CB Radio picking up engine noise..

Macdaddy4738

Macdaddy4738

Well-Known Member
Joined
Jun 1, 2005
When the Jeep is on that is.

From what Ive been reading, the only sure fire way to combat this is to have the radio running right to the battery?

Any other ways besides this?
 
Are you picking up a buzz from your fuel pump? Where is your antenna mounted? Are you grounded to the tub or frame?
 
there is a filter for this....
damn beer...
name escapes me. Go to radio Shack ask for it...like $7 last one I bought...
 
my antenna is mounted on a support for my rear bumper. The ground is to...some metal piece behind my dashboard near the glove compartment.

The buzz only comes on when I start the Jeep, otherwise there is relatively nothing.
 
That is the alternator's AC ripple on the DC coming in to the CB. You need a filter to smooth this out. Like stated above you can get them at Radioshack or even at the auto parts store. Generically called "noise filters". Most of them are basically capacitors that "fill in the gaps" in the DC. Between that and good solid grounds (run a separate wire to the frame/body if you have to) for both the CB and the antenna mount you should be able to reduce or eliminate all the noise.

For an analogy, lots of people are familiar with "caps" that people install for big stereo systems. When the bass hits it drops the voltage and makes lights and other things pulse, so they add a big capacitor (because it has a faster discharge rate than the battery). This is happening on a very small scale in almost all vehicles all the time, but only sensitive devices (like radios) are usually affected by it.

I had to add a filter to my Frontier to get my CB to shut up. I also found that when I replaced my cheapo Radioshack CB with a good one that the noise was basically eliminated.
 
Sorry to hi-jack a thread but:

I have issues with my radio too.
1st issue is for some reason it gets out well,...for a moment. If I talk over a few words the recipient doesn't hear everything I say
2nd issue is noise. Not from my engine, but from anyone with an electric fan that rides up behind me.
 
Before spending the money on the filter, try running both wires to the battery. Thats the right way to do it anyway.
THEN if needed install any filters.


Matt
 
The best way to wire it up is pos. and neg. wires run directly to the battery, and another seperate ground to the case of the radio. Then run another grounding strap or two from the body to the frame. A filter should be more of a last resort sort of thing.
 
Filters are the proverbial band-aid half-ass fix. Eliminate all the bad installation and vehicle fault factors first, then go to a filter if the radio is so inadequately designed that proper installation doesn't help.

Bad grounds and poor connections will definitely cause noise problems as well as other symptoms. Run the power wires to the battery with a fuse at the battery 12V+ connection. The advice to run a case ground at the radio is a good idea. That ensures that the braid of the antenna feedline isn't providing the ground. Make sure the body is well grounded to the frame, that the engine is grounded to the frame, and the battery itself has a good connection to the frame ground. All that effort will ensure that the body is properly grounded to the frame and the radio is well grounded, and that other things in the passenger compartment don't find their ground through the radio's circuitry and the ground at the radio.

Make sure the center conductor connections of the antenna feedline aren't touching ground anywhere. That'll make the transmitter go into self-protect shutdown in the better designed units, and can cause the cheaper units to blow the final amplifier outputs.

Make sure the antenna mount ground is actually a ground, and that the mount itself is properly assembled and isn't allowing the center conductor wire connections to be grounded.

PS: there's no such thing as a "pre-tuned" antenna. That's another urban legend. They're pre-tuned and tested to an ideal lab standard, but few, if any installations are "ideal." Each installation is different and no antenna can be "pre-tuned" to cover all applications and mounting configurations. That ain't saying you won't get lucky from time to time though.

PPS: No matter what you've heard otherwise, cutting the feedline cable to a certain length accomplishes nothing more than fooling a cheap SWR meter. That practice flies directly in the face of known antenna science and only reveals that there's another problem. Since I'm in the commercial two-way radio business, I carry an antenna analyzer in the gear on my truck and would be glad to help any of you with an antenna problem when we run across each other. That's at no charge, BTW, I'm not in the CB business. :)
 
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