(C) How many elevated radials are "just enough"...?
Depends on how many dB you want to throw away. If you can, do 12 to
16. 32 is the kill-the-loss, never-look-back number.
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The link below leads to a detailed post on this topic by William Culpepper,
a broadcast consulting engineer.
Here is a relevant quote from W. Culppeper's post:
"The result was an RMS value of the eight radials of 302.7 mV/m/kW at one
kilometer. This compares with the FCC Figure 8 value of 307.8 mV/m/kW for a
93 degree tower with 120 ninety degree buried radials, however, a tower 87.2
degrees (the height of the WPCI tower above the four horizontal radials) has
an FCC rated efficiency of 303.7 mV/m/kW, one mV/m more than our measured
value."
The system using four elevated radials produced an accurately measured field
that was 0.029 dB below the FCC theoretical field for the height of the
monopole above the elevated radials. Not much performance thrown away,
there!
http://lists.contesting.com/archives//html/Topband/2007-11/msg00248.html
RF
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Topband Reflector
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