CB Radio to intercom

[thirdbike]

There must be a few electronics wizards out there.

 

I have a IMC Motorcom 100 intercom on my Venture. This unit works fine in intercom mode but can also handle Ipods, cel phones, VFR and CB radios. I have added a Cobra mobile radio. The unit is mounted into the space where the tape deck normally goes. There is a remote handlebar PTT button.

The problem is that the intercom unit has a three contact 3.5 mm stereo plug that serves as both the mike and speaker connectors. The CB radio has an external speaker mike and a standard four pin microphone jack consisting of TX,RX, Audio and Shield. I can get speaker sound to the intercom using one contact to the TX pin. No combination of pin-outs seems to make the transmit work through the helmet mike.

 

I trust there is a simple answer. Can you please indicate how this unit should be wired?

 

Thank you

[GeorgeS]

OK, as I understand it, you want to take the Intercom Audio, from the aftermarket Intercom system, and the Mic Key signal, and tap them into the other commercial CB radio.

 

If this is correct:

 

I would start by looking at getting the Key signal, and the audio output from the Intercom system, ( find these connections )

 

then you are going to have to tie them into the CB somhow.

 

The Key signal ground signal to the CB should be easy.

 

The Audio, After you tie into it from the intercom system, you will probably have to run it thru a Small Audio Isolation Transformer.

( you can get these at Radio Shack )

 

You will probably have to open the Cable from the CB to get access to the connection points.

 

I would reccomend opening up the CB case, and find a point where you can solder New Wires, for a New cable you must fabricate, to get the Key signal, and audio input from Intercom onto the Mic, audio input point. ( with the inline audio transformer, {{ you might be able to find space in the cb unit to mount it. }} )

 

 

Also, do a Google search for CB Schematics, you might be able to find a schematic for your CB Radio. This would be a big help.

 

You don't give much info, so I am shooting in the Dark Here .

[stardbog]

Does Motocom come with their own line of helmes speakers/ mike?. From My point of understanding your question is you have hard time to figure out how to wired helmet mic to unit... Is that rigt ?

I Use to have simular ( British ) Version ot Autocom, and I wasnt able to use autocon helmet speakers / mic. with venture cb/ intercom system.

You have to use Motocom Helmet Speakers/ Mic. with Motocom Master unit.

I Gues you have CB hendheld unit connected to Motocom unit with Speakers/ mic cable.

Check out Jacks... One is 3.5mm stereo, second is 2.5mm mono jack.

 

Give us some more info wich CB ( Brand/ Model) you are trying to connect.

[thirdbike]

Thanks guys. Here goes:

 

The after-market intercom unit is a "IMC Motocom MIT 100." It is new and fully functional as a helmet intercom. Although described as being able to hook to nearly any audio device, instructions did not come with the unit nor are they on the company's website. It has a three contact 3.5 mm plug which after hounding the distributor ( finally I called direct), I am led to believe has the Mic contact as the outermost and the Speaker as the middle contact. They didn't explain what the last contact was for but I am assuming it is a common ground.

 

There is a six pin mini Din plug on the black box that connects via a Y extension cable to the PTT switch which has a 4 pin mini Din plug. The other end of this Y cable is the 3.5 mm referred to above. In addition the MIT 100 has a female 3. 5 connector marked audio as well as another 3.5 male plug that I believe is intended for cel phones.

 

The CB radio is a "Cobra 19 DX IV" which I chose for its compact size but full functionality and full external antenna. Yes, I bought the adapter cable to hook the MIT-100 to a CB radio but this is for hand-helds and so I returned it as the Cobra is a mobile unit.

 

As mentioned before, the Cobra has an external speaker jack. and the four pin mike connector is easily accessible from inside in order to make up a patch cord. With the microphone disconnected from the microphone jack, the CB radio has no audio. As noted before, the manual indicates that the four pins serve as TX, RX, Audio and Shield. I tried hooking it up via some jumper cables and got audio via the TX and Audio connections to the speaker and what I referred to earlier as the common connection or the innermost contact on the 3.5 mm plug on the MIT-100. This setup disables the built-in speaker on the CB, which I believe is correct but somehow this hookup doesn't sound right. No amount of fiddling could get the PTT switch to activate the helmet speaker. The only thing I didn't do was buzz the extension cable and PTT switch for connectivity.

 

I hope this explains things a bit more clearly. Again thank you for your assistance.

[stardbog]

Thirdbike quote:

"The CB radio is a "Cobra 19 DX IV" which I chose for its compact size but full functionality and full external antenna. Yes, I bought the adapter cable to hook the MIT-100 to a CB radio but this is for hand-helds and so I returned it as the Cobra is a mobile unit. "

Motocom is designed to work with handheld CB Radios only. Motocom have special cable wich you have returned. I Would recomand one of this units:

 

[ame=http://www.amazon.com/Midland-75-822-Handheld-Vehicle-Adapter/dp/B00000K2YR]Amazon.com: Midland 75-822 Handheld CB Radio with Vehicle Adapter: Electronics[/ame]

 

Compact design, same futures as Truck Model, Weaterproof, and plug and play connectors to work out of box with Motocom Intercom unit.

 

Dont know how to integrate Truck / Desktop CB in to motocom.

 

:080402gudl_prv:

[thirdbike]

Thank you for the help and suggestions.

 

I am wondering if there is anyone else with suggestions on what to try?