[Elecraft] com port PTT question

[Don Wilhelm]

If you are directly connecting a serial port signal pin to the K3 ACC 
PTT, that will cause trouble, and may damage the K3.  The voltages out 
of a serial port can be up to 25 volts, both positive and negative.  You 
need some sort of conversion (a single transistor keying circuit) to 
drive the K3 PTT input between 5 volts and ground levels.

On the other hand, the K3 already has provision for PTT and Keying 
through the serial port DTR and/or RTS signals.  You probably have a 
serial cable between the K3 and the PC for loading firmware, so use that 
connection and set the CONFIG: PTT--KEY menu to whichever line your 
software is using for PTT.


73,
Don W3FPR

On 9/20/2011 11:42 AM, DK5EW wrote:
> Hello all,
> I have a small problem with PTT via com port and ACC plug.
> I made a 2 pin cable 9pol from PC to ACC 15pol to K3.
> I soldered pin 4 for PTT and pin 5 for ground.
> I tested it for correct wire and short - all O.K.
> Now as soon I connect the TRX-ACC and the com port (serial 9 pin) to my
> PC the K3 goes on TX.
> Any solution out there ?
>