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Delay Line
The
DXE-RCA8C-1
unit has two delay line female F connectors marked DELAY. This connection
pair will require one specific length coaxial cable assembly with male F connectors acting as a
jumper between the two female F connectors.
If you intend to size your array for frequency coverage other than 80 and 160 meter operation, see
the section on “
Delay Line
”.
The
DX Engineering DXE-RCA8C-1
uses a time delay system, not a traditional phasing system.
The delay line length is dictated by array dimensions rather than operating frequency, which allows
for the use of a single delay line for optimum directivity over a very wide frequency range. This
results in phase being correct for a rearward null at any frequency.
The delay line cable can be neatly coiled in a 1-1/2 ft diameter coil. Support the weight of the coiled
cable by taping or securing it to the support pole or mast rather than allowing it to hang from the
connectors.
Optimizing the Array
To determine if the antenna system output level is the limiting factor, tune the receiver to the lowest
band at the quietest operating time. This is usually when propagation is poor but some signals are
heard. Disconnect the antenna and set the receiver to the narrowest selectivity you expect to use.
Receiver noise power is directly proportional to receiver bandwidth (going from 2.5 kHz selectivity
to 250 Hz selectivity reduces noise by 10 dB). Connecting the antenna should result in a noticeable
increase in noise. If so, the array signal level is sufficient and further optimization or amplification
may not be needed.
If the array is used on 160m or 80m and the array still lacks sensitivity, then the optional DX
Engineering
DXE-RPA
Receive Pre-Amplifier with high dynamic range will easily compensate for
low signal level. Using a pre-amplifier when sufficient signal is already present may result in
amplification of the noise along with the signal.
It is always best to use the least gain possible
.
Depending on conditions, a lesser pre-amplifier may be unable to handle the signals of a broadband
antenna, which can cause receiver overload. At times, strong signals require the use of an attenuator
or bypassing the preamplifier. However, the
DXE-RPA
has better dynamic range than most
receivers and can be used to compensate for a low array signal output, even in high signal locations.
Hint: Using a combination of the RPA antenna pre-amplifier AND receiver front-end
attenuation or RF gain reduction or both, can often provide the best improvement in
signal-to-noise for enhanced reception and ultimate low band DXing.
Summary of Contents for DXE-RCA8C-SYS-4P
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