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[TowerTalk] Simulation of Mismatched Antennas

To: <towertalk@contesting.com>
Subject: [TowerTalk] Simulation of Mismatched Antennas
From: tao@skypoint.com (Tod Olson)
Date: Tue, 1 Sep 1998 14:22:30 -0500
As a result of advancing age I seem to have lost sight of the
objective.

I looked at your computer data and compared your results with the
table in the ARRL Antenna Book (p24-13 of the 15th Edition)
showing total line attenuation loss as a function of SWR at the
load and loss in the line when matched to the load.

Really crude 'eyeballing' of the chart indicates a total loss of
1.5 dB for your run #1 and 4 dB for your run #2.

If I am calculating correctly run #1 shows 0 log(67.85/100)
= -1.68 dB (vs. my graph value of 1.5dB) and run #2 shows 10
log(35.1/100) = -4.5 dB (vs my graph value of 4 dB). At this
point I conclude that your program and the ARRL graphs seem to
agree. However, I have forgotten what the "argument" was if there
was one.

Did you prove something was in agreement or did you show that
something was not in agreement?

Tod, K0TO


-----Original Message-----
From: leewells@lexmark.com <leewells@lexmark.com>
To: towertalk@contesting.com <towertalk@contesting.com>
To: <towertalk@contesting.com>
Date: Tuesday, September 01, 1998 1:44 PM
Subject: [TowerTalk] Simulation of Mismatched Antennas



At K5GW's recommendation, I wrote a little program to simulate
line loss, reflections, etc.  The program will print a line each
time
the wave travels the length of the line.  It displays the amount
of power lost
in the line, and absorbed by the load.  Below are a couple of
runs
using Steve Best's numbers from his experiments.  The end values
are almost identical.  If anyone wants the C source code, let me
know and
I can provide it.

The programs assumes 100% of the power is reflected at the tuner
end.
The reflected power at the antenna is a function of SWR:

power refl coeff = ((SWR-1)/(SWR+1))^2


73
--Lee - KT4ZX

===== RUN 1 ======

Input Power: 100.00000 watts     SWR 1.32000 : 1     Line loss:
1.64000 db
Power Reflection Coeffecient (antenna to line) =     0.01902
Line loss coeffecient =     0.31451

Iter   direction     loss pwr      xfer_pwr     refl_pwr
total_xfer    total_loss
   1   to Ant        31.45118      67.24468      1.30414
67.24468      31.45118
   2   to Xmit        0.41017                    0.89397
67.24468      31.86134
   3   to Ant         0.28116       0.60115      0.01166
67.84583      32.14251
   4   to Xmit        0.00367                    0.00799
67.84583      32.14618
   5   to Ant         0.00251       0.00537      0.00010
67.85121      32.14869
   6   to Xmit        0.00003                    0.00007
67.85121      32.14872
   7   to Ant         0.00002       0.00005      0.00000
67.85125      32.14874
   8   to Xmit        0.00000                    0.00000
67.85125      32.14875
   9   to Ant         0.00000       0.00000      0.00000
67.85125      32.14875
  10   to Xmit        0.00000                    0.00000
67.85125      32.14875

Total power delivered to antenna is    67.85125 watts
Total power lost in line is    32.14875 watts


==================

===== RUN 2 ======

Input Power: 100.00000 watts     SWR 8.74000 : 1     Line loss:
1.64000 db
Power Reflection Coeffecient (antenna to line) =     0.63149
Line loss coeffecient =     0.31451

Iter   direction     loss pwr      xfer_pwr     refl_pwr
total_xfer    total_loss
   1   to Ant        31.45118      25.26117     43.28765
25.26117      31.45118
   2   to Xmit       13.61448                   29.67317
25.26117      45.06565
   3   to Ant         9.33256       7.49579     12.84482
32.75696      54.39822
   4   to Xