The surface or ground wave is the most important fraction of total
radiated power. The correct radiation pattern of a vertical antenna
shows maximum radiation along the ground. Angle of maximum radiation =
0 degrees.

When deducing efficiency, to omit power radiated along the ground from
the hemispherical integration will result in serious error.

( Efficiency by NEC4 ) / ( Efficiency by formula ) = 0.38

I can imagine other losses in addition to loss in the radials but to
have the other losses several times greater is a bit much. Where are
these large losses? Are they in the soil surface - the only other
candidate?
----
Reg.

Correct Reg, I had thought the modified RP card
considered ground wave, but it does not. I am working
on a combined integration including the surface wave,
which should provide a more accurate indication of
the overall efficiency. I will also attempt the
analysis of various lengths of radial wires.

Frank

Reg, with the antenna we have established as our test model:
All wires #14, monopole 9 m, 36 X 10m radials 25 mm below
ground. Ground parameters Er = 16, resistivity 150 ohm-m.
I have calculated the radiation efficiency including the surface
wave. What is interesting is that the surface wave contributes
very little at elevation angles over 10 degrees.

For 100 W input the total radiated power, not considering
the surface wave, is 31 W. When the surface wave is
included the total radiated power is 36 W.

Frank