On Tue, 17 Feb 2009 15:03:41 +0000, Mike Harvey
wrote:

Thanks for the response. It could be a bad connection to the ground.
As previous stated and to further clarify, I usually keep a trickle
charger on the battery and when I first go flying the battery before
starting is 13.5 volts. and no noise on the radio. When I get back
the voltage is 12.5 or less and I get noise on the radio. I've had a
tech check out the antennas and no problems and com1 was recently
overhalled last year. Com2 does not experience any problems. I don't
have a generator but I don't know what type of alternator it is. Need
to look at the log books

Mike

The 13.5V initially, if accurate, is probably a consequence of having had
the battery on the charger. It should read 12.7V fully charged but that
also means with no loads or charging after about three hours. If it is
reading 13.5 and has been off the charger for a while, then your voltmeter
may be reading high. That being the case, your 12.5V may really be 11.7V
or lower which might be low enough to cause your problem.
--ron