about yaa trap

COAX Stub Filters for MM Contest Station,

So Called “YAA Trap”Key Points of Multi Band Trap

using Coax Stubs

JA1CTB (JA7TNO) Tetsu Tanizawa “Aki”

113年11月18日月曜日

About YAA Trap

• Original Article was introduced to Japan by QST through CQ Ham Radio(JP) in 60’s

• JA7YAA, Club Station of Tohoku University, tried this idea in 1975, because it looked easy and not expensive for university students

• It gives good isolation for band to band in Multi-Multi Contest Operation

• So far, JA7YAA has become very active in contests, and this Coax Stub has become known as YAA Trap amongst the Japanese contester HAMs

213年11月18日月曜日

Basic Implementation and Theory

• Open Ended 1/4 λ Stub shows Short condition (Zero Impedance)

• Short Ended 1/4 λ Stub shows Open condition (Infinite Impedance)

• Combinations of above are used

• These Stubs give a null condition or no effect at the connecting point depending on the Observed Frequencies

• The null points will appear in every 1/2 λ from the stub point along with the main

313年11月18日月曜日

Z-Chart of Open & Short Stub

• Open Stub

• Impedance = ∞ at (2n)/4 λ for n = 0, 1, 2, 3, 4, ...

• Impedance = 0at (2n+1)/4 λ for n = 0, 1, 2, 3, 4, ...

• Short Stub

• Impedance = ∞ at (2n+1)/4 λ for n = 0, 1, 2, 3, 4, ...

• Impedance = 0at (2n)/4 λ for n = 0, 1, 2, 3, 4, ...

-300 j ohm

-250 j ohm

-200 j ohm

-150 j ohm

-100 j ohm

-50 j ohm

0 j ohm

50 j ohm

100 j ohm

150 j ohm

200 j ohm

250 j ohm

300 j ohm

0 0.0625 0.125 0.1875 0.25 0.3125Stub Length at f [λ]

Short Stub f Open Stub fShort Stub 2f Open Stub 2f

413年11月18日月曜日

Examples to Understand Basic Theories and Physical Structures

• 28MHz Trap for14MHz TRX --- basic

• 28MHz Trap for14MHz TRX --- extension

• 21MHz Trap for 7MHz TRX--- extension

513年11月18日月曜日

28MHz Trap for14MHz TRX --- basic

14MHz 1/4λShort Stub

~

14MHzimpedance = ∞

=> Z0 with coax Q

28MHz impedance = 0

=> null at 28MHz

14,1000

→ ANT

Hot Point!Vmax << COAX VmaxShort Ended

Stub must be here !

Hot Point!Vmax << COAX Vmax

Voltage Standing Wave Distribution on a Stub in Different Frequencies

V = max

Hot Point!Vmax << COAX Vmax

Hot Point!Vmax << COAX Vmax

Hot Point!Vmax << COAX Vmax

↑ 28 null ↑ 28 null ↑ 28 null↑ 28 null

613年11月18日月曜日

28MHz Trap for14MHz TRX --- extension

Center Feed14MHz 1/4λShort Stub

~

14MHzimpedance = ∞

=> Z0 with coax Q

28MHz impedance = 0

14,1000

Stub must be here !

14MHz +j50ohm14MHz -j50ohm

28MHz impedance = ∞

Short Ended

Open Ended

Parallel Resonancegives impedance = ∞

28MHz impedance = 0

=> null at 28MHz

Voltage Standing Wave Distribution on a Stub in Different Frequencies

→ ANT

↑ 28 null ↑ 28 null ↑ 28 null↑ 28 null

Hot Point!Vmax << COAX Vmax

Hot Point!Vmax << COAX Vmax

Hot Point!Vmax << COAX Vmax

Hot Point!Vmax << COAX Vmax

713年11月18日月曜日

28MHz

28MHz TRAP for 14MHz Operating Point in Z Chart

-300 j ohm

-250 j ohm

-200 j ohm

-150 j ohm

-100 j ohm

-50 j ohm

0 j ohm

50 j ohm

100 j ohm

150 j ohm

200 j ohm

250 j ohm

300 j ohm

0 0.0625 0.125 0.1875 0.25 0.3125Stub Length at f [λ]

