writes:






Alternator noise is often caused by an electrical "ground loop," as
the engineers call it, and it's not related to the taildragger
groundloop some of us are familiar with. The alternator generates noise
even if all the diodes are working, and in some airplanes even if all
the filters are in place. If there's a bad ground anywhere in the
alternator or power supply circuitry or radio and intercom circuitry,
resistance forms at that point and the ground current seeks another
path for a portion of the load.


I'm the first person to suspect ground loops. Copper-Aluminum
connections are infamous for this; Al in general enjoys oxidizing
to make our lives miserable. Add the vibration of an aircraft...

[I've wondered a CAD-weld type connection to the frame
for the battery ground, but there are too many minuses...and
that's only one ground...of many.]

But there's a clue in this line:

In addition, increasing electrical load seems to make it worse.

as that points toward diodes. At low loads you can limp along. At
full load, that {waveform} hole gets to be really important.

But, in any case, while you have the alternator out; clean up the
grounds...



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