Car speaker noise.

[WackyComputer]

So, a few weeks ago as I drove by a cop car, CB and squealing sounds came from my car speakers. My radio was off at the time.

Ever hear of such a thing?

[WackyComputer]

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[Kill-Switch]

What was the question again? Sorry I seem to be a little distracted ... .. .

[Player0]

It would take an extra special device to provide enough electrical power wirelessly to affect your speakers through the car door.

So, with that said, the power driving the speakers was the radio's amplifier. This would normally be off if the radio were.

However, if the volume was down or muted, than the amplifier may have been on with very little input signal.

It's extremely likely that the cop's radio had enough power to send a bit of an input signal to the otherwise dormant amp. The amp then reacted the same way it does when it's provided a minor signal from the radio... it amplified and played it through the speakers.

It's very common for a cell phone or other radio devices to generate enough interference to be heard on PA systems, computer speakers, etc.

This can only happen when the amp has power. It's possible that on in your car, the amplifier is NOT disabled when the radio is off. It probably sits there all day with no input signal, waiting to amplify something.

The transistor itself won't draw a lot of power if there is no input signal to amplify. It will draw SOME however, which means that radio is going to drain your battery dead if you don't run the alternator for a month or two. Or 6. It should be very very little power, maybe at around 0.6v or so.

It's an interesting find though.

[Synthohol]

or its alien cops.
i hope you have a foil hat.

[WackyComputer]

Just a baseball cap lined with foil. Got to make them think I'm not protected, it keeps me safe.