[WT-support] PTT keying

[Olivier F5MZN]

Stewart GM4AFF a écrit :
> Thanks for all the replies. Maybe it's me, but the diagrams on page 181/2 of
> the manual show a COM port or parallel port CW keying arrangement - not PTT.
> I've made these interfaces before. Neither of these show how you would
> interface the port with the radio's PTT. Does pin 16 on the LPT port or pin
> 7 of the COM go high or low when 'keyed'? How much current could these pins
> sink? Not much - not a relay? So could the circuits be extended with another
> 1k resistor and another transistor from the appropriate pins? These would
> close the PTT from LPT pin 16 or COM pin 7? Apologies for the persistence,
> but I'm not an electronics engineer and it still isn't clear to me.

Affirmative. You can build the exact same circuit for the PTT control.

Usually, for a COM port, the pin4 (DTR) outputs CW when the pin7 (RTS) 
outputs the PTT control. This is a "common standard", however you can do 
the opposite because WT lets you choose which pin of the COM port will 
output CW keying and which one will output PTT events.

Most radio interfaces don't need DTR nor RTS for the CAT control. So 
that, the same COM port can be shared for both the CAT interface and the 
CW/PTT control.

For an LPT port, Win-Test does send the CW signal on pin 17 and PTT 
signal on pin 16. Note that this must be enabled in the "Interface 
configuration" window (LPT configuration).

Hope this helps, Steewart.

73,
-- 
Olivier / f5mzn