corrosion diodes as noise source...

[Robert E. Seastrom]

Some of you will remember that Sandy poked around under the hood of my
little red pickup truck a couple of weeks ago with a battery powered
scope, looking for evidence as to the source of my alternator whine
problem (audible on both tx and rx on the 2m radio wired up directly
to the battery, changed speed with engine RPM).

We were fairly sure it wasn't the alternator, but noted heavy
corrosion on the positive terminal of the battery.  This is not the
first time I've had a corrosion problem there, and I decided to swap
out the battery.  I get varying stories on whether there is any
significance to corrosion on one terminal to the exclusion of the
other; my guess is that it's just that the seal at the post is shot
and the electrolyte is wicking up there.

Cleaned, swapped batteries.  Terminal cracked.  Replaced terminal.
All connections are clean, fresh, and tight...  and no more
"alternator whine".

                                        ---Rob