Frank,

I don't understand Smith Charts.

But you can tell me what conclusions the charts lead you to believe
about the behaviour of a lossy transmission line of various lengths.

I am concerned with reducing the uncertainty of my program from the
information contained in the graphs of input impedance versus length
which I am now able to complete.

joke I don't suppose you would like to repeat the excercise using a
ground resistivity of 1000 ohm-metres. Or repeating at 20 MHz. joke
----
Reg.



"Frank's" wrote in message
news:1qOzg.181008$771.118115@edtnps89...

"Frank's" wrote in message
news:H6Mzg.180983$771.142858@edtnps89...

"Reg Edwards" wrote in message
...
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
======================================
Frank,

Very interesting!

I am plotting graphs of R and jX versus length of radial.

Joining up the dots I expect to see shallow sinewaves
superimposed on
fairly level mean values.

At present there is a definite shape of curve appearing in the
reactance values while the resistance values are still fairly
level.

As length increases I expect to see something similar happening
to the
resistance curve which seems to be in between peaks and troughs.

From now on it seems safe for you to increase length in
increments of
0.2 metres. There is no danger of missing peaks and troughs in
the
curves.

Please keep up the good work.
----
Reg

1.8 m -- Radial Z = , I have reached 7.4m, but there does not seem
any point in continuing. Let me know what you think. It does not
appear to be behaving as I would expect of a transmission line;
but then I have no experience of transmission lines immersed
in a lossy material.

Also note the jump in impedance at 5.6 m. I double checked the
result, and it appears to be correct.

2.8 m -- Radial Z = 67.5 + j 19.2
3.0 m -- Radial Z = 70.6 + j 25.9
3.2 m -- Radial Z = 74.7 + j 31.6
3.4 m -- Radial Z = 79.8 + j 36.0
3.6 m -- Radial Z = 85.5 + j 39.0
3.8 m -- Radial Z = 91.4 + j 40.4
4.0 m -- Radial Z = 97.1 + j 40.2
4.2 m -- Radial Z = 102.0 + j 38.6
4.4 m -- Radial Z = 105.9 + j 35.9
4.6 m -- Radial Z = 108.6 + j 32.7
4.8 m -- Radial Z = 110.1 + j 29.3
5.0 m -- Radial Z = 110.5 + j 26.1
5.2 m -- Radial Z = 110.1 + j 23.3
5.4 m -- Radial Z = 109.2 + j 17.2
5.6 m -- Radial Z = 107.9 + j 19.5
5.8 m -- Radial Z = 106.5 + j 18.4
6.0 m -- Radial Z = 105.1 + j 17.7
6.2 m -- Radial Z = 103.8 + j 17.5
6.4 m -- Radial Z = 102.7 + j 17.6
6.6 m -- Radial Z = 101.7 + j 17.9
6.8 m -- Radial Z = 101.0 + j 18.4
7.0 m -- Radial Z = 100.5 + j 19.0
7.2 m -- Radial Z = 100.2 + j 19.6
7.4 m -- Radial Z = 100.1 + j 20.2
.
.
8.0 m -- Radial Z = 100.5 + j 21.4
.
.
9.0 m -- Radial Z = 101.8 + j 21.7

These data are so close to the center of a Smith Chart
normalized to 101.6 + j 21. Not sure how you
normalize with a complex number, but assume it is
with the magnitude of Z.

Reg:

It seems that the Smith Chart must be normalized with a
complex number. As expected, with a very high loss
transmission line, the impedance rapidly spirals towards
the complex Zo. From the data it is not clear what is
really happening, but on the Smith Chart it becomes
very clear. The curve crosses the "Real" axis at: 2.8 m,
5.8 m, and about 9 m. At this point the data are so
close to the Smith Chart center that any more
results are irrelevant. Even without a Smith Chart,
normalization of the data will clearly reveal where the
quarter wave multiples are located.

Frank