Had a Cobra 29 radio that wasn't transmitting at the elevator today. I could hear others, but no one else could hear me. Sometimes it would transmit fine for a few seconds then it would cut completely off. No static, no sound from keyed mic, nothing. A weird thing is that I can sometimes be heard, but I can't be the first to say something. By that I mean if someone else talks, then I can respond briefly for a few seconds before the radio stops transmitting. If I talk first, like when approaching the inbound scale, it wont work.

I did a little troubleshooting this evening...


First thing I did was calibrate the SWR. Everything checked fine and the reading was fantastic, but it still wouldn't transmit.

Since I can hear others fine I tried a different mic (actually three different mics). No change.

After that I went to the antenna (even though the swr cal was great)... Everything seemed intact, but I tried two different temporary magnetic antennas Just in case. Same result.

At this point I assumed the radio was bad so I popped in a brand new Cobra 19 we keep as a spare. Still did the same thing.

Finally we assumed it was bad power so we hooked the CB directly to the truck batteries with no luck. Tried both CB radios and multiple antennas direct to battery. All combinations had the same problem.

It seems to be something with this truck because radios work great in other trucks. It's not local interference or anything.



I'm completely puzzled. Does anyone have an idea what I can do? I appreciate any tips I could get. Thanks!