Homebrew Digimode Interface

For several years I used a very simple interface with just DC isolation and full Ground connection between my computer and radio for Digital modes. Realizing that I was living on borrowed time before something blew, I decided to do a full galvanic isolation interface. At the same time my ARC experimented with a computer-based contest interface (CQ_caller aka voice recorder/player and CW interfacing), requirering some way of signaling the computer what to do from push-buttons and/or footswitches.

Another  very good design with "hard" CW keying can be found here: http://www.cqrlog.com/?q=webfm_send/86/3

This is my design:

T1/T2 are 600Ohm LF transformers (salvaged from discarded telephone equipment); IC1/IC2 are optocouplers (same source)

(Click on picture to get a full resolution version)



The operational prototype boxed and ready to go! (In daily use in my schack)


I also constructed a "Soap-on-a-Rope" mini-version for portable use, omitting the pushbutton interface:

The cable between the interface box and the radio is attached via a 5-pin DIN plug, and is thus easily exchangeable if a another 

radio needs attachment!


Both interfaces are used with several Digimode programs (WSJT, CW-Get and -Type, MMTTY, PSK31, W95SSTV, WINMSDSP 2000 and others) and have been in nearly daily use for almost a year.


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Last modified 09.10.2011, Peter Frenning