4 5 1 0

06/20/2005 9 1 30 0 30 30 30 2 1 3 4 5 0

06/21/2005 9 1 97 18 30 30 30 5 1 2 3 4 0

06/22/2005 9 1 30 2 30 30 7 3 1 4 5 2 0

06/07/2005 10 1 0 30 30 115 15 1 3 4 5 2 0

06/08/2005 10 1 9 14 30 30 0 2 3 4 5 1 0

06/09/2005 10 1 0 7 16 16 15 1 2 4 5 3 1

06/10/2005 10 1 49 0 15 15 30 5 1 2 3 4 0

06/13/2005 10 1 17 0 16 7 2 5 1 4 3 2 1

06/14/2005 10 1 30 17 30 0 16 4 3 5 1 2 0

06/15/2005 10 1 30 7 30 30 30 2 1 3 4 5 0

06/16/2005 10 1 30 0 30 25 48 3 1 4 2 5 0

06/17/2005 10 1 18 16 30 30 2 3 2 4 5 1 0

nurulfadzilahhasanmfke2006ttt

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