Noise on new install...

[Wildfire]

Hi, I'm getting back into cb after being out of it for a number of years. I dusted off my old Cobra 29 and put it in my Jeep last week. I have a Wilson 4' flex on a Terraflex tail light antenna mount and am using mini 8 coax. I also use a mini 8 coax as my power line hooked up to the main power box (right off the battery).
I don't think I have problems with fuel pump noise, but I do have two types of noise in the system. First if engine noise which I assume means I need to get some grounding straps to reduce. The second is a static that is present all the time. It has no relationship to engine, fuel pump, or anything else in the vehicle. It's a pretty steady noise. I'm wondering if I have another grounding issue. The radio is mounted to a steel tube that runs on top of my roll bar, but it sits on top of the padding and is therefore electrically isolated from vehicle, so the radio mount is also isolated from the vehicle. Would grounding this help my noise issue? By the way, the antenna swr is app 1.4:1 so that seems to be within normal limits.
Bob

 

[mackmobile43]

Try this, disconnect the coax from the radio while the engine is running and see if the noise stops, most likely where you'll find your noise issue and if so clean all areas on the mount of paint where screws mount it to the vehicle and ditch the mini 8 as power lead and use some 12 or 10 awg primary wire.

And it never hurts to have a good radio chasis ground to the vehicle and then add a ground strap from the engine to the frame.

 

[Wildfire]

Thanks for the suggestion. I tried disconnecting the antenna coax from the radio and it has no effect on the noise.
Bob

 

[mackmobile43]

then the noise is coming across the power lead and or your radio has a fault due to it's age but I would bet it's the power lead at fault, try the suggestion.

 

[hotrod]

i agree with mack on changing the power leads.make sure your
nb/anl are on.if ya dont need alot of power cable ya can actually
get aweay with 14 gauge wire with just a cobra 29.

 

[Cajun Invader]

You can try adding an Electrolytic Capacitor to the inside of the radio at the power input.

I use between a 2200-4700uf 35 or 50V capacitor depending on the room allowed. Attach one leg to the negative and one to the positive.

Another source of noise could be from flourescent lights. If you are working around them turn them off. You would be suprised just how much noise they generate.

Light dimmers are also a cluprit. They are phase controlled and depending on the setting they create RF burst that sounds like buzzing or static on the radio.

One last thing it could be is a bad power line insulator or transformer near by especially if it's humid. They create an arch or corona discharge that will cause you interference.

I had the same problems you did. I was working on my vehicle at the shop and couldn't get the noise down. I messed with it for a few days and was getting frustrated. I drove the vehicle to the store and noticed the noise was gone but when I got back to the shop it was there again. Then I figured it out. Flourescent lighting and a dimmer switch on a ceiling fan.

Keep all of your coax and cables as short as possible. Use ferrite and ground straps and keep away from flourescent lighting.

Good Luck.

 

[Moleculo]

I have a jeep tj with a 4' firestick mounted similar to yours. The jeep is a vehicle that is notorious for noise that gets into radio equipment. I found ignition noise, fuel pump noise, and alternator whine. The fuel pump noise was the worst...it was just a constant loud static in mine. To get rid of it, you have to get underneath of the vehicle and get some .01 ceramic caps and jump them from the positive to negative wires right at the fuel pump. That means you're going to have to cut the wires probably. It also wouldn't hurt to wrap the wires around a snap on ferrite. You can get this stuff at Radio Shack and it's cheap. What I did is take some wire on the workbench, wrap it around a torroid as many times as I could, then attach a couple of caps. Do that before you get under the jeep. Then when you're under it you just have to cut the wires and splice this filter inline. This got rid of a ton of noise for me. You can also try bonding the hood, tailpipe, etc. with some wide ground strap.

Lastly, there's always the option of installing a DSP speaker to filter out the rest of the hash, but those are a couple hundred bucks.

 

[Cajun Invader]

Lastly, there's always the option of installing a DSP speaker to filter out the rest of the hash, but those are a couple hundred bucks.

DSP Speaker