Butternut HF9V, Инструкция по эксплуатации

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TECH NOTES—GROUND RADIAL SYSTEMS
spot, away from obstacles (including the MH or RV) that can interfere with
radiation from the antenna. The second is that of installing the beat possible
ground system beneath the antenna in order to minimize losses from r.f. currents
flowing in the earth below the antenna. Fortunately, the metal bodies of both MHs
and RVs can be used as highly conducting ground planes for vertical antennas in
exactly the same way that automobile bodies, etc., provide the ground system for
shorter vertical antennas for mobile operation. The metal body of an automobile,
MH or RV may be viewed as one plate of a capacitor. Since the surface area of
even a small automobile is quite large and in close proximity to the earth, its body
is tightly coupled to the earth below and may be considered simply as an
extension of the earth itself—a kind of hill as far as radio frequencies are
concerned, but one having higher conductivity than the earth itself. RVs and
especially MHs, having much greater surface area, will therefore provide a more
extensive and effective ground system than a large number of radial wires
occupying the same space as the MH or RV.
As in mobile installations, a vertical antenna may be mounted almost anywhere on
the body of the vehicle or MH and made to operate with reasonably low VSWR,
but it is generally considered that the best possible location for a mobile antenna is
in the middle of the roof of the vehicle, i.e., at the center of the vehicle's ground
plane and at a point where the antenna will not be in the "shadow" of any part of
the vehicle. It is not usually convenient, or even practical to install a relatively tall
vertical on the roof of an RV or MH for any number of reasons, so the next best
procedure would be to install a vertical antenna with its base at the same level as
the roof, preferably near the middle of one of the longer sides. The exact way in
which this may be done is a matter of convenience, but a short mast extending
from ground level to the roof of the MH and RV and placed alongside the building
or RV would provide a stable and sturdy support with a minimum of mounting
brackets and other modifications to the RV or MH. For portable operation such a
mast could simply be lashed alongside the RV with the base in a shallow hole in
the ground for additional support, and there would be no harm in extending the
mast a few inches above the roof level to permit attachment of ropes which could
be used to hold the mast firmly against the side of the vehicle and to prevent side
sway.
This system has been used successfully with various types of RVs, travel trailers
and even passenger automobiles during portable operation. For "L" shaped mobile
homes a vertical antenna should be placed in the corner of the "L" so that the
metal roof will provide groundplane coverage over 270 degrees.