AOR AR8000, Руководство по эксплуатации

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AR8000 operating manual
110
Coaxial cables
When constructing dipole aerials or connecting VHF aerials 50 OHM coaxial
cable should be used. For shortwave or short runs of VHF URM43, URM76
or RG58U is ideal, for longer runs of VHF-UHF feeder it may be worth
considering a heavier URM67 or RG213 (or better!).
ATU & preselectors
Aerial tuning units (ATU) may improve the shortwave section of a wide
range receiver by rejecting unwanted signals and only allowing a specific band
of frequencies through. These ATUs are normally constructed in small boxes
with about 3 controls on the front. The disadvantage is the need to constantly
retune the ATU when changing frequency. An ATU of this nature is “passive”,
this means that no power is required to operate the ATU and no extra
circuit-noise is introduced into the receiver.
Loop Aerials
Short wave desktop loop aerials have the advantage of small
size (such as the AOR LA320). They too have tuning controls
to reject unwanted signals. As the loop is within easy reach of
the operator it can be rotated to provide directivity. They can
be particularly useful for DX’ing the lower bands.
Generally speaking they offer excellent portability but cannot compare on the
higher bands with a well sighted long wire aerial.
Active aerials
Active aerials are normally quite compact (AOR WA7000)
and combine a wide coverage aerial (30 kHz - 2 GHz) with
a preamplifier mounted within the aerial its-self. They
require power to enable them to operate. Not all designs
allow you to switch the preamplifier off although some have
a gain control.
As with loop aerials they tend to provide good results on the lower bands when
compared to poorly sighted short’ish wire aerials. Overload can be a problem
on the busy 7 and 9 MHz bands. If you have a small garden space, an active
aerial may be worth considering.
Discone
For wide coverage in the VHF-UHF bands a compromise has
to be met and the most popular aerial is a discone (AOR
DA3000). Their appearance is like a large spider or umbrella
without the covering material, the better models have about 16
elements.