Tony Meloche wrote:

Why would reception improve - and noise drop - when the chassis
ground to the receiver is removed? This is noticeable on SW, but *very*
noticeable on MW.

AC power in the US is at an extremely low frequency of 60
Hz, which has a wavelength of around 5000 kilometers! This
means it takes a 5000 km long length of wire before you see
just one full cycle. 360 degrees in 5000000 meters, or about
0.000072 degrees of phase shift per meter! The voltage at
all points along a 10 meter length of wire at 60 Hz is for
all intents and purposes, exactly the same at both ends, and
it's an excellent ground.

Not so at 10 Mhz (10,000,000 Hz), where the wavelength is
just 30 meters. You'll see a whole RF wave across only 30
meters of wire. 360 degrees in 30 meters is 12 degrees per
meter of phase shift. That means the voltage and current at
each end of the wire will be significantly different, and
it's NOT an excellent ground. In fact, it's more like a 1/3
wavelength antenna that's grounded on one end, than an RF
ground. **** poor ground, it is.

You didn't mention whether you live on the ground floor. If
not, you're already doomed for having a good quality
electrical ground at *RF* frequencies.

Also, your results are poor with the ground, probably
because AC power system noise is coming in through your
ground wire. At RF frequencies, an AC power ground may be
very poor, because a length of wire becomes an antenna, even
if one end is grounded. Once you have 20 or 30 feet of wire
before it goes to an actual earth ground, I think all bets
are off.

The best ground for an antenna system is probably the
shortest and most direct to earth, independent of and as far
away from noisy wiring as possible. In this case, it would
be better to ground the antenna and feed your signal in via
coax cable, than attempt to ground the receiver chassis.
(Unless it's an old tube radio with a screw terminal for the
ground. These may provide a measure of electrical safety.
But otherwise... avoid.)

Ground connection is to faceplate screw of a (verified) grounded 3-prong
outlet, the best grouond I can muster, at the moment. Should I try a
simple length of "counterpoise" wire as a ground?

Given how noisy AC wiring can be, it can't hurt to
experiment. Try running the counterpoise wire so it's as
low to the ground (or floor) as possible. It may well
outperform your AC "ground", which probably is feeding in
massive amounts of electrical noise directly into your
radio. If it turns out to work better one way over another,
don't argue with results. :-)

This, of course, is all my opinion. Please accept it as
such.

-- Ross





Tony

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