NEC-LIST: The average gain test.

Good day,

In the process of studying the differences between the EX0
and EX5 source models, I discovered that I could tune the
APG (average power gain) with the number of segments in the
radials. I found that, for a given number of segments on
the vertical radiator, the APG passed through 1 with only a
small number of segments on the radials, 6 or 7. This only
happens for the EX0 source. The EX5 model stays stubbornly
below APG=1. I thought it would be interesting to compare
these results with a set of tests in which the radials have
the same segment length as the vertical. In all cases, the
objective is to find resonance. The results are pasted in
below.

The results for the equal-segment-length cases have a very
smooth behavior, with a resonant frequency moving down from
about 3.306 to about 3.3 MHz, segs/vertical going from 5 to
51. The APGs show a steady progress toward 1. The tuned
APG results show a rising resonant frequency from about 3.42
to about 3.56 MHz. In the first three cases, the APG is
closer to 1 than the corresponding equal-segment-length
case. Also, the APG changes faster with frequency in the
tuned cases.

I suspect that this shows that APG=1 is important, but not
as important as equal-segment-lengths at a junction.

Doug Miron
SUMMARY
4 m center-fed vertical in free space. 4 radials off each
end, 16 m long.
All wires 0.4 mm radius. No loss. NEC2 runs.
APG=Average Power Gain.

Equal-segment-length tests.

segs/. segs/ MHz Zin APG
vertical radial
5 20 3.3 1.58487-j 1.18728 1.00719
                      3.4 1.69053+j14.9628 1.00714

11 44 3.3 1.58990-j 0.74233 1.00401
                       3.4 1.69639+j15.3602 1.00397

21 84 3.3 1.59241-j 0.386261 1.00247
                        3.4 1.69928+j15.6852 1.00244

51 204 3.2 1.49152-j16.3062 1.00136
                         3.3 1.59433+j 0.0883 1.00134
                         3.4 1.70149+j16.1202 1.00131

Tuned APG tests.
5 6 3.4 1.69744 -j 3.14874 1.00067
                          3.5 1.80863+j14.3894 1.00035

11 6 3.4 1.69528-j11.3045 1.00064
                           3.5 1.80727+j 6.92428 1.0002

21 7 3.5 1.80641-j 1.46127 0.999366
                            3.6 1.92389+j17.2341 0.99877

51 7 3.5 1.80255-j13.4191 0.999479
                             3.6 1.92068+j 6.42150
0.998681

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