AM comes in strong and clear with engine off but gives strong static with engine running, to the point it's unlistenable. FM works great. I just installed a new factory antennae and wire in an attempt to fix and it helped a little, but still bad. What else could it be?

 

Variable pitched noise/buzz, that changes with motor rpm?

How's your plug wires? Any kind of electrical interference will just washout an AM radio.

 

Wires are new 9mm Ford Racing along with new MSD coil and cap/rotor. Did it before the ignition upgrade also. I don't believe it really changes with rpm, but I haven't really left on very long like that. But clear and strong when engine is not running.

 

If your antenna lead is original it could be bad, check your grounds for your sound system. I put in a power line filter inline with the positive voltage connection to the stereo and it fixed 95% of static. Also I properly grounded the radio to the chassis on clean fresh metal, and I made sure my engine block ground was good. Also if you have a high power alternator you could be getting alternator whine. Mine got worse after replacing the 2g 65a with a 3g 130a.

 

Just replaced the antenna lead. I think I need to find a better ground, I used a ground in the factory radio harness. Which inline filter did you use?

 

Your local mobile stereo shop either will make one or has them in stock. Basically a torrodial transformer

 

i installed a jvc head unit,4 pioneer 4-way speakers and a rockford frosgate 4 channel amp in chip truck back in 2010-11.sounds super sharp and clean but after the amp install i got alternator whine.i installed this one here and it cured it:

but it's got a mixed bag of results.for the price i gambled and it payed off.don't hate me if it doesn't work or you too lol! like GJ says though,you can pick these up at like radio shack too.it's worth a try.

 

Oh yeah I totally forgot! If you use a USB phone charger it can pick up all sort of crap through the power system. Especially if you plug your phone into the AUX of your stereo while charging.

 

Yea, I did notice that as well when charging my Ipad.

 

Here's the kicker for me, when i tune into my favorite AM station, I get two stations at the same time. I hear one the main station and then the other garbled in the background.

I think its the radio. It's a digital one, so there is no in between manual adjustment.