Topband: Radial length

Jim Monahan K1PX at
Thu Nov 30 17:59:27 EST 2006

Al Christman, K3LC wrote a comprehensive article in the March/April 2004
issue of NCJ entitled:

"Maximum-Gain Radial Ground Systems for Vertical Antennas"

Data was derived from using NEC4 with #16 wire just below the
surface and a 1/4 wave vertical element.

It covers 160, 80 and 40 meters and the optimum number of radials
and lengths for total wire length versus very poor, average and
very good soil conditions with graphs and data points.

For example, from Table VII which is entitled:

Optimum number and length of radials for a vertical antenna on 160 meters
(1.835 MHz) operating over average soil (conductivity = .005 Siemens/meter
and relative permittivity=13).

Total wire    Optimum number of radials    Optimum length of radials     Peak gain
in ft.           in ft.                                 in ft.                                in dBi.

500            11-12                                45.45-41.67                      .11 dBi
1000           17-18                               58.82-55.56                      .38 dBi
2000           23-28                               86.96-71.43                      .63 dBi
4000           32-40                               125.00-100.00                   .89 dBi
8000           45-55                               177.78-145.45                   1.17 dBi
16,000         76                                   210.53                              1.48 dBi
32,000         99-122                             323.23-262.30                   1.75 dBi

Previous articles are available at the NCJ website but I couldn't open this particular
one for reference.<>

The link may have to be typed manually since my e-mail has an HTML tag.

73, Jim, K1PX

K1PX at<mailto:K1PX at>

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