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Sizing the Array
If there are no space constraints, follow the dimensional recommendations in
Table 5
for excellent
performance.
Only a monoband array may be installed with passive verticals or Active Vertical elements,
but a multi-band Eight Circle Array must be installed with Active Vertical elements.
As demonstrated in the previous sections, an Eight Circle Array that is optimized for a certain band
will not yield useful results on the next higher frequency band. Using the Active Receive Verticals
or Active Matching Units you can obtain directional receiving performance on two or more bands,
the array must be sized for the highest frequency band. The Active Receive Vertical elements
provide the required 75Ω impedance across multiple bands in order to maintain pattern stability.
A monoband 160 meter optimized Eight Circle Array is sized by multiplying the free space
wavelength at 1.832 MHz of 537 feet/wavelength times the optimum pattern circle radius of 0.327
wavelength, which yields an optimal circle radius of 175.6 feet. This places the vertical elements
about one-quarter wavelength apart, 134.25 feet.
However, as shown by the patterns of
Figure 10
, an optimized 160 meter Eight Circle Array is not
useable on 80 meters. If the Eight Circle Array is intended to be used monoband on 80 meter, or if it
will be used on 80 and 160 meters, then the best choice for sizing the array is at the 3.800 MHz row
of
Table 5
. The free space wavelength at 3.803 MHz of 258.65 feet/wavelength is multiplied by the
optimum pattern circle radius of 0.327 wavelength, which yields an optimal circle radius of 84.58
feet. This places the vertical elements about one-quarter wavelength apart, 64.74 feet.
Antennas are spaced 45 degrees apart. Layout above is typical for North America with the default
switch control position (1) making the array point toward the North East.
Summary of Contents for DXE-RCA8C-SYS-4P
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