CB Radio

[bobcotkg]

My Superliner has over the years has come to let the CB talk over the AM FM radio. If you turn up the dynamike to get out, it squeals like mad, thru the AM FM speakers. The cab is grounded good. All new coax to the CB antenna. It does it with the "big radio" or my stock Cobra 29. It has gotten worse the past couple months. Wondering if anybody else has ran across this problem? It has been quite a pain in the ass messing around and have gotten nowhere.

Bob

[Green Dash]

I had this problem once in a Freightliner but I was slip-seating at the time, so the solution was to drive another truck.

With that not being an option, every situation like yours that I've heard of was a result of grounding or cable routing issues. The cb antenna may need to be grounded to the frame. Also, if the cb coax is routed along side the speaker wire, bleeding could result.

There are probably other causes of this, but those are 2 that I remember being told were common.

[bobcotkg]

Thanks,

The way I understand it is that the outside part of the coax is the ground. I know quite a few CB guys say the antenna must be grounde and what not, but Dad has an antenna that is not grounded on a pickup and it works very well.

Did some quizing of a couple friends today and they seem to think it has to do with the AMFM antenna being on the roof and cophasing, and the stronger one takes over..

In reality there seems there is more to CBs than just hooking up wires and tuning the antenna...

Bob

[theakerstwo]

Just for the fun of it disconnect the speakers and connect back backwards from what they were. Seems like back in the old cb days ther4e was a driver here had same thing.I am talking about am/fm speakers. glenn

[Green Dash]

Correction: I mistakenly said the antenna had to be grounded, but it's the MOUNT that needs to be grounded and not all vehicles require a seperate ground wire. I had a Wilson 2000 antenna mounted on the mirror arm of 3 R models I drove and all worked fine. Tried the same thing on a CH with similar mirrors and couldn't get a good ground. I then mounted it on the grab handle above the rear window and that solved the problem. I drive a Sterling now and when I asked my CB guy the best place to mount the antenna (got them newfangled mirrors) he said "on a different truck". I have it on the handle above the window with a wire running down to the exhaust bracket.

[41chevy]

Try a CB RADIO LOW PASS FILTER. Radio shack and other type stores carry them for about $15.00. It's a small unit you plug in between your cb radio and the antenna that reduces interference to nearby electrical devices. A low pass filter filters out signals that you do not want transmitted from your station. CB Radio is on 27 Mhz. Most Low Pass Filters filter out all signals above 50 Mhz. Cb Radio filters are used to combat RFIor Radio Frequency Interference, which is what you appear to have. Paul

[bubbamobilin]

I just experienced the same problem. I had to change AM/FM tuner a few weeks ago. The old one was 12 years old and finally just gave up. Ever since I installed the new tuner my CB bleeds through on the speakers and I cannot pick up any AM/FM stations but the Sirius satelite part works fine. If I hit the mute button on the radio before I talk on the CB it does not bleed through. I have not been able to correct my problems either.

[Lmackattack]

Does the same for me...just turn the volume down.

[Rob]

Try a CB RADIO LOW PASS FILTER. Radio shack and other type stores carry them for about $15.00. It's a small unit you plug in between your cb radio and the antenna that reduces interference to nearby electrical devices. A low pass filter filters out signals that you do not want transmitted from your station. CB Radio is on 27 Mhz. Most Low Pass Filters filter out all signals above 50 Mhz. Cb Radio filters are used to combat RFIor Radio Frequency Interference, which is what you appear to have. Paul

A band pass filter is actually a little better than a low pass but a bit more money. I'd look for a band pass that will pass anything from 25-30Mhz and reject all other frequencies outside of this envelope. This will allow for slight mistuning that is prevelant in production radios of the consumer electronics design.

Rob

[41chevy]

A band pass filter is actually a little better than a low pass but a bit more money. I'd look for a band pass that will pass anything from 25-30Mhz and reject all other frequencies outside of this envelope. This will allow for slight mistuning that is prevelant in production radios of the consumer electronics design.

Rob

Good point! I for got about the bpf. With the digital AM /FM radios it's generally a narrow band interference. Paul