CB not transmitting?

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alkarich

alkarich

10 Year 15 Year 20 Year OG
Joined
Mar 2, 2002
Threads
50
Messages
1,612
Location
Duluth, Minnesota
Hey guys, hope this is a simple problem. I am able to receive but not transmit with my cb. When I power the mic the recipient just gets a loud "buzz" or "drone" sound and nothing else. Both cb and antenna are grounded to the battery. Also the power is direct. Could it be the mic causing the problems? It occurs when the truck is either running or off. Thanks in advance.
 
What is the SWR for the system? I'm guessing maxed out on the meter, but that's just a guess.

I'm also guessing you have a short somewhere - check the SWR to verify this and then start checking continuity in the antenna and coax. Once you rule out a short and confirm appropriate continuity, you can move to checking the mic and radio.

Of course, this course of action assumes you have neither an alternative radio that is confirmed to be working correctly, or alternative vehicle with installed antenna that is confirmed to be working correctly. If you have either, everything gets easier faster.

If you have an alternative vehicle with working antenna, remove the radio in the other vehicle and connect your CB and see what happens. If the same problem occurs, we at least know it is a problem with the radio and not the antenna or power line.

Likewise, if you have another CB radio that you have confirmed is working properly, connect it to the antenna in your cruiser and see if it has the same problem. If you have a short in your antenna, the SWR will still be maxed out.

To be safe, I don't recommend transmitting anything. Just briefly key the mic to determine SWR - don't talk or whistle. If your antenna is shorted, doing so could damage the radio as the transmitted power cannot 'get out.'

Good luck, and let us know what you find.
 
Well my mic worked fine in his rig. Not alot of time to devote to tracking this down right now. We quickly swapped radios in truck which didn't narrow it down much. His didn't work in mine either. I'm going to the guy I bought the radio from for some assistance next week. He was sure the antenna was okay. Want to confirm before sending the radio back to Cobra. Thanks for the advice. I'll let you know what happens.
 
alkarich said:
Well my mic worked fine in his rig. [snip] We quickly swapped radios in truck which didn't narrow it down much. His didn't work in mine either.
Click to expand...

Actually, that narrows it down a LOT. If your radio worked just fine in his truck, attached to his power supply and his antenna system (coax, antenna, mount) then your radio is not the problem. As further support, when you connected his radio to your truck power supply and antenna system (coax, antenna, mount) the other radio failed to work also.

This points squarely at your antenna system. It could be a cut or other damage to the coax (maybe when fishing it through the firewall or around the engine bay). Most likely however, is that you have a short in the system. Either when you soldered/connected the PL259 (if that is what you are using) or at the antenna side where it is mounted.

Either way, a quick SWR reading should help you figure this out. You didn't post the SWR reading - if you have access to an SWR meter, I highly recommend you use it.

Good luck!
 
Well at first it was just the mic that was swapped (mine worked in his rig). With the radios swapped (mine in his rig, his radio in mine) I no longer received transmissions as before and also could not send. So at this point does that point to the CB or the antenna? I'll be away til this Sunday when I plan on tackling this with a SWR meter with the guy who helped me install it originally. Thanks.

Miescha thanks for the help, you really do know alot about CB's.
 
Slomo had a similar issue that was due to a crossover situation. If the antenna connections, etc are all accessible, try wrapping all the metal with electrical tape to eliminate any crossover issues.
 
alkarich said:
Well at first it was just the mic that was swapped (mine worked in his rig). With the radios swapped (mine in his rig, his radio in mine) I no longer received transmissions as before and also could not send. So at this point does that point to the CB or the antenna? I'll be away til this Sunday when I plan on tackling this with a SWR meter with the guy who helped me install it originally. Thanks.

Miescha thanks for the help, you really do know alot about CB's.
Click to expand...

Uh, sorry I misunderstood. Well, check things with the SWR meter and let us know - then we can plan the attack from there. Try Brent's idea too.

I certainly do NOT know all that much about radios (CB, Ham or commercial) but I have worked my way through a LOT of problems, so I recognize some of the common issues and best approaches. However, several people here on mud DO know a lot about radio, Brent and Rusty for sure.
 
Okay here we go again. More definitive answers.

1. SWR readings from 1.2-1.5, not too bad.
2. Good continuity with the antenna.
3. With SWR meter hooked up my CB works (without it doesn't).
4. But a different CB (new from package, different model) using existing wiring worked. Able to receive and transmit to a handheld CB.

So I'm planning on contacting Cobra in the am. Any thoughts?
 
Well, the SWR readings certainly seem fine, but the radio still isn't working. I've seen the addition of the SWR meter change the transmission quality slightly, but not enough to make a non-working radio suddenly work. FWIW, the addition of the SWR meter and pigtail cable can affect transmission/receive quality b/c it lengthens the antenna (especially in a 1/2 wave antenna using the coax as a counterpoise for ground plane).

I still think there must be a cross-short somewhere - most likely in the coax connector. Here's a 'thinking out loud' idea: if the SWR meter is continuity separated, if the coax connector is shorted (keeping the radio from working normally) is it possible the addition of the SWR meter is correcting this, thereby allowing the radio to work properly?

Just thinking out loud. I guess we should wait for the new replacement radio to arrive.
 
Well got the new radio (18 WX ST II) yesterday and tried it today. Same results! Able to receive not transmit. Hooked up a magnetic mounted antenna to the hood and it worked fine with other existing wiring unchanged. This radio as opposed to the other radio (19 DX IV Compact) has the NOAA channels. Could something internally be causing this? The guy helping me thinks the NOAA channels run on an FM freq which may be causing this. I'll probably end up just keeping the mag mount. Mostly because of frustration with this. Any other thoughts? Thanks again.
 
Man, this sucks. I'm really sorry you're having so much trouble. This is exactly the kind of thing that turns people off to radio (CB, Ham or anything else).

It really is worth getting it resolved, as you really do need reliable communications on the trail (and elsewhere) and cell phones are just not reliable all the time.

If you are using the exact same coax with the mag mount, it is clearly your antenna and/or mount. Basically, the problem is somewhere after the point at which you disconnected the coax - leaving only the mount and antenna.

To rule out the mount, you could reconnect the coax and then swap the antenna. Likewise, you could change the mount and use the same antenna, but I find this takes more time.

I hope you get it worked out. If I were anywhere close I'd come by and help you figure it out.

Keep at it!
 
Hello Miescha, again thanks for the input. I agree on the importance of having a reliable way of communicating while on the trail.

So I still think it might be a combination of the style of radio and antenna location that is causing this issue.

Last week the existing wiring, antenna, coax worked with the different model cb. Nothing was changed just radios swapped.

By the way I should describe where my original antenna was mounted. I have a bull bar that at it's high point is a couple of inches below the hood level, on the bull bar is an 8274. The base of the antenna was at the high point of the bar (with a separate groung wire). The tip of the antenna was 3-4 inches above my rollcage. The antenna tested with good continuity.

The mag mount antenna came with a new already attached coax. It worked located on my hood and on the wheel well by the jump seat. But with the prior radio swap working I don't believe it to have been the coax or antenna.

So could it be the NOAA frequency causing this? Something in the "guts" of this style of radio?

Thanks again Miescha, Alan
 
Are you running any type of switch between the radio and the antenna or is it a straight connection from radio to antenna? Slomo had dual antennas on his set up and there was a ground issue in the switch causing his set up to not transmit.

Sounds like you have a straight shot set up tho. It's bizarre that one type of radio worked and both your old and replacement radio of a different brand don't. That doesn't make sense.

Any kinks, cuts etc in the coax?
 
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