ViaSat 8116 Series, Инструкция по установке и эксплуатации

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OPERATION
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a. The first nulls to each side of the main beam will become deeper
and eventually bottom out at some level (see Figure 5-1). This
level varies depending on the antenna, but should be equal to or
greater than 10 dB below the level of the first sidelobe. The
deepest null in the H-plane sometimes occurs at a different
subreflector position than in the E-plane. In this case, the
subreflector should be set at a compromise position between the
two planes (i.e., E-plane null depth approximately equals the H-
plane null depth).
b. The signal level of the main beam will also increase as the
subreflector is moved closer to the focal position. The power
meter can be used to monitor this change. The main signal level
will peak at the antenna focus; however, this change will not be
as sensitive as the change in the null depths. Peak main beam
signal level and minimum first null depths should coincide for
the best subreflector position.
c. As the subreflector is adjusted toward the optimum focal
position, the first sidelobe levels should decrease and remain
symmetrical within 2 dB. The minimum sidelobe level will
occur approximately at the same subreflector position as the
highest signal level and lowest nulls. Should the sidelobes
become asymmetrical (greater than 2 dB), a small tilt and/or
lateral adjustment may be required. It is recommended that after
each adjustment of the subreflector, the antenna azimuth and
elevation adjustments be re-peaked to compensate for any beam
steering due to axial misalignment.
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42S183D
SERIES 8116/8118 16-/18-METER EARTH STATION ANTENNA
5-3