AM interference from the engine?

[tochigi-fuji]

I've never had decent AM reception in my car either with the stock unit or my pioneer head unit. I always assumed it was because my antenna was half broken. My dad was driving my car the other day and noticed that with the engine off the AM reception is fine.

I've heard of intereference coming from the engine bay before, but what specifically would cause it? Plug wires?

The FM reception is fine btw.

[TypeG]

usually poor grounds, but it could be a lot of things. later.

[xfactortype1]

im assuming you have an amp. its probably alternator whine or ignition back-talk.
hopefully your using resistor plugs and rfi wires. trying checking grounds like type g said, but it maybe be from the multiple ground you have. for the radio, and amp i mean. you could go to wal-mart and get whats called a line loop eliminator. it like 10 bucks and removes the engine wine. ill see if i can find a pic.



link for noise article
http://www.f22parts.com/services_page.htm



regards x

[Dirty Harry]

Amplitude modulated radio is inherently flawed and very susceptible to any kind of RF interference whether it be from a spark gap or other devices. It is nearly impossible to get a 100% clean signal if you have lots of other equipment in the area (everything in your car). You can try using resistor type spark plugs and better wires, but naturally, you still have live spark gaps every time a cylinder fires because of the simple fact that your car has a distributor. A little plastic cap is not going to insulate against all the RF/EMI coming out of there, and therefore, you have your RPM-related noise on AM stations.

NOTE: Ground loop isolators only work for noise on FM stations. This noise may sound similar but is caused by a completely different reason than most AM radio noise.

[xfactortype1]

yeah..what he said.