What might cause excessive static on my AM radio?

Dear Car Talk

Dear Car Talk | Mar 01, 2001

Dear Tom and Ray:

What would be the most likely cause of excessive static on the AM radio band in my truck? I can hear static popping at the same frequency as the engine rpm. The static speeds up or slows down along with the engine speed. How can I get rid of this static? --Tim

RAY: Well, we can suggest some very fine FM stations, Tim.

TOM: Actually, your problem is not AM or FM, it's RF. Your ignition system is creating radio frequency interference (RFI), and it's being picked up by your AM radio.

RAY: RFI usually comes from the alternator or old, leaky spark-plug wires, and an RFI filter usually solves the problem.

TOM: Just hobble on down to your local Radio Shack, or a similar establishment, and ask them for an automotive noise filter for your AM car radio. It costs about 20 bucks and attaches to your radio's power line.

RAY: If you can't or don't want to install the filter yourself, any reputable car-stereo establishment ought to be able to put one in for you. And while you're there, you can avail yourself of their "noise filter and 17-inch roof-mounted monster bass speakers" special. Good luck, Tim.

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