CB help please!

[Clark White]

So a friend of mine is having serious problems with his CB. When ever he Tx's, all I or anyone else can hear is a loud squeal (kinda like when someone turns the mike up too high at a concert, etc). We have tryed turning his mic gain down, but that does nothing (still squeals with the gain ALL the way down). We have changed his mic, changed the CB it's self, put the power to the bat and ground to the common ground on the firewall (along with a few other places we've tryed), replaced his coax (notes on this later), and replaced his antenna. When we replaced his coax the first time, we used my old 9', which fixed the problem, but wasn't long enough to be routed properly (done for trouble shooting purposes, and it had to be run along the side of the truck and across his seat to reach). Today, he put a 20' coax on and the problem returned, but when we went back to the 9' it no longer fixed the problem. SOMETIMES, he is able to get it to work properly, but the mic gain is not even a hair above minimum (off), and if you even LOOK at it, it moves too high and the squeal returns. I think that is about everything we have done so far. Tomorrow I want to run some more check with the multi meter on the antenna ground just to make sure that is all as it should be, but I'm pretty sure that is all good. ANY ideas of what could POSSIBLY cause this would be greatly appreciated!! Our minds are about turned to mush :drool: after multiple days of swapping parts back and forth only to have it squeal again

Thanks!!
Clark

Additional info: We are using Midland 77-115, he has a Wilson Firestick, I have a Radio Shack whip. Could it be the mount on his truck? That is the only thing that HASN'T been replaced, but ground through it is good.

AAAAHHHHHHHHHHHH!!!!!!!!!

 

[TJVach]

Alright this might sound crazy, but have you tuned your antenna to your cb? Having a mismatched antenna can cause all sorts of crazy problems. The multimeter idea is a good one to determine if you have a good ground. Other than that I'm stumped.

 

[Clark White]

Alright this might sound crazy, but have you tuned your antenna to your cb? Having a mismatched antenna can cause all sorts of crazy problems. The multimeter idea is a good one to determine if you have a good ground. Other than that I'm stumped.

Yep, we tuned it today at the same time as we put the 20' coax on, and his antenna was at about 1.3 SWR.

 

[LC/LR4Life]

Swapped out radios?

 

[4RunAmok]

Heh, easy fix would be get licensed, and get a good Yaesu 2800 2M radio. CB bites compared to 2M. Was able to hit and talk on a repeater in Blythe, 200 miles away from my location with my Yaesu and a roof mounted NMO mount Larsen antenna.

 

[DaveInDenver]

It's probably not mic feedback, so changing the mic gain is probably not the root of the problem. I've seen this a couple of times over the years. Both times it was related to the antenna and coax. Once the coax had been closed in a door and flattened and the other time the ground at the antenna mount was very poor because the screws holding the mount on had rusted.

My recommendation would be to replace the coax with known good stuff, replace the PL-259 connector at the radio and rework the antenna mount connection if it's not done from the factory. Then make absolutely sure that the mount (if it's a hard mount, screwed down into clean metal in particular) and radio are both well grounded to the truck.

 

[gary in ohio]

So a friend of mine is having serious problems with his CB. When ever he Tx's, all I or anyone else can hear is a loud squeal (kinda like when someone turns the mike up too high at a concert, etc). We have tryed turning his mic gain down, but that does nothing (still squeals with the gain ALL the way down). We have changed his mic, changed the CB it's self, put the power to the bat and ground to the common ground on the firewall (along with a few other places we've tryed), replaced his coax (notes on this later), and replaced his antenna.

How close are the two CB when your doing your testing. Since you have changed out the entire system, it may be operational issues. Squeal's are typically mic issues, but if you have changed radio that would be ruled out.


Are you parking vehicles next to each other when doing the test? YOu may just be overloading each other's radios. What if you swap radio's your for his, does the problem follow the radio or stay with the vehicle?

 

[bmonday]

I wonder if the antenna connector on the radio is broken inside. Sometimes the solder breaks loose and works intermittently. This would explain why your 9' cable worked before and not now. Might try wiggling the connector on the back of the radio a few times and see if it fixes the problem. If it does, it's time for a new radio.

BMonday