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Old July 13th 06, 01:26 PM posted to rec.audio.car
e-nigma
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Posts: 180
Default Audiovox Wired FM Modulator Whines


> wrote in message
oups.com...
> Just installed my second Audiovox FMM100A wired FM modulator. The first
> one had a high-frequency "whine" (like a carrier tone, but audible)
> even with no audio source feeding the box and with the car engine shut
> off. It's like taking a hearing test at the doctor's office with very
> high-pitched tones. Audiovox tech support said that shouldn't happen
> (the most dangerous words in technology: "it *should* work" followed
> closely by "that shouldn't happen") and advised me to return it. The
> second unit performs identically. It's not that I'm overly sensitive to
> high freqs; the rest of my family hears it, too.
>
> I've tried relocating the ground, feeding power from a separate
> battery, wrapping the loose wires separately, enclosing the whole
> package in foil and connecting that to ground with a capacitor to
> intercept stray RF, etc.
>
> The whine isn't as audible while driving, but it's loud enough to be
> annoying even with the car radio treble turned down a bit. Otherwise it
> works like a charm: when switched on, it routes the audio through the
> car speakers on one of two FM frequencies even if there's a strong
> station on that freq.
>
> Anyone else have this problem? And/or a fix?
>


I have seen this happen before with that unit.
If you unplug the RCA inputs to the modulator, is the sound still there or
does it go away?
If it goes away then the problem may be the source unit. It could also be
radiated in from the RCA cables.
The RCA cables may be running near Vehicles computer or other electrical
devise.
If you still have the whine when you unplug the RCA's then It would have to
be the modulator or the power source.


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