On Wed, 13 Apr 2005 15:35:16 -0600, Bill VanAlstyne, W5WVO wrote:
>I've read in a couple places lately -- maybe in ads, not sure -- that
>creating an "effective RF ground" (whatever that would imply at the
>wavelength in question) can reduce received noise in the antenna circuit,
The ground system only influences receive noise when 1) the ground system is
part of the antenna (as, for example, when it is part of counterpoise; or 2)
the ground system is somehow carrying noise current and therefore RADIATING
noise, in which case the antenna could pick it up like any other signal; 3) it
is part of the antenna (as, for example, radiation from a dipole bounce off the
earth and either add or subtract from the radiation direct from the antenna
depending on the relative phase at various elevation angles.
Let's get something straight: "ground" is not a magical "sump" into which noise
disappears. It IS an electrode to which lightning discharges.
It is very common for the downlead grounding a transformer on a noisy power
line to radiate noise. Thus, that "ground" wire makes noise worse! Let's say
that you add capacitors from each side of the power line to "ground." Those
caps will shove NOISE current into the ground conductor, and it will act as an
antenna.
Jim Brown K9YC
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