At 04:11 AM 10/8/99 -0700, measures wrote:
>
>>
>>I agree hundred percent of Rich's and Phil's opinions. A HF ground is not
>>necessary for yagi (dipole) or quad antennas on towers. This only needs a
>>good
>>lightning ground.
>>More important is a free area around the directional antenna. A moist soil
>>will improve the reflected signals.
>>
>On the other hand, moist soil also improves reflections that result in
>cancellation.
Nope to both.
"The effect of ground reflection on antenna performance is dramatic. The
ground immediately beneath the antenna affects the antenna resonant
frequency and efficiency. More significantly, the reflection of radiated
signals from the ground in the foreground of a Yagi antenna determines the
vertical radiation pattern of the antenna over ground. For a horizontal
antenna over flat (alluvial) ground, this results in a complete
cancellation of signal at the horizon caused by the efficient reflection
below the Brewster angle.
The reflection is from the conductive or dielectric discontinuity between
the air and the surface of the ground (giving effect to skin depth), not
from some magical underground water layer..."
-- Leeson, "Physical Design of Yagi Antennas," p. 10-1 ff.
And now, back to amps?
73, Pete Smith N4ZR
n4zr@contesting.com
Sometimes a tower is just a tower
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