Problem with COM port radio keying

[mr_fx]

I have been spending the last few hours trying to get DM780 to work with a COM port (RTS/DTS) keyer I built...

It works fine on 432, 144, 50, and 28Mhz... However When I dropped down to 21 and 14Mhz and Key up it locks in transmit...

NOTE: into a dummy load this does NOT happen

I have not tried it into other rigs for this purpose,

Also manually using the key does not lock into CW TX...

another thing to note: I have also tried doing a continuity test into my Digital Volt/ohm meter, it worked great and was REALLY funny to listen to @ 100WPM lol


This is the keyer I built

http://www.logger32.net/help/Logger32/Configuring Push To Talk.htm

The only way to stop the radio from keying if if gets locked is to unhook one of the leads coming off of the COM port keyer...

 

[Captain Kilowatt]

That is the same cct I used to key my FT-857. Your problem is RF getting into it. You should be using shielded cable and a shielded connector. If you are and still have problems slip a ferrite or two over the cable. If it still happens solder a capacitor of about 0.01 uF from the junction of R1 and D1 to ground.

 

[mr_fx]

Thanks Captain KW,

That was kinda my first guess too...

time to clean the setup up a little bit

Would an A/V style cable be good enough?

 

[Captain Kilowatt]

Any type of shielded cable will work. I had some shielded two wire cable (two conductors with a shield) that I used. Surplus from my work in the business days from years gone by. Oh and use metal connectors not the plastic type.