

Hams can legally run up to 1500 watts.  It is very unlikely, however,
that a ham would be running that kind of power from a car.  Ham rigs
for cars put out around 100 watts.  It is possible that a 100 watt
radio would cause interference to consumer electronic 100 feet 
away.  Most TVs, stereos, and VCRs have very poor RF shielding.
If you experience the problem frequently, it may be 
caused by a ham, CBer, or other radio operator in a base station
nearby.    The interference may have been caused by a radio 
transmitter used for other purposes, such as police, fire,
etc.  If you heard voices over your stereo, I think you are
correct in assuming that the source is an RF transmitter.

If you have frequent trouble, you may want to try the RF ferrite
chokes available at Radio Shack.  The interference is probably
being picked up by your speaker wires, and those chokes can
be installed on the wires very easily (without cutting them).
Good instructions are included with the chokes.
If that does not solve the problem, you may want to search your
neighborhood for a radio operator.  Look for antennas on the roof
or car.  Talk to him/her about your problem.  There are things
a radio operator can do to reduce interference.

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