Go back to program Radial_3 for a few minutes and insert our standard
inputs.

Set the number of radials equal to One.

Slowly vary length between 1 and 10 metres while observing Rin + jXin
of the radial system.

Vary length to find maxima and minima in the value of Rin. Max and
min are more pronounced at the shorter lengths due to lower
attenuation.

Remember, the radial ( transmission line ) is open-circuit at the
other end.

There is a minimum of Rin when the radial is 1/4-wave resonant at 2.4
metres.

There is a maximum of Rin when the radial is 1/2-wave resonant at 4.8
metres.

There is another minimum of Rin, but less prominent, when the radial
is 3/4-wave resonant at 7.3 metres.

As length and attenuation along the line increase, the variations of
Rin about its mean become smaller. Eventually, of course, it converges
on Ro, the characteristic impedance. ( Ro is also computed but
remains constant as length is varied.)

There would be a full-wave resonance at approximately 10 metres but it
is damped-down into the noise by the attenuation of about 20 dB at
that length.

Now, what I would like you to do is search for the maxima and and
minima in Rin, with their lengths. using NEC4. At some places you may
have to use increments of 0.1 metres.

If you find any max and minima the values of Rin + jXin will be
different from my program and the lengths at which they occur may also
differ. I would like to use the information to improve the accuracy
of my program on the assumption that NEC4 is more correct when
calculating buried radials.

( In this investigation, you may think it peculiar that lengths as
small as 0.1 metres should be significant at 8 MHz. This is due to
the very low velocity of propagation along buried radials. Program
Radial_3 estimates VF.)

Reg,

I have done some computations around a 2 m radial length. I noticed
that I had made an error in my previous calculation at exactly 2 m.

1.8 m -- Radial Z = 70.17 - j 24.1
1.9 m -- Radial Z = 68.5 - j 19.0
2.0 m -- Radial Z = 67.2 - j 14.2
2.1 m -- Radial Z = 66.2 - j 9.5
2.2 m -- Radial Z = 65.5 - j 5.0
2.3 m -- Radial Z = 65.1 - j 0.6
2.4 m -- Radial Z = 65.0 + j 3.6
2.5 m -- Radial Z = 65.2 + j 7.8
2.6 m -- Radial Z = 65.6 + j 11.7

I can keep going if you think that these are the results
you expected. I am tempted to continue, in steps of
0.1 m, and plotting the results on the Smith Chart.
I expect the data to rapidly spiral to the center of
a chart normalized at 101. 6 ohms.

Frank