I'm getting high amounts of noise on my Cobra 75 WX ST CB radio when my engine is running and the RPMs are up. I've traced it back to the CB, and have determined it must be the connection to the battery. Can anyone spot anything obviously wrong right off the bat, or do I need to start ordering filters, etc.?

I haven't terminated the wires with ring connectors yet, as I set things up quickly one night in order to have the CB available the next day for a trail ride. Could it simply be that I just need to add the connectors, or is it going to be much more complicated?

By the way, the reason I believe the problem is with the CB, and not the coax or antenna, is because I hooked a friends CB up to my coax-antenna and powered it from one of the power outlet plugs in the dash. Very clean reception, and no noise feedback. I didn't use the dash power outlets because I wanted "clean power" straight from the battery.

SWR Readings: 1.2 on Channel 19, 1.5 on 1 and 40.

Thanks for any ideas.

 

Did you try running the ground off the body instead of the battery?

 

Any particular reason why you didn't ground to the frame instead of to the battery?

 

Yes, I did try a ground to the frame initially (but still inside the engine compartment). Since I had all the noise, I went to the battery since I read where some folks thought battery ground was preferable.

 

Can you describe the noise you are hearing?

 

I think it might be what some call "alternator whine". The higher the RPMs are, the louder the noise becomes. With engine running, but vehicle stopped, I can hear and transmit somewhat. As soon as the Jeep is in motion, noise becomes so loud that it washes everyone out.

 

I'm no expert but I am pretty sure it is your ground! I had that issue with a headunit I had once. Find a better ground and it should solve the problem. Maybe some others will chime in with other possibilities.

 

Thanks for the suggestion. I pulled the ground wire off the battery and it looks like it's partially melted. I had noticed this the first time when I disconnected it from the bolt I first used to ground to the body, but it wasn't as bad then.

Any suggestions as to what the problem may be? Too much resistance somewhere causing the ground to heat up (I'm just wildly speculating now)? What causes heat build-up like that in a ground wire?

 

Need to make a correction with respect to my statement above. After adding connectors to the CB wires hooked to the battery, I also grounded the antenna a bit more securely. When I re-tested with my Cobra 75, the noise was still present, so I tried my friend's CB again. This time I started the vehicle after we hooked everything up, and ran it around the parking lot a bit.

Bottom line: The noise was on his unit too, and it was connected through the power outlet plug on the dash.

Now what? Seems like there's noise in all my electrical circuitry. Is there something else I can try, or is it time to start buying filters?

 

I'm beginning to think the EMI may be coming from me now as I'm getting really fired up about this.
I grabbed the coax and crawled all over my JK checking ground to the antenna mount surface (Note: not the antenna stud). I'm grounded from front to back, top to bottom. I got continuity from bolts underneath the vehicle attached to the frame, from the tailgate latch, grounding points beneath the dash, etc., so I'm fairly certain the antenna ground is good.

I did drive around the neighborhood with the CB on (with static), and then unhooked the antenna coax. The CB basically went silent - no static, no reception, nothing (prior to pulling the coax I could hear some faint voices over the static). Not sure if this means anything or not.

Help please. I think I'm about to go under for the third time.