Single Mic w/ 2 Radios

[nick.dejohn]

I have 2 Motorola CDM1550's and obviously I am using seperate microphones. I was wondering if I could purchase or make a system that would allow me to use one mic and a toggle a switch between the two radios, depending on which one I would need to transmit on. Anyone have any ideas on what to use or do?

Thanks,
Nick

[thebigphish]

cheap make? yes. will it work? yes. might it damage the radios? i don't know.

I have an old VGA monitor switch (a/b) w/ one input. It's essentially a 15 rotary toggle, that switches all 15 pins thru on the cabling to separate outs. If i wanted to do something like what you said you need, i would take a piece of cat 5 - and i would make a female RJ-45 to male DB-15 connector (probably using stuff from Cables & Connectors ::plug:: gotta love walking distance) jumper cable, and i would plug in the single mic into that.

Then i would make two separate DB15 to RJ-45 male jumpers, plug one of each into the radios, and the corresponding separate ends into the toggle box.

It goes w/o saying that you would need to make sure that the pins were EXACTLY the same for both cables, and that you keep the circut integrity in place by matching wire to wire, but it would work. I would say maybe 30 minutes?

YMMV. And there are probably some easier ways to do that, but that is what i would do...should i ever need to do that. Honestly, i wouldn't. I would throw a dual deck system in.

[wavetar]

It's easy enough, I set one up for a customer a few years ago when they were in the midst of switching between systems & needed to transmit over the 2 systems at the same time. You can parallel the connections such as ground & PTT. You also parallel the MIC HI lines, but put a DC blocking capacitor on one of the lines, as you only need to bias the mic element with voltage from one radio. It's easiest to do it with an RJ45 junction box & wiring into the rear accessory connectors of both radios, if available, but can just as well be done wiring into the front mic connectors.

Todd

[nick.dejohn]

Todd:

Thats sounds great! I was kinda of hoping I could fin something that I could just plug into the back of the radios nd be done. Call it lazy or just not wanting to bother with it. If you are familiar with Middletown, Connecticut; the Middlesex Paramedcis have a system attached to 2 CDM1250's with led's to show which radio was be utilized and they have a toggle switch mounted in the console that allowed them to switch between the two radios.

If anyone knows of something easier to do or buy, let me know. If you are intersted in building it for me for a fee, let me know.

Thanks,
Nick

[RKG]

For what it is worth, most GA aircraft have a panel on the dash that permits selection and mixing of Rx audio and selection of one of two or three transmitters, all from the same mike and speaker (or headset). However, simply because of the aircraft designation, the products tend to be expensive.

E.g.:

https://buy.garmin.com/shop/shop.do?cID=199&pID=93

[nmfire10]

For what it is worth, most GA aircraft have a panel on the dash that permits selection and mixing of Rx audio and selection of one of two or three transmitters, all from the same mike and speaker (or headset). However, simply because of the aircraft designation, the products tend to be expensive.

E.g.:

https://buy.garmin.com/shop/shop.do?cID=199&pID=93

I would have never thought of using an aircraft audio panel for a car but that is a great idea. Be prepared to spend several AMU's for a new audio panel. Used, they go for about 1/2 of an AMU.

[jackhackett]

You might try a rotary switch, you can find them with multiple poles easier than you can a toggle. You could probably use a 4 pole 2 position switch, connect the GROUNDs together and use 3 of the poles to switch PTT, MIC HI and HOOK, and the 4th to switch LEDs to show which radio is connected to the mic. Make sure you get a non-shorting type switch (break before make).

[aaknitt]

I'm going to do a slight hijacking of this thread and pose a similar question. I've got remote base setup with two GM300s with two mics. I'd like to keep the two mics, but rig it so that when one mic is keyed only one of the radios is keyed, but when the other mic is keyed it keys both radios. Here's what I was thinking:



In this case, when the UHF mic is keyed, I was thinking it would key both radios by allowing current to flow from both PTTs to ground. When the VHF mic is keyed, the diode would block current from flowing from the UHF radio and only the VHF radio would key up. wavetar's point about a DC blocking cap is a good one, and I can easily add that. My question is whether the diode scheme shown above would work. Also, both mics would be hot regardless of which one is keyed. Would I need to worry about cancellation from phase differences? Any thoughts are welcome.

Thanks in advance,

Andy

[ayaresr]

FWIW: We use a unit made by FireCom in our truck here. Has two radio interface, intercom (we use the headsets) and digital instant recall playback. Works very well, you select radio a or b on the front panel. Motorola mics still work individually on the radios, or can be done through the ptt on the headset. Not sure if thats similar to what your looking for or not.
Ryan