"Roy Lewallen" wrote
Richard Fry wrote:
. . .
No, the BL&E paper (accurately) stated that 194.5 mV/m is the
theoretical maximum field possible at 1 mile for 1 kW radiated by a
perfect 1/4-wave monopole over a perfect ground plane. The peak
values they measured came very close, but never quite achieved that
value.

Can you explain why they very nearly accomplished this perfect ground
value even though the ground wave signal had to propagate one mile over
ground of finite conductivity?
___________________

BL&E made their surface-wave measurements 3/10 of a mile from their 3
MHz monopole transmit site.

MW ground loss for the surface wave across a path that short is low,
regardless of ground conductivity. This may be seen in the scan
linked below, which was taken from Terman's Radio Engineers Handbook,
1st Edition, page 681.

The scan doesn't show distances less than 1 mile, and the curves are
based on higher ground conductivity than BL&E had to work with -- but
an extrapolation of those curves to the BL&E conditions should
convince most reasonable readers of the conclusion in my paragraph
above.

The BL&E paper published in the Proceedings of the IRE states (page
771) "For each antenna height, 0.2 watt of power was fed into this
antenna, and the field intensity was measured at 0.3 of a mile. This
figure was then converted to a basis of a power of 1000 watts and a
distance of one mile."

So BL&E did not normalize their readings to account for ground loss
either at 3/10ths of a mile or one mile, but apparently they did
assume that the effect of the ground loss was the same at those two
distances. That error would not be large, however.

What do you think would have happened to the signal strength
if the mile of intervening ground had been replaced by a perfect
ground?

They would have measured 194.5 mV/m, referenced to 1 kW of radiated
power. As it was, they reported about 191 mV/m (max).

I'll look into the correspondence between EZNEC and FCC
predictions.

Thanks. That will be interesting.

http://i62.photobucket.com/albums/h8...sFrequency.jpg

RF