FT290 CW KOX Circuit
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WW on Wed Dec 11 05:57:59 2024
To : TECH@WW
By G8MNY (More Graphics Feb 06)
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This is not actually break-in but just a KOX circuit.
N.B. It can only be used on the CW mode otherwise it keys up the Tx !
Only very light currents are used in these rigs for the CW & PTT Lines & also a pulse detection circuit makes some KOX circuits unworkable.
ÚÄ +6.8V
22K
___________________________\ CW Jack \____³__CW LOGIC
³ ³ ³ / @ Rear /
³ ³ _³_
³ 1M /_\ ÚÄÄÄÄ10KÄÄÄÄÄÄ> +5V R I G
³ ³ ³D1 ³ Pin 4 C I R C U I T S
³ ÃÄÄÙ ³ æPROC
³ ³ ³ ÚÄÄÄ> PTT >ÄÄÂÄÄ´<ÃÄÄÄ LOGIC
³ ³ ³ D3 ³/ Pin 3 ³
³ ³ ÃÄÄ´>ÃÄÄ´T2 ÀÄÄÄ´ÃÄÄ Pulse
³ ³ D2 ³/ ³\e M I C Circuit
³ ÃÄÄ´>ÃÄÄ´T1 ³ P L U G
³ ³+ ³\e ³
CW ___³ === C1 ³ ³
KEY X_______³_________³_________³____ GND
Pin 1
T1,T2, = BC109 (high gain NPN)
D1,2,3 = 1N4148
C1 = 1 2.2 3.3 4.7uF depending on hang time wanted
HOW IT WORKS
1/ With the Key up, T1 is turn on by 1M & D2, the 1M is high enough not to load
the CW circuit. T1 on keeps T2 turned off.. PTT high, Rx Mode.
2/ On key down, D1 instantly discharges the C1 & turns off T1. T2 is tuned
on by the 10K & D3 from the MIC's +6.8V line. PTT goes Low... TX ON.
3/ In between key downs C1 starts to charge up from the 1M & if it reaches
about 1V D2 conducts & T1 will turn on & state 1/ is reached. Otherwise
further key downs repeat state 2/
PROBLEMS
If T2 does not operate rig properly, test PTT volts go from around 5V to 0.3V. Adjust the 10K if needed.
If the hang time is too short try increasing the C1 to 2.2/3.3/4.7uF. etc.
P.S. I have only breadboarded this circuit & tested it on FT290/690/790 mk 1 so far, after Andy G0FTD wanted to know how to etc, & would like comments.
Why Don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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