Frank,

How about posting a summary of them, for my example in an earlier post (I
listed all the input values for Reg's program). I'd LOVE to have the data
for my measurement verification!.

If you need the my values I can send them to you for a run. I'd be very
excited to see what NEC-4 says, and use them to validate my measurements.

73,

Hasan,

I ran a sample model from Cebik's 2nd book, and compared it with results
from Reg's program. The antenna used in the example is a 160 m vertical,
with
four buried radials. The height of the vertical is 40 m, and the radial
lengths
are 40.95526 m. The diameter of the vertical section is 25 mm, and the
radials
2 mm. Ground Er = 20, and conductivity 30.3 mS/m (33 ohm-m). The radials
are buried 0.163821 m (0.001 WL). The test frequency is 1.83 MHz.
NEC 4 shows in input Z of 47.2 + j 14.44 ohms. Max gain 2.11 dBi at
17 degree elevation angle. At the moment I have not figured out how
to obtain the total radiated power from NEC, other than the numerical
integration of the normalized far field data. For a symmetrical pattern
this is fairly trivial using Excel. The model does not include copper
losses,
so this should be added for accuracy. Reg's program computes the
input impedance as 30.35 - j 53.1.

I think I have all the data for your antenna from your previous post. There
may be some difficulty in actually running it in NEC 4 with the parameters
you have provided. The depth of the radials is so small (1mm), in relation
to the wire diameter of 4 mm. Wire junctions must occur at Z = 0,
and the wire diameter must be less than the segment length, which
obviously cannot be met. Also segment length tapering would be
required in order to keep the number of segments at a minimum, and
avoid excessively long run times. In effect your radials are close enough
to be considered laying directly on the surface of the ground. Cebik
does imply this is acceptable in his book, but on his web site
states that NEC 4 becomes unstable with wires in the region of Z = 0.
I assume this also applies to wires below ground. Under certain
conditions wires can approach the ground to within 10^(-6) Lambda
(about 0.1 mm at 3.62 MHz). Based on these constraints I could
develop a model, which will probably be close enough.

73,

Frank