1. ic-765 maintenance & improvement 2. multiband full-size ... · 12/16/2008 · kcc meeting...

KCC meeting 2008-12-16 Internal review purpose only! 1

1. IC-765 Maintenance & Improvement

2. Multiband full-size vertical

3. Balun improvement

KCC annual meeting

December 13, 2008

HL3AMO/박기준

KCC meeting

1. Initial works done on IC765

• DOA: Antenna tuner cannot find SWR min (Not working!).

– A BAD 1N60 diode on the detector unit of tuner

– Replaced both (bad and good) diode with matched pair

• Adjust R# & R# on tuner controller

• Adjust TC# on detector unit

– WORKS FINE

• MAIN tuning knob is very tight!

– OLD rig, need cleaning and some oil

• Removed dial assembly, take parts

• Cleaned stuck shaft, aged oil, and residues; Add some silicone oil

• Re-assemble parts, some oil at shaft tip

– WORKS VERY GOOD

• It is wired 117V: Need 220V connection

– Cut a wire in the PS unit, adjust voltage of needed (at 20A, 220V)

• Some problems with diagram reading (Be careful!!)

• My mistake: Replaced a burn resistor and the 2SA1015 with 2SC1815

2008-12-16 Internal review purpose only! 2

KCC meeting

Maintenance: Tuning Knob


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2. Modifications done on IC-765

• Initial adjustments (as given in SM)

– Adjust VCO voltage at PLL board

– Set reference oscillator, etc.

– RX gain, TX stuff, AF etc.

– Problems

• RTTY SHIFT adjustment, TOTAL gain, S-meter gain (Experience & skill!)

• Modifications

– Famous PBT mod.

– T/R switching mod.

– Full QSK Keying improvement Mod.

• QSK keying delay

• Improved sidetone

• Improved waveform (risetime)

– Fast AGC decay mod.

• Fit to your need


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2-1. PBT mod.


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2-2. Improved T/R switching mod.


2. Remove screws from Main Unit and lift board

3. Remove R10 (39K) and R11 (39K) near IC-2

4. Install one end of new R11 (150K) to foil trace which connects to C13. Insulate remaining lead of R11 and solder it to Pin 3 of IC-2

5. Install new R10 (47K)6. Solder D159 (1SS53) between Pins 3

and 13 of IC-2. Cathode side of diode (striped end) goes to Pin 3

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2-3. Full QSK & Keying improvement

• Improve QSK Keying

– To increase the keying weight in the Full Break-In mode add a 0.022 mF capacitor as shown in Figure

• Improve the sidetone

– Solder a 51k 1/4 watt resistor between the left ends of components labeled 15 and 81

• Improve CW waveform (increase risetime 2.5=> 5 ms)

– changing C108 on the main board from 4.7 uF to 10 uF. (Note: this is a tantalum cap)


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2-4. AGC improvement

• Check values of C280, C300: should be 0.22 and 0.1 uF

– Change C300(0.22uF) to about 1~2 uF

– Change C280(0.1uF) to about 0.3~0.5 uF

• Change R440(1kW)

– about 470-ohm


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3. Future: Roofing filter?

• Really need a roofing filter?

• 1st IF = 69.0115 MHz for IC-756, 765, 775

• Is it worth ~$200 ?


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Retrofit: 455 kHz CW filter (JRC-> Icom)


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Retrofit: Add shielding cover


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USB-Serial<>CI-V IF


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Balun modification

• Transmission transformer: line Z = 50-ohm

• Turns depends upon used Frequency range


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Fiber glass telescopic poles

• Fiber glass poles

– Fishing pole: OD, Typical length ~ 6 m

– COS pole: OD 25/50, Length up to 10 m

• Usage

– Rotary dipole : full size for 30 m, Reduced for 40 m band

– Vertical top: up to 80 m band

• Wiring

– Loose spring: 1~2 turn per meter

– Copper taping

– Wire inside of the tubing

• Caution

– Weather seal: taping at each section


KCC meeting

3-Band (80/40/30) vertical - Model


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3-Band vertical – VSWR plot


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3-Band vertical: Radiation plot


KCC meeting



1. ic-765 maintenance & improvement 2. multiband full-size ... · 12/16/2008 · kcc meeting...

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