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Cb interference with stereo
I recently installed a cobra 29 in my Ford Explorer. I understand the
previous owner had the radio "tuned". If I key the mike while my factory car stereo is on, I can hear it through the speakers. I called a cb shop and one guy claimed the interference wasn't because of the increased radio power, but rather interference through the car's factory amp. Does anyone have any insight on this? If this is true , would bypassing the factory amp and installing a new stereo cure this? Thanks in advance |
"econof" wrote in message news:dElpb.70518$ao4.195390@attbi_s51... I recently installed a cobra 29 in my Ford Explorer. I understand the previous owner had the radio "tuned". If I key the mike while my factory car stereo is on, I can hear it through the speakers. I called a cb shop and one guy claimed the interference wasn't because of the increased radio power, but rather interference through the car's factory amp. Does anyone have any insight on this? If this is true , would bypassing the factory amp and installing a new stereo cure this? Unlikely. I run both CB and much higher powered ham gear in both an explorer, and an expedition, no problem at all with the factory radio. Poor wiring or antenna work could be causing the problems. Any normal CB should not interfere with your car stereo at all. It's possible that a new stereo would be even worse. Have someone who knows their business, check for RF on the coax. There should be none. Check where the CB is taking it's power from. Ideally, you should run a separate feed to the battery. There's a convenient unused grommet under the carpeting, on the passenger side. |
"econof" wrote in message news:dElpb.70518$ao4.195390@attbi_s51...
I recently installed a cobra 29 in my Ford Explorer. I understand the previous owner had the radio "tuned". DUH. "Tuned" means some CB butcher clipped the harmonic filters out of the radio. If I key the mike while my factory car stereo is on, I can hear it through the speakers. What did you expect? |
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I have a 2000 Ford F-150 and it seems
to be a problem with Fords. I dont know that it is a much the amp picking up the radio signal or the speakers/wires. I have a Kenwood stereo, no amp, and a 6 CD changer....gets into it as much as the stock one did, whether it is On or Off.. I was told to try ferrite chokes on the speaker wires....as soon as i get the door panels off....one of these days! "Got RF?" |
"OZARK333" wrote in message ... I have a 2000 Ford F-150 and it seems to be a problem with Fords. I dont know that it is a much the amp picking up the radio signal or the speakers/wires. I have a Kenwood stereo, no amp, and a 6 CD changer....gets into it as much as the stock one did, whether it is On or Off.. The only RF problem I ever had with a ford, (since 87, when I started buying them) was rear window wipers kicking off when I used more than 80W on VHF with a rear mounted 5/8 wave. Never did figure that one out, had it in the escort, and the explorer. Haven't gone QRO on the expedition yet. "off" dosen't mean what it used to, these days. The stereo may still be powered, but in a low power state, like your VCR is, when it is "off".. OTOH, your RF may be rectified in the output transistors, and appearing across the speakers, as a really crude crystal radio. AM is probably the worst mode for this, Rectified FM ends up with very little audio component, none in the ideal case, though in the real world, you end up slope detecting one way or the other. I was told to try ferrite chokes on the speaker wires....as soon as i get the door panels off....one of these days! You'd want to put those ferrites as close to the radio as possible. The speakers aren't the problem, and your RF isn't going to get into the speakers themselves. The trick is to keep the RF out of the stereo. I'd also look at why you have so much RF in the passenger compartment, since this is the real root of the problem. Sounds like you've got a lot of current on the outside of the shield, which indicates problems on the antenna coupling, or maybe the shield isn't attached at the radio end? |
Dave VanHorn wrote in message ...
The only RF problem I ever had with a ford, (since 87, when I started buying them) was rear window wipers kicking off when I used more than 80W on VHF with a rear mounted 5/8 wave. Think yourself lucky, the UK police had an RF problem, I believe it was on Vauxhalls (GM)... When they used their radios, the engine would cut out - wonderful in a chase, when calling for assistance. Regards, Peter. |
Think yourself lucky, the UK police had an RF problem, I believe it was on Vauxhalls (GM)... When they used their radios, the engine would cut out - wonderful in a chase, when calling for assistance. That could be just a bit embarrasing. |
"econof" wrote in message news:dElpb.70518$ao4.195390@attbi_s51...
I recently installed a cobra 29 in my Ford Explorer. I understand the previous owner had the radio "tuned". If I key the mike while my factory car stereo is on, I can hear it through the speakers. I called a cb shop and one guy claimed the interference wasn't because of the increased radio power, but rather interference through the car's factory amp. Does anyone have any insight on this? If this is true , would bypassing the factory amp and installing a new stereo cure this? Thanks in advance 1) Try coiling up the excess speaker wire near the AM/FM radio and taping it together with tape. This will change the inductance of the wire leads and may choke off some of the RF coming down the speaker wire. If that does not work you may need purchase some ferrite beads or loops (Radio Shack carries them) and then wrap the speaker wire around it to get a higher value of inductance. 2) Also try coiling up the AM/FM coax as it enters the AM/FM radio. This will create an RF choke that will cut off "common mode" RF signals running up and down the outside shield of the coax. It will not affect the AM/FM radio signals you want coming down the inside of the coax. 3) Coil up the DC power leads coming in to the AM/FM radio at the radio. You may need a ferrite loop from Radio Shack to make this work as well. 4) Install a high pass filter in line with the AM/FM coax going to the AM/FM radio (available at Radio Shack). 5) Install a low pass filter in line with the CB coax. 6) Close to where your CB coax hooks to the CB antenna, coil up the coax in a loop to stop RF from running back down the outside of the coax and back to the radio. For 27 MHz (The CB Band) and RG-58 cable wind just over 4 feet of cable in to 8 turns and tape it together. For RG-8 use just over 6 feet of cable wound in to 8 turns and tape it together. 7) Some DC noise filters may have RF noise supression built in. Hope that helps, Night Ranger P.S. The information I gave you came out of ARRL's Radio Interference Handbook, and the ARRL antenna handbook. |
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