By

Geoff Haines, N1GY

            Let me say right at the start, that I did not originate this idea. I have seen several articles in several different amateur radio magazines on this idea over the years. When I found that I had a need for this device, it seemed obvious that I would need to build it.

            The concept is very simple. Take a commercially available switch box intended for switching data lines such as printer cables between two computers, and change out the connectors so that it can be used to switch between two microphones to one transceiver.

            The best data switch box to use has a rotary switch knob and a multi-layer switch that controls 25 lines from one DB-25 connector out to two DB-25 connectors in. The switch works both ways, that is one line in to two lines out or two lines in to one line out. Most of these devices do not use color coded wiring. The one I used had maybe 8 or 9 blue wires going from the switch to each of the connectors, the other wires were all orange. This could be a problem if one was expecting to use the color code to keep the wires organized.

            There is an easy solution to this seeming problem. Just do not cut any wire off the DB-25 connectors until you are ready to solder it to your microphone connector. Then cut the same wire in the same position on each of the three connectors and solder each wire to the same position on each of the three mic connectors. Do each wire set one at a time old connector to new connector and you will have no problem.

            After you have filled all the contact positions in your microphone connectors, and any supplemental connectors such as the external speaker/ headphone plug selection, simply cut away the rest of the wires to the old DB-25 connectors and remove them. Now is the time to add the jack for the external PTT switch, if needed. It usually just gets wired across the contacts for PTT that connect to the Boom Mic in parallel.

            Now modify the chassis box to accept your microphone connectors as necessary and install the mic connectors in the box along with any other jacks that may be required such as external speaker, earphone jack, or PTT switch.

            After you test the selector switch to make sure that both mics work as they should, that the PTT switch on both mics works, etc. then proceed to dress up the box as needed. A new label for the selector switch is all that is really required, but you may also paint the box if desired.

            Now that the selector switch is finished, it is time to plug in both microphones, the external speaker (if used) and the PTT foot switch (if desired).

Plug the selector into the radio’s microphone jack and the external speaker plug into the selector. Plug a patch cable if used into the radio’s external speaker jack and into the selector. That’s it. You are all done. Now sit back and make some contacts with the radio.