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A Special Application
The DX Engineering
DXE-RCA8B
Eight Circle Array phasing and switching system may
also be used as a unidirectional or bidirectional end-fire/broadside array with the installation
of only four vertical elements, using 1/10 to 1/4-wavelength endfire spacing in combination
with 1/4 to 3/4-wavelength broadside spacing.
This limited implementation is for the user who specifically wants a very directional receive
antenna system that is pointed only in one direction, without power required, similar to a
single direction, phased Beverage array. It would also be switchable to a second opposite
direction with DC power, similar to a very long Reversible Beverage.
However, this end-fire/broadside array alternative to building a phased Beverage array
requires a lot less space and a lot less maintenance! Contact DX Engineering for more details
on the use of the
DXE-RCA8B
for a four element system.
Receive Antennas – Gain and Efficiency
One popular misconception is that antenna gain pays equal dividends in receiving and transmitting.
While transmit to receive antenna gain reciprocity applies to changes in absolute signal levels, it
does not apply to signal-to-noise. Once external noise levels are slightly above receiver noise floor,
signal-to-noise ratio is almost entirely a function of antenna pattern. System loss or system gain is
no longer a factor, and excessive gain can actually hurt reception of weak signals.
Efficiency is not a major consideration in dedicated receiving systems. This allows application of
techniques that increase directivity in receive-only systems, techniques generally unworkable or
unacceptable in transmitting antennas. In a Multi-Multi contest station environment, passive receive
elements offer significantly greater dynamic range.
Site Selection
Site selection is important. Three major things upset the pattern and performance of an array. Phase
errors, element impedance errors, and improper spacing. This array’s phasing system uses a
combination of end-fire and broadside phasing. This array forms a clean stable pattern with high
directivity over wide bandwidth. Because of the stable, clean, narrow pattern in eight selectable
directions, this antenna is the ultimate in receiving.
Directing the antenna pattern away from noise sources or toward the desired signal path is the
primary benefit. Antenna gain is a secondary advantage. As frequency increases, the fixed array size
becomes electrically larger in terms of wavelength. The increased electrical spacing produces higher
sensitivity (average gain) even though front-to-rear ratio only changes slightly. On the low bands,
