More static on static....(heavy on the prose)

[Joe Yakubik <75363.2524@compuserve.com>]

Not having heard Huw's static, I'll just assume it's a cousin to mine and has
the same general source.  Mine doesn't appear to be reception signal strength
related, but I suppose it could be, given a sufficiently strong signal/noise
ratio.  Auto gain control of the antenna amp circuit maybe, constant amp outout
under varying signal conditions = relatively constant volume.

Onto the side discussions:  Eric Fletcher wrote that the signal strength was
reduced by 70 dB due to antenna polarization patterns when Huw drove near the
antenna.  Dan Masi responded with "Bzzzzzt.  Nothing to do with polarization,
simply antenna transmission pattern  (lobes)."  I'll take the middle ground:
When you are very close to an antenna your received signal may be reduced, based
on all sorts of things.  However, I think that under most normal condition two
miles from an AM transmitter is probably right there in the juicy spot of
radiated power.  (Note the "normal conditions" and "probably").  BTDT (D for
"designed" in this case, way back when...)

As to "Faraday shielding not being affected by potential" (Geez, I love
buzzwords)  I quote "Optically isotropic substances, when exposed to a strong
magnetic field, rotate the plane of polarization of plane polarized light.  This
is called the Faraday effect"  Whoops, wrong thread.  I'll take this one over to
Scott and the headlights.  As an Electrical Engineer by education, and into a
whole 'nother field of electricity by training:  I know that Faraday shielding
exists, but I'll be damned if I can remember what it is, nor do I really care.
I want rid of my static.

Dan Masi's ideas on the rear defroster/antenna may apply to the cars (sedans)
with the antenna built into the wiring, but even here I think that the antenna
amp is powered solely by the skinny white wire from the radio.  There's a common
box with a filter, but power supplies are "separate".

I can unequivocally say a few things:  It is absolutely 100% NOT caused by any
AC interference from the alternator or via ignition noise.  The hours spent in
my garage with the motor off attest to this fact.

It is NOT caused by EM interference from the grid.  Dancing around my garage
with a 6m long coax cable connected to my radio did not, by itself, cure the
static.  It did go away when I disconnected the antenna and stuck a piece of
copper wire to the coax core, and touched the shield with my finger.  But it
also did this when I was right underneath the defroster.  It was unwieldy to try
this with the whip antenna, but a stubby $5.00 special antenna worked the same
way.

It is NOT caused by high current flow in the vicinity of the radio.  A few heavy
duty cables with alligator clips from the grid to the battery (other wires
disconnected) show this.

I have pretty much decided it is a ground problem, but I can't figure out in
which direction to go:

My old defunct Fuba antenna said hello to Mr. Dremel tool this weekend in some
exploratory surgery.  It only confirmed a few things:  these antennae are not
repairable, they're destroyed in the opening up.  They also use the chassis as
the ground for the amp and the antenna.  Two circuits, one common ground -- the
antenna circuit, and the amp both ground to the car through the base.  You can't
easily isolate them both from the car and still use them both.  

Here's my latest possible fix:  attempt to isolate the whole antenna base from
the chassis, and run a ground wire all the way back to the radio ground.  I
can't just cut the coax shield, 'cause then the static leaks through the amp
channel -- unless I unplug that, too, but then I might as well stick a coat
hanger on my roof.  The other choice would be to run the ground wire back to the
battery.  I've already tried wiring the defroster direct.  Those rascally
electrons would rather ride around on my antenna cable than take the direct
route back to the battery.

Joe Yakubik