Interference / noise elimination can be a test for how much money you want to spend and how deep you're willing to look. CB radios are AM and prone to noise. Here are some things you can try to eliminate or determine the source of the noise. Understand that there are only 2 ways for noise to enter the radio: power leads or antenna lead.
Connect the power leads directly to the battery - not the accessory terminal of the fuse block - nor "tap" into an existing 12 V power line you happen to find. Turn the radio on to an unused channel - it should be fairly static free. Turn the ignition key to the RUN position. It should still be clear - but if you hear a sudden spike of noise that lasts a few seconds before stopping, the static is likely to be coming from your fuel pump in your gas tank. The pump runs to pressurize the fuel lines to the fuel injectors when the key is turned to START. The Ford Explorer is notorious for this - but cab be reduced by following this link
. It may work for your car, too.
Turn the ignition key to start the engine and let the engine run at idle speed. Listen to the radio as you vary the RPM from idle to 1000 - 1500 and let settle to idle again. Popping sounds that keep time with the speed of the engine is likely yo be ignition noise. This is caused by the high voltage (10,000 + volts) ignition system that provides spark for combustion in the cylinders. You vehicle may have more than one location where spark occurs. The spark plugs, distributor cap, rotor and coil are the primary sources of ignition noise. Replace broken, cracked, or otherwise damaged components and change the wires and spark plugs to "radio resistor" types. If a rising and falling whine is heard, the source is likely the alternator.
If there was no change - disconnect the antenna from the connector at the back of the radio. If the sound magically goes away - the vehicle and radio power are filtered very well - the noise in entering via the antenna lead.
Install a "filter" on the radio power leads - as close to the radio as
possible. The power leads act like an "antenna" for all kinds of
under-hood noise sources and carry it right into the radio.
Install a "filter" on the radio power leads - as close to the radio as possible. Since the power leads act like an "antenna" for all kinds of under-hood noise sources and carry it right into the radio, they should be stopped before they enter the radio. A coil (called a "choke") inserted between the power source and the radio along with a capacitor between the 12V + lead and ground is an effective filter. These filters are commercially available
everywhere and also on eBay
If the noise is getting in the coax cable, make sure your antenna is well grounded. Resist the temptation to use a "mag mount" as the ground is poor if not non-existent. Some have had some luck using snap choke cores
but I haven't used them myself.
Lastly, don't expect to remove ALL the noise. You'd be the first to do so. Some methods work better than others. You can find a wealth of info by googling "CB Noise Filter" or "12V filter" (no quotes)
Please rate this if it was helpful - good luck!