DX Engineering DXE-RCA8C-SYS-4P, Manual

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transmit antennas less than 1/2 wavelength but more than 1/10 wavelength (on the lowest
frequency). Close spacing of any part of the array to transmitting antennas can be done, but will
impact overall receive array system performance. This is possible, provided the active units are
powered off at least 5 ms before transmitting. Sites without sufficient land area for proper spacing
should use the optional sequencer,
DXE-TVSU to ensure the correct transmit to receive switching.
Examples of Array Performance
The DXE-RCA8C eight circle array system occupies less space than phased Beverage arrays and is
much easier to install, is less conspicuous and operates over a wider frequency range with similar or
better performance.
The Eight Circle Array achieves an optimal pattern when the array has a
radius of .327-wavelength.
This is represented by this azimuth pattern
labeled as “.325-wavelength radius”, which shows the best combination
of a narrow front lobe and acceptable side lobes. This pattern is true for
any frequency from 500 kHz to 30 MHz for which the array is sized with
a radius of .327-wavelength. This pattern achieves the best Receiving
Directivity Factor (RDF), which is a figure that compares the forward-
lobe gain to the average gain of the antenna array in all directions,
including azimuth and elevation. More information about the rating of
receive antenna systems and Receive Directivity Factor are described in
“
ON4UN’s Low Band DXing ” by John Devoldere, available from DX
Engineering.
As shown by the patterns of
Figure 10 , an optimized 160 meter Eight Circle Array is not useable on
80 meters. That is why the best performing Receive Eight Circle is built as a mono-band array.
The ultimate low band receiving antenna would be two Eight Circle Arrays, one optimized for 80
meters built inside of the other optimized for 160 meters. Each is optimally sized for a .327-
wavelength radius, according to the dimensions in
Table 5 .
The DX Engineering Eight Circle Array offers better directivity than the Receive Four
Square. However, it requires more real estate to accomplish better directivity, which in turn
requires eight selectable directions to cover all directions properly.
Only a monoband Eight Circle Array may be installed with passive vertical elements or active
vertical elements, but a multi-band Eight Circle Array must be installed with Active Vertical
elements.