Ok it ain't 4x4 but it is a tech ?

I've got a humming noise comming from the CB only when the engine is running. still works and works pretty good too.

I've gotten 2 completely different answers to solve this.

1. plug wires- and I do have some cheapies. but the truck runs like a champ. I've done the whole look under the hood in the dark to see if there leaking and there not. (don't know how accurate that test really is though)

2. it ain't the wires it's the ground.

so help guy's what is it?
another question I just thought of is will this change my SWR I wouldn't think so but I'm an idiot.

alternator noise.. run down to radio shack and but a $5 noise supressor (sp?) . kill that hum right away.

oh yah forgot to mention that
I got one it helped a little. but not much. on the back of the noise suppresor it gave directions. something a bout if you unplug the ant. and you still here the niose thise product will NOT work for you but they don't say anything about what to use in that case.

Originally posted by 67FLAT4
oh yah forgot to mention that
I got one it helped a little. but not much. on the back of the noise suppresor it gave directions. something a bout if you unplug the ant. and you still here the niose thise product will NOT work for you but they don't say anything about what to use in that case.

If you unplug the ant and the noise goes away then you have a bad ground. Where is the ant attached to bumper on the frame? You may have a crappy cab to frame ground, or a bad ground on the CB. Recheck your ground and move it if necessary. Do not run the ground directly to the bat, you'll wind up with more noise.

Theres a number of different causes for noise on a CB.

Different causes will need different fixes.

Try unscrewing the antenna at the mount (if possible). If it goes away, the noise is being picked up by the antenna, and would indicate either spark plug noise, or interference from electric motors (EFI fuel pump, for example). Radio suppression wires will help the ignition noise (also a CB with a noise blanker (NB) circuit will be far less susceptible to spark plug noise (ANL circuits are not as effective).
A fuel pump motor will need a suppressor capacitor across its power leads at the motor housing.

If the noise is still present after undoing the ant, its coming through the power wires. In this case its best to run the positive wire (#14 gauge is good) directly to the battery. Ground the neg lead to the nearest body ground (a bolt holding the seat or steering column usually works good). Some say run the neg also to the battery, but I have not found a benefit from that, and its one more length of wire to lose power (voltage) through.

None of this will affect your ant SWR.

I didn't touch it last night but will try to make some time tonight.

I'm running a mech fuel pump so the pump thing is out. but I do have an MSD which I have also heard can cause this. simplie disconnecting the ant is so simple I would feel stupid not to try it. If it is being picked up by the ant. what is this NB circuit you talk about? New CB? or can it be added?

thanks

A Noise Blanker is a circuit that detects the impulse type bursts of ignition (spark) noise and cuts out the receiver for a millisecond during the pulse so as to block reception of it. Its very effective.

Most (if not all) radios have the ANL (Automatic Noise Limiter). Often it is not switchable, but is still there. This circuit works in the audio detection stages of the receiver. The NB circuit actually blocks the pulse at the ant. input of the receiver.

NB circuits usually are found (along with ANL) in radios priced $80 or so and higher. Many Cobra and Uniden CBs have it. It cannot be added to a radio that didn't come with it.

Hope that helps.

years ago one of the 4x4 mags had an article on wiring CB's. It suggested using a piece of Coax for the power.

Run the center conductor to the positive battery terminal, and and hook up the outer shielding to the neg terminal.

Then at the CB, use the center conductor for power, of course, but ground the CB to the dash, DO NOT use the shielding for the ground.

This shields the power leads from picking up most engine noise. I've wired mine this way since I read the article, and it seems to work pretty good. Provides good clean power for your CB.