[Elecraft] K3 PTT with DEMI Transverters

[Ken Kontor]

Gentlemen,

I am looking for a circuit that one of you K3 users may have designed to 
automatically switch the K3 PTT line between multible external 
transverters as the K3 is switched from band to band.

I presently use the K3 PTT line to key my 6m amp driven with 30 w from 
my K3.

I recently purchased a DEMI 2m HP transverter to drive my 2m 3CX800 amp. 
The DEMI puts out 50 w with 1 mw of drive from the K3. The problem I 
have is when I key the DEMI Transverter from Pin 10 on the K3 15 Pin 
accessory socket, the K3 PTT out on the back of the K3 also Keys my 6m 
Amp even though the K3 is set to 2m. I need a circuit that will decode 
the BCD output from the K3 15 Pin connector to key the 6m Amp when I am 
on 6m and automatically switch the PTT line to the DEMI Transverter when 
I am on 2m. A manual switch would be very inconvenient for VHF 
contesting as one need to quickly QSY between bands with one station for 
multiple points. Also in the future I might add a 432 Transverter and 
would like to auto switch  the PTT for it also. I would only require 
three outputs as I would only switch between 6m, 2m and 70 cm.

I am a Mechanical Engineer with limited Electrical knowledge. I did 
build  a K2 and can breadboard stuff from a schematic and parts list, 
but I am not a circuit designer and have no knowledge of digital logic 
stuff other than I know it exists. I am in need of a designed and tested 
circuit that is know to work reliably. Given the circuit diagram and a 
parts list I could then reproduce it.

Your help is greatly appreciated. Thank you in advance for any 
information you can provide.

73, Ken - W8KEN


PS: you may contact me off line at w8ken at yahoo.com