measures wrote:
>? During the 1950s, the US Army discovered that HF only penetrates a few
>inches into moist soil The need for a long ground that hits the water
>table is yet another old wives's tale of ham radio. The lowest Z HF gnd
>is large, flat, and near the surface.
And an old wives tale of the commercial communication industry as well,
huh Rich?
Of course if the soil is "moist" there is no problem with the ground as
moist soil provides the lossy conductivity one needs. But what if the
soil isn't moist? Getting down to the ground water is the best way to
ensure that you hit "moist" soil, particularly in some parts of the US.
This is why the recommended grounding is with long, deep ground rods.
You never know the absolute condx of your soil.
73,
Jon
KE9NA
Rods driven into the ground have absolutely nothing to do with making
an RF counterpoise or RF "drain." Ground rods serve only one purpose,
and that is to protect your equipment from lightning damage.
Polyphaser produces a good book on the subject of grounding, and
shows how good engineering practice will pay off when the storms come
your way.
Ground radials, or a ground screen under an antenna system handle the
RF end of things at a radio station. Rich is correct; they may lay on top
of the ground, or be buried a few inches, it makes no difference. The
reason radials are buried is to make the landscape look better at the
antenna farm. Relying on ground rods to serve in place of a proper
RF ground sends valuable RF into the lossy earth instead of its intended
destination.
(((73)))
Phil, K5PC
--
FAQ on WWW: http://www.contesting.com/ampsfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|