AM radio not working - interference?

[bhavinb]

Hi everyone,

Hoping someone can help me. I bought an MSP which had a modified audio system. The owner took that with him when he sold it and didn't return it to stock fully or properly. So I got left with a slightly messed audio system.

The Head Unit is an aftermarket Pioneer unit. But while FM seems to be working just fine, AM has some heavy static and interference that is proportional to the engine RPM...weird.
I'm guessing he didn't connect the antenna amplifier back properly...

Can anyone help me with some info on where they are and how I should debug this problem?

Thanks
-B

 

[rsvinylgraphics]

sorry but who actually listens to AM anymore?

 

[bhavinb]

LOL...I knew someone was gonna say that.
The best traffic reports are on this news station thats AM 680.
Can't stand sitting in traffic.....

 

[rsvinylgraphics]

LOL...I knew someone was gonna say that.
The best traffic reports are on this news station thats AM 680.
Can't stand sitting in traffic.....

ahh ok forgot about that

 

[chromal]

I'm not sure if that's indicative of an antenna problem, or just the pioneer's AM receiver more sensative to RF noise than the OEM head unit. Either way, it's *probably* noise on your car's DC bus. Amateur radio enthusiasts with mobile rigs often face similar problems. One strategy for mitigating this kind of noise is to install filter capacitors near the battery and/or alternator, but I've never performed this mod myself, so YMMV.

 

[haveahotcarl]

My bet is for a ground loop in the system or simply a bad ground. Now it could be your alternator going bad and what chromal mentioned, but ground loops are very common. If you Google "alternator whine" you will find loads of information on how to fix it, but I have a few easy things to try.

First, make sure the ground strap from your battery to car frame is not loose or overly corroded. Then you need to acquire a short length of wire, about 3 feet. Pull the head unit out but leave everything still plugged in and start your car and rock some AM tunes...I mean sweet talk radio... Take one end of the wire and connect it to the ground on the HU or to the chassis of the radio itself. Then, take the other end and touch it to any bare metal surface in the car. Try a couple of different spots and hopefully the noise will go away. If this doesn't work, reply with more on what accessories and stereo equipment is still in the car. This includes all aftermarket lights, gauges, amplifiers, etc. This will help me better understand the whole picture.

Good Luck!

 

[haveahotcarl]

My bet is for a ground loop in the system or simply a bad ground. Now it could be your alternator going bad and what chromal mentioned, but ground loops are very common. If you Google "alternator whine" you will find loads of information on how to fix it, but I have a few easy things to try.

First, make sure the ground strap from your battery to car frame is not loose or overly corroded. Then you need to acquire a short length of wire, about 3 feet. Pull the head unit out but leave everything still plugged in and start your car and rock some AM tunes...I mean sweet talk radio... Take one end of the wire and connect it to the ground on the HU or to the chassis of the radio itself. Then, take the other end and touch it to any bare metal surface in the car. Try a couple of different spots and hopefully the noise will go away. If this doesn't work, reply with more on what accessories and stereo equipment is still in the car. This includes all aftermarket lights, gauges, amplifiers, etc. This will help me better understand the whole picture.

Good Luck!

 

[bhavinb]

Hey guys,

Sorry for the late reply, I don't come online often.
Thanks for the advise. I'll need a good weather weekend to check all these things out.

Will report when I got something!