Short Stub f Open Stub f Short Stub 2f Open Stub 2f

~

14MHz 1/8λ Short Stub

14MHz 1/8λ Open Stub

28MHz 1/4λ Open Stub

28MHz 1/4λ Short Stub

28MHz 1/4λ Short Stub

28MHz14MHz 14MHz

813年11月18日月曜日

Hot Point!Vmax << COAX Vmax

21MHz Trap for 7MHz TRX extension

Offset Feed7MHz 1/4λShort Stub

~

7MHzimpedance = ∞

=> Z0 with coax Q

21MHz impedance = 0

7,1000

7MHz +j90ohm7MHz -j90ohm

21MHz impedance = 0

Short Ended

Open Ended

21MHz impedance = 0

=> null at 21MHz

Hot Point!Vmax << COAX Vmax

Parallel Resonancegives impedance = ∞

Voltage Standing Wave Distribution on a Stub in Different Frequencies

→ ANT

Hot Point!Vmax << COAX Vmax

↑ 21 null ↑ 21 null↑ 21 null

Hot Point!Vmax << COAX Vmax

↑ 21 null

913年11月18日月曜日

Short Stub f Open Stub f Short Stub 3f Open Stub 3f

-300 j ohm

-250 j ohm

-200 j ohm

-150 j ohm

-100 j ohm

-50 j ohm

0 j ohm

50 j ohm

100 j ohm

150 j ohm

200 j ohm

250 j ohm

300 j ohm

0 0.025 0.05 0.075 0.1 0.125 0.15 0.175 0.2 0.225 0.25 0.275 0.3 0.325Stub Length at f [λ]

21MHz TRAP for 7MHz Operating Point in Z Chart

~

7MHz 1/8λ Short Stub

7MHz 1/8λ Open Stub

21MHz 1/4λ Open Stub

21MHz 1/4λ Short Stub

7MHz 7MHz21MHz 21MHz

1013年11月18日月曜日

Implementation Examples

• For 3.5MHz TRX, trapping 7, 14, 21, 28MHz

• For 7MHz TRX, trapping 3.5, 14, 21, 28MHz

• For 14MHz TRX, trapping 3.5, 7, 21, 28MHz

• For 21MHz TRX, trapping 3.5, 7, 14, 28MHz

• For 28MHz TRX, trapping 3.5, 7, 14, 21MHz

1113年11月18日月曜日

For 3.5MHz TRX, trapping 7, 14, 21, 28MHz

• 3.5MHz 1/4 λ Short Ended Stub∞@3.5MHz, Null@7, 14, 21, 28MHz

3.5MHz 1/4λShort Stub

~

3.5MHzimpedance = ∞

=> Z0 with coax Q

7, 14, 21, 28MHz impedance = 0

=> nulls1213年11月18日月曜日

For 7MHz TRX, trapping 3.5, 14, 21, 28MHz

• 3.5MHz 1/4 λ Open Ended StubNull@3.5MHz, ∞@7, 14, 21, 28MHz

• 7MHz 1/4 λ Short Ended StubNull@14, 28MHz, ∞@7, 21MHz

• 7MHz 1/4 λ Short Ended Stub with Off Set Null@21MHz, ∞@7MHz

3.5MHz 1/4λOpen Stub

~

7MHz 1/4λShort Stub

~

21MHz 1/4λOpen Stub

~7MHz 1/4λ Short Stub

with 21MHz 1/4λ Off Set1313年11月18日月曜日

For 14MHz TRX, trapping 3.5, 7, 21, 28MHz

• 3.5MHz 1/4 λ Open Ended StubNull@3.5MHz, ∞@7, 14, 21, 28MHz

• 7MHz 1/4 λλ Open Ended StubNull@7, 21MHz, ∞@14, 28MHz

• 14MHz 1/4 λ Short Ended Stub with Center Feed Null@28MHz, ∞@14MHz

3.5MHz 1/4λOpen Stub

~

7MHz 1/4λOpen Stub

~

28MHz 1/4λOpen Stub

~14MHz 1/4λ Short Stub

with Center Feed1413年11月18日月曜日

For 21MHz TRX, trapping 3.5, 7, 14, 28MHz

• 3.5MHz 1/4 λ Open Ended StubNull@3.5MHz, ∞@7, 14, 21, 28MHz

• 7MHz 1/4 λ Stub + Off Set 7MHz 1/4 λ Short Stub Null@7MHz, ∞@21MHz

• 14MHz 1/2 λ Short Ended Stub Null@14, 28MHz, ∞@21MHz

3.5MHz 1/4λOpen Stub

~

7MHz 1/4λ ~

14MHz 1/2λShort Stub

~

7MHz 1/6λShort Stub

21MHz 1/4λOpen Stub

1513年11月18日月曜日

For 28MHz TRX, trapping 3.5, 7, 14, 21MHz

• 3.5MHz 1/4 λ Open Ended StubNull@3.5MHz, ∞@7, 14, 21, 28MHz

• 7MHz 1/4 λ Open Ended StubNull@7, 21MHz, ∞@14, 28MHz

• 14MHz 1/4 λ Open Ended Stub Null@14MHz, ∞@28MHz

3.5MHz 1/4λOpen Stub

~

7MHz 1/4λOpen Stub

~

14MHz 1/4λOpen Stub

~

1613年11月18日月曜日