N1GY- The simple Approach to Ham Radio
and My Model Railroad Hobby
This diagram is for radios using an RJ-12 or CAT 3 connector (6 pin modular)
This diagram is for radios using the RJ-45 mic connector
This is a new picture of the latest mic selector using the circuit above. Originally designed for the IC-706 (all variants) and 703, it can also be used for any radio that uses an RJ-45 connector for the mic input like the Yaesu FT-857, FT-897, FT-817 etc. All 8 wires from the female RJ-45 jacks are switched and the two lines for the external speaker/headphones jacks are switched simultaneously on a different set of contacts. If one uses a headset for operating as Net Control but a hand mic for rag-chewing, the change is made with a flip of a knob rather than plugging and unplugging fragile cables. On the 706 series of radios, which includes the IC-7000, all of the connections can be made at the back of the radio so no extra cables show in the front. The basis for the selector is a Data Switch, now pretty obsolete since the development of USB. They can still be found at hamfests and computer shows if one looks for them. There is not much to the conversion technically, just a lot of tedious soldering and the creating of new openings to fit the RJ-45's and the holes for the external speaker and earphone jacks. You will need at least a 15 pin Data Switch to handle all 10 lines but they are very common.
You will note some changes in the circuit as built in this version and indeed in all of the recent versions. First I have eliminated the separate PTT jack as the headset adapters that I build and indeed most commercial headsets have the PTT built into the cable to the radio. Second, the cable connecting the external speaker jack on the radio to the selector is now built in to the selector and does not require a separate jack. Third, I have moved (most of the time) the RJ-45 female jacks to the front of the selector box rather than the back. The selectors that I use here at my station have the hand mic jack in the front and the headset jacks are in the back because I have built extensions to bring the headset jacks out to the front in places on the operating desk that are more convenient for me.
This selector can also be built using RJ-12 6 pin jacks and plugs for the Yaesu FT-7800, FT-7900, FT-8800, FT-8900, FTM-100 and FTM-400 series of radios. The same concept is used, all of the mic lines are switched straight through and the 2 lines for the external speaker/headphone jacks are separate but switched simultaneously.
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.