At 7:21 PM 2/17/97, rohre wrote:
>I strongly disagree with the person who said you should not worry about having
>1/4 wave radials, and to go with less length radials; unless you were putting
>out 120 radials!!
>
>RADIALS DO WORK, ESPECIALLY IF THEY ARE CUT TO RESONANT QUARTER WAVE lengths.
>Random lengths won't work as well, on given bands.
>
Without going into a lengthy discussion of the details I simply refer you,
in rebuttal, to "Radial Systems for Ground-Mounted Vertucal Antennas" by
Brian Edward, N2MF (QST June 1985) in which it is stated:
"For a given number of rdial wires, there is a corresponding
sufficient wire length, which is, suprisingly, independent of the earth
characteristics."
The author goes on to demonstrate that there is also an optimum number of
radials beyond which little advantage will be gained, and that number is
certainly not even close to 120.
In addition I would call your attention to an excellent reference from the
RSGB entitled "HF Antennas for All Locations" by Les Moxon, BSc, CEng,
MIEE, G6XN in which the theory of ground plane antennas is covered with
satisfaction. I quote:
"Having thus established that the resonant length 1/4w, far from
being mandatory, is the one to be avoided . . . " p.43, and, in another
chapter:
"This reasoning is supported by excellent results known to have
been achieved on the main DX bands using only short buried radials . . ."
p.173
I support the statement that elevated verticals benefit from resonant
radial systems*, however, when the antenna is ground mounted and intends to
use the earth as part of the antenna system, then there are some important
reasons to not make the radials resonant but rather to make them shorter
and numerous.
*See "Elevated Vertical Antenna Systems" by Al Chrisman, KB8I (QST August 1988).
Cheers,
Grover K7TP
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