Brake booster noise on cb

installed a cobra 75 in a 17 OR last weekend. Everything works great accept the horrible noise when I hit the brakes every so often. Yes it’s grounded and powered straight to the battery. I rerouted the wiring moved grounds no difference. I’ve narrowed it down to the power lines not the antenna. Has anyone figured out a solution yet or had this problem? I saw the fj’s we’re having a similar problem saw a couple of fixes they did but hate to mess with brake booster wiring.

 

How much power does it draw? You need to isolate the power, the easiest way is with a 12v to 12v dc adapter / rector. Something like this, (I can’t comment on the quality, just first link I found)

miniDC 12V DC to DC Isolator for miniDSP 2x4 and 2x4 HD

https://www.amazon.com/miniDC-isolator-noisy-supply-environments/dp/B06Y39NMNY

 

try a ferrite choke. see if that helps.

 

It is common to have noise problems when you run a power wire all the way from a battery.

That long wire acts like an antenna and will pick up any noise being produced under the hood.

CB radios are AM and very prone to noise. Everything from the alternator to the wiper motors can generate noise.

The best solution is to go to an electronics store and buy the largest electrolytic capacitor (in micro farads) you can. Make sure it is rated for 25 volts.

Connect the positive side to the red wire as close as possible to the radio. Ground the negative side.

Capacitors only allow AC (noise) to pass. This configuration will ground the noise, allowing pure DC to pass.

One last note. Capacitors try to maintain a steady voltage in a circuit. Ferrite coils, as mentioned above, try to maintain a steady current. They should be mounted in series with the power wire and will do little to reduce noise.

 

where do you have it mounted?

i have mine mounted in my center console and just pull power right from the center console cigarette lighter.......no noise at all.

 

The antenna box is in the glove box. Did you wire a cigarette lighter adapter to it? I installed a kenwood rf choke today cut the noise to 50%. I may try a different filter that has a electrolytic capacitor as mentioned above. I’ll report back when I find what works best. Thanks for the responses.

 

Just an update. So if anyone has this issue the kenwood RF choke gets wired inline(red) as close to the antenna box as possible, you can cut the ground off and delete the clips as it won’t work with cobra 75 but make sure it’s in the right direction. Sorry no pics. I double checked that all my grounds were good. Tuned my antenna with an swr meter and now with the squelch adjusted properly and sound tracker on there is no noise. My range is short but I’m running a 2’ firestick so that’s a given.