Strange Interference Issue

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RustyMetropolis

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Hi guys! LOVE this website! I use it for work at RadioShack all the time! Now for my question:

I drive a 2009 Toyota Tacoma. In the center of the dash, right below the radio, from left to right, I have a cigarette lighter, an aux imput jack for the radio, and a power port that I use for my Cobra radar detector. My scanner's a Pro-164, and whenever I plug the aux cord into the scanner, and then attach my dc power adapter, I get a terrible hum. I've tested it, after reading some other things here. I've tried it with the engine running, with the key in just the ON position, and I still get the hum. It's definitely in the power cord, because it goes away if I run on batteries and still use the aux cord. I've tried everything from RF snap on filters on both the power and aux cords, and still get the hum. The only thing I haven't done is replace the DC adapter. Any ideas? Thanks in advance for any help.
 

radiotrack1

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Sounds internal in the scanner causing a ground on the audio output.you can try reversing the polarity of the audio output jack. Cut the wire and put center on shield and shield on center.
 

jim202

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You might also try putting a capacitor in series with the audio output from the scanner. many times you will find a DC voltage on audio lines. Putting these connections to another unit that ties that line to a transformer or what ever to ground can cause all sorts of interesting problems.

I would try a cap of about the 1.0 uf value or so. anything smaller will not pass the low frequency audio. Going too high and you will loose all the highs in the audio.
 

NCFire11

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Every time I use a scanner, or my iPhone to my radio's AUX, while hooked up to the vehicle's power source, I get the alternator whine.
 

K4NRG

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Go to Radio Shack and pick up an Audio System Ground loop isolator Cat No 270-054A. You will need to purchase some audio adapters as well but this should solve your hum issues.

Edit: If you are crafty enough you may be able to permanently incorporate this into the vehicle behind the dash...
 
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