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Car Forum / Driving, Maintenance, Tuning / Car Audio / October 200960 Hz noise on car radio from powerlines
I recently acquired a 1994 Dodge Caravan with a pioneer supertuner AM/FM radio. It has bad problems on an AM staion I listen to whenever I am near powerlines. There is a 60 Hz hum that modulates the audio causing bad distortion. I thought this would be a grounding problem, and have tried adding an additional temporary ground at either end of the antenna cable, with no effect. Can anyone offer any help in solving this? >I recently acquired a 1994 Dodge Caravan with a pioneer supertuner AM/FM radio. > [quoted text clipped - 6 lines] > >help in solving this? Is it hum or buzz. I'm thinking buzz. I don't think i ever encountered this, but power lines will emit noise. Is the noise all across the band ? A different type of antenna may help. I'm thinking a big loop on top of the roof. greg First off, Greg knows much more about EE matters than I so I defer any and all questions of a technical nature to him. HOWEVER, that being said, I DO know that your car's engine (alternator, sparg plugs, ect.and other accesories in your car) emit more EMI (electromagnetic interference) inside your car than your typical suburban power lines along side every residential rode. In my 25 years involved in car audio, I have NEVER heard of problems caused by your ordinary power cable. True, when I have gone near LARGE CURRENT bearing cable like from a damm or reactor to a substation I do encounter noise over my AM band. I really don't think there is anything you can do about that as the EMI just plain over-powers and distorts all AM signals. There's no way for your radio to discern what's an AM signal and what's EMI on the AM band, a little like going through an "EMI" tunnel. But those type of massive lines tend to be few and far between But again, I have NEVER heard of plain old suburban power cable causing EMI. There just isn't enough juice going through those wires to create the kind of interference your describing, unless, again, you live near VERY large current bearing cable. I'm curious, how did you deduce it was the power cable causing the interference? Are you sure that's the source? MOSFET > >I recently acquired a 1994 Dodge Caravan with a pioneer supertuner AM/FM radio. > > [quoted text clipped - 13 lines] > > greg The noise only occurs when I am driving near power lines. It varies as the lines nearby change. When there is no powerline close to the road, there is no problem. The distortion/modulation is bad enough at its worst to make to understanding the spoken word difficult. The problem depends entirely upon my location. Each time I drive by the same bad spot, the problem recurs. > First off, Greg knows much more about EE matters than I so I defer > any and all questions of a technical nature to him. [quoted text clipped - 47 lines] >> >> greg >The noise only occurs when I am driving near power lines. It varies as the > lines >nearby change. When there is no powerline close to the road, there is no >problem. The distortion/modulation is bad enough at its worst to make to >understanding the spoken word difficult. The problem depends entirely upon my >location. Each time I drive by the same bad spot, the problem recurs. You failed to fully describe the noise. Are you listening to weak stations. Take another portable AM radio and compare. Surprisingly, my Cavalier Am radio is decent. I was amazed how many stations came in during the daylight. Most of my after market radios have miserable AM performance. Mostly from poor engineering and internal digital trash. I think the analog tuners were the best. greg >> First off, Greg knows much more about EE matters than I so I defer >> any and all questions of a technical nature to him. [quoted text clipped - 47 lines] >>> >>> greg I am not sure how I can better describe the noise. The signal has an additional modulation by the 60 Hz, distorting the AM audio. You can hear the background 60 Hz, and the audio warbles with it. My previous car had no such response on its AM reception. The Seattle station that I hear it on (The only AM station I listen to) is not a particularly strong station, although I have heard it on a cheap portable radio when I was 280 miles east in Spokane WA. Bob >> The noise only occurs when I am driving near power lines. It varies >> as the lines [quoted text clipped - 68 lines] >>>> >>>> greg Well, OK, it deinately sounds like you have studied the problem and I suppose against all better judegment I am forced to agree with you that the interference is coming from power lines. Sooooooo...... The first thing we need to determine is whether the interference is effecting the radio directly. What I mean by this is if you were to disconnect the anntenna, would the problem still exist? If the answer is yes, you may just plain have a faulty HU. If the answer is no, then as Greg pointed out, you need to devise an anntena that, as best as possible, pulls in AM stations and rejects EMI. Honestly, I keep trying to think "out of the box" on this one as I have NEVER heard of such a problem occuring with your basic suburban side-of-the-road power cable. I keep trying to figure out if it is something else that is causing the interference when near a power wire. Greg is certainly on the right track in sugesting you try a small portable AM radio in your car and see if anything strange occurs. This is a shot in the dark, but perhaps you have yet another EMI source, perhaps originating in the electrical system of your car, and the presense of the small amout of EMI from power cables somehow pushes this interference "over the edge" and becomes audible. Again, just a guess. I know this sounds like a lot of work, but I might sugest just plain completely re-installing your HU. THere are a thousand things that may have gone wrong with the initial install causing the problem. I mean, a good quality aftermarket tuner, like the one you have, SHOULD NOT do this. I wish I had the answer and could tell you to change this to this, but again, this is a new problem for me. When I have had problems I couldn't erradicate, it's surprising how just re-installing the entire thing will often fix it. Other than that, I don't have any other advice other than possibly returning the HU as it sounds like it may be defective. Good luck, MOSFET > The noise only occurs when I am driving near power lines. It varies as the > lines nearby change. When there is no powerline close to the road, there [quoted text clipped - 54 lines] >>> >>> greg |
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