March/April 2005 National Contest Journal has
the last part of a two-part article by K3LC. He used
Eznec Pro 4.0 with a double precision NEC-4
calculating engine. Much much data, but here's
a simplified conclusion:
Over very poor soil:
40 ground radials beats all elevated radials combinations
(up to 6 radials at 60' height). Absolute gain of 60 buried
radial system is about -0.9 dBi.
Over very good soil:
6 elevated radials up 10' beats 70 and fewer buried
radials. Absolute gain at that point is about +3.0
dBi. Just 3 radials at 60' up has absolute gain of
about 3.5 dBi. Raising radials from 10' up to 60'
up increases gain about 0.5 dBi (i.e. not really
worth it considering the difficulty of building a 60'
elevated Ground Plane).
Bottom line: Over poor soil, go with buried radials.
Over very good soil, go with elevated. The latter is
probably even more true for salt water. This has
been proven in practice by many expeditions using
just 2 elevated radials over salt water. For some
reason K3LC did not model the 2 elevated radial case
but it would have been interesting to have seen that.
Probably best to read the article yourself and
remember it is all based on modeling only with no
actual measurements.
73, Bill W4ZV
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