Butternut HF9V, Инструкция по эксплуатации

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TECH NOTES—GROUND RADIAL SYSTEMS
a slightly elevated vertical with relatively few radials may be more effective than
a ground-level vertical operating over a larger number of radials if only because
the former is apt to be more in the clear. Resonant radial lengths for any band
may be calculated from the formula:
Figure 3 shows the basic ground plane system for elevated
verticals. Radials may slope downward as much as 45 degrees
without any significant effect on operation or performance.
Radials for different bands should be separated as much as
possible and the far end of each radial insulated from
supporting wires. Figure 4 shows a ground plane system that
uses four resonant radials for 40 meters, another set of four for
20 meters, and a third set for 10 meters. A separate set for
15 meters is not ordinarily required because the 40 meter
radials operate as resonant 3/4
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radials on that band. At the
lower heights the separate wires of this system may provide enough capacitance
to ground to permit low SWR operation on 80/75 meters as well, but it is probable
that at least one resonant radial will be required for low SWR on that band. It’s
important to note that cutting each conductor of rotator cable to a specific
frequency will not work unless you separate it, angling each conductor away for
most of its length because the longer ones will detune the shorter ones.
The 12-radial system of Figure 4 is a very good one, but it
requires at least 12 tie-off points. Butternut has developed a
multiband radial made of 300-ohm ribbon that resonates
simultaneously on 40, 20, 15 and 10 meters. Four such radials
offer essentially the same ground plane performance as the
system of Figure 4 but require only 4 supports. These multiband
radials plus additional wire for an 80 meter radial are available
separately (our STR-II kit) or as part of the Butternut roof
mounting kit (RMK-II).
There are times when physical restrictions will dictate the use
of fewer than four radials, and at least one manufacturer
recommends 2 radials per band, the radials for each band
running 180 degrees away from each other. A simpler (and no
doubt less effective) system is shown in Figure 5. Since only
one resonant radial is used per band the antenna will radiate
both vertically and horizontally polarized energy, and the pattern will not be
completely omnidirectional. For true ground plane action and predominantly
vertical polarization no fewer than three equally-spaced radials should be used.