"Richard Fry" wrote in message
...
"Walter Maxwell" wrote:
When reviewing these data, please keep in mind that as the field strength
approaches 194.5 mv/meter the effective ground is approaching perfect ground,
which means that the conductivity of the ground in which the radials are
planted is irrelevant, only the ground external to the radial system is
relevant with respect to conductivity.

BL&E measured the groundwave field strength generated by a 200 milliwatt
carrier 0.3 miles from a vertical radiator. This value was converted to
equivalent field for 1 kW of radiated power at a distance of 1 mile. With
this technique, and with 113 each 0.412-wave radials, they found that their
measured/converted field was less than 0.1124 dB below the theoretical value
for it over a perfect ground plane. These results demonstrate that the
consideration of ground conductivity during this study over this short path
was unnecessary (REG, please note).

It should also be kept in mind that the energy in the EM fields surrounding
the vertical radiator diminishes with distance from the radiator. Thus the
displacement currents entering the ground diminish proportionately with
distance. Consequently, there is a distance from the radiator after which the
currents become too small to be significant to the conservation of power
radiated. This fact determines the maximum length of the radials necessary to
reach the point where the law of diminishing returns prevails. The
measurements reported in the BLE paper show this distance to be between 0.4
and 0.5 wavelengths.

And that was for 113 radials. If only a few radials are used, BL&E report
that it is pointless to extend them that far.

RF

Correct on both counts, Richard, thanks for reminding Reg, I forgot to. Did I
mention that I had the privilege of working at Brown's RCA antenna lab along
side Epstein for several years? Bob Lewis had left RCA when I arrived, but I
knew him later as a ham, W2EBS.

Walt, W2DU