Perhaps I should have said there is only a very small benefit
to having more than 15 radials IF they are equal or less than
0.125 WL long.
THE definitive work on radial systems was published in the
JUNE 1937 (yes 1937) issue of the Proceedings of the IRE
by Brown, Lewis, and Epstein entitled "Ground Systems
as a Factor in Antenna Efficiency". See figure 33 for plots
of Field Intensity at 1 mile for radials 0.137 WL long vs
antenna height for 2, 15, 30, 60, and 113 radials.
A more recent article entitled "Radial Systems for Ground-
Mounted Vertical Antennas" was published in QST for
JUNE 1985. The plots are from NEC computer models.
I suspect this is the basis for the HyGain table.
There was considerable discussion on this topic on
TowerTalk some time ago and should be available
in the ARCHIVES on Contesting.com
Bottom Line: Once the ENDS of the radials are within
0.025 to 0.05 WL to each other, there is little benefit
in adding more radials. Naturally the longer the radials,
more radials are needed to meet this requirement.
(I hope I remembered the right numbers here).
On Sat, 28 Sep 2002 Chris BONDE <firstname.lastname@example.org> writes:
> At 04:59 PM 2002-09-26 -0600, email@example.com wrote:
> >YES. IF you can get 1/4 WL (or more) then 30 to 60 radials is
> >beneficial. IF you are limited to 1/8 WL long radials, there is
> >virtually NO benefit above 15 radials.
> >Tom N4KG
> OK then please explain why hy-gain in their manual for the 14AVQ has
> a table for optimum ground system configurations as
> radials 16 24 36 60
> 90 120
> lengthin wl 0.1 0.125 0.15 0.2 0,25
> feed point impedance 52 46 43 40 37 35
> radial ends buried (?) Y Y Y N N
> Which to me states, if longer radials, then need more, impedance
> goes down
> and power goes up or if more radials need more etc.
> Just trying to figure out these things.
> Chris opr VE7HCB
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