anyone know how the CB cuts the radio off?

[justfun1]

My '86 venture was missing the CB when I bought it and now I'm integrating a FRS/GMRS radio for an easy (cheap) bike to bike solution. I figured out how to integrate the unit with the bike intercom using the CB jack on the amplifier and the built in PTT switches. What I need to figure out is how to cut the radio out automatically when using the FRS (like the CB does).

 

On this web site (http://www.delusional-mechanic.com/) he identified that the center pin has 8V on it when the vox has cut out the radio.

 

My question is: Is the 8v a result of the mechanism that cut the radio out or is it the signal that is cutting it out?? In other words If I send 8V on this pin to the radio, will it cut it out the radio, blow it up or have no affect??

 

Thanks

Mike

[Owen]

His write up says the 8v mutes the radio... I would feel better if I could see a schematic...

[justfun1]

That is my thought as well. I would hate to blow up my radio testing this out!

[Monty]

I would like to see a schematic as well. Normally, a wire on the radio would detect the output signal from the CB, activating the muting circuit in the radio until the output signal goes away, then the radio resumes playing.

[Owen]

I agree that caution is best. On some transceivers, the dynamic mikes require a 6 - 9 volt bias voltage which is tied to the PTT button. It is possible that is the real purpose of the 8v at that pin...

[MiCarl]

The link you posted refers to the intercom connection.

 

I dabbled with my CB a bit this afternoon.

 

The amp deselects the radio when:

 

1 - the CB receives a broadcast.

 

2 - the PTT button on the handlebar is pushed.

 

Disconnecting the DIN cable from the back of the CB causes the amp to happily continue putting the radio through the speakers even if the PTT button is pressed or the CB receives a broadcast. Conclusion - the CB does indeed send a signal over the DIN cable to the amp causing it to switch it's input to the CB.

 

Monitoring the center pin on the CB shows no voltage to ground either with the CB not receiving, the CB transmitting or the CB receiving.

 

But hey! What's the point of having an extra CB if you can't run tests on it!

 

Turns out when the CB is receiving or transmitting it puts +6V on the pin next to the keyway in a counter clockwise direction. On the cable it will be the 1st pin clockwise from the keyway.

[scotty]

Its an 8V output when you speak loud enough to mute the radio. I never sent anything down it. (too scared!)

It wouldn't surprise me to see the radio mute have something to do with the unknown mystery pin, but again, I didn't try that ether.

I would have liked a schematic also! Don't forget to read the "big disclaimer"

Hope this helps, Scotty

[scotty]

On this web site (http://www.delusional-mechanic.com/) he identified that the center pin has 8V on it when the vox has cut out the radio.

 

 

Thanks

Mike

In hind sight that was a poor choice in wording / terminology on my part. I think I have it fixed.

[Owen]

Thanks guys for the info. I have not really looked very deeply at the onboard audio system. I like the way it operates. But it gives me some insight as to how I can more cleanly integrate my ham rig.

[justfun1]

Wow . . . Thanks for all of the input!

 

MiCarl . . I just want to clarify that I understand exactly which pin you are talking about. To cut the radio out it sound like you need to send +6v to the pin that is the first one clockwise from the keyway when looking at the cable plug that connects to the CB?

 

Scotty, I was not exactly sure if your graphic was drawn in referance to the cable plug or the amp plug looking from the top. Is this pin the unknown one in your graphic?

 

Thanks again for all of your help.

 

Mike

Edited April 26, 2009 by justfun1