> if you know someone who is a mobile ham radio enthusiast, he should be able
> to give lots of hints/tips about silencing engine noise on car radios and
> speakers. also you can check at Radio Shack (or ARRL for books on how to
> do this). there are lots of simple cheap things to try first before you
> spend big bucks on interference kits.

Especially since when you apply these techniques you are basically stating
that "I basically understand my system has become a large antenna because
of some ground loop, therefore I'll try to lessen spark gap transmissions
in the local area instead of fixing the loop."

It's no good when someone pulls up next to you with some large engine
with dirty spark plugs and messes with your tunes.

Let me add to my earlier list:

  6) If you have multiple components, try to ground all of the components
     to the same spot, as they will all share grounds with one another
     causing hair loss when you want to trace the noise down. 

       a) One would think that running lines from all the components to
          the battery will suffice in this case, but that is only true
          if the battery is close by. Long wires have a inherent 
          resistance that is HIGHER than a chassis ground.

       b) Sometimes people try to get around this type of ground loop
          by cutting the ground line in the audio interconnects. This
          is not recommended. If you are willing to try to isolate
          your components, do it the right way, set up balanced 
          interconnects. (Not cheap, but worth it for good sound over
          long runs)

       c) Sometimes you can find components that have a "ground lift".
          This is rare and probably a bad idea (tm) in car audio.

  7) Avoid running audio signal cables parallel to power wires. Planning
     helps. Run the power lines down the left side of the vehicle, and
     the audio lines down the right. In a bus this is hard to do.

  8) When making joints, be sure to solder and seal the connections well,
     making it so you cannot pull it apart with your hands.

  9) Definitely put fuses on your power lines, close to the battery and
     for convenience again near the components... but never fuse the
     ground lines.

 10) If there is interest I will post the table of power carried versus
     recommended gauge of wire.

------------
Joshua R. Poulson, Systems Engineering, ADP Dealer Services, Portland, OR
(a car audio enthusiast from time to time... once an owner of the loudest
VW Fox in the world... 1140W RMS)