Im a newbie to CBs, and Im having some trouble. Here is my setup, Cobra 75wxst, 3' Firestick, Firering coax, "L" type mount on tire carrier (no tire mounted). I checked the SWR and cant seem to get good results. On ch 1 Im at 2 and on 40 Im at 2.5. I have the mount grounded with a seperate wire from the mount bolt to the upper sub bolt, the one that goes to the roll bar. I used the "star" type washers, cleaned the paint off the mount where the bolt and wire are. The mount is alum if that matters. I used the CB a couple times yesterday on the trail, and when I beeped my horn, it seemed to come over the CB.....Is this a ground issue? Thanks for any help you can offer. I thought I did everything ok but obviously I screwed up somewhere

 

Run another ground wire from the antenna mount, 12awg preferably to the frame but I've seen it run into interior nuts with good results. Grab the coax and move it around with your hand inside the cab, does the swr change? If so, you have "common mode currents", or in laymans terms you're getting signal coming back down the outside of the coax, hence the need for another ground wire. Your coax is radiating, not feeding.

 

Are you saying that when you honked your horn it actually transmitted (with RF out the antenna) your horn through the CB? Were others able to hear a sound when you honked on their CBs?

Also, how is your CB power wired up? Are you going direct to battery for +/-?

 

when i beeped my horn it came through my speaker, not sure if anyone else heard it. power is right to the batt, ground on the cb unit itself is to the right footwell area where there are some other grounds. My antenna mount ground is 12 awg stranded from ant mount to upper sub stud, with star washer and nut holding it on

 

Tailgate antenna mounts are troublesome. Poor conductors and have to deal with hinges. You need a heavy braided ground strap for best results.

Something like this is what you are looking for...

 

I made sure the grounds were tight, metal scrapped off the mount, tried wiggling the antenna coax while hooked up to the SWR meter to see if it changed, it didnt, still best I can get is about 2 and 2.3, and the horn still comes over the CB......cant figure out what the hell I did wrong....

 

Horns use electrical contacts, much like a relay, to pull in and then release a diaphragm that make the audible noise. The contacts also make electrical noise that can radiate to your antenna, and be received as a radio signal. The electrical noise may also radiate through the vehicle wiring and directly into other electronic equipment. This is unlikely, but possible.

Remove the antenna connection to the CB and honk the horn. Hear the noise? If no, then the noise is radiated to the antenna and must be removed at the source. If you do still hear the noise then there are several approaches possible, none of which are certain to cure it. The noise suppression techniques are available on line. Some might even work. Search for them.

Just how often do you honk the horn while trying to copy and understand an incoming message?

Forget the running ground wire nonsense.

 

The horn coming over didnt bother me, I just thought it meant I screwed up and either had a bad ground issue or something else. I dont use the cb too much, nor the horn. I was more concerned with the SWR readings, not being able to get them down to 1.5. Thank you all for your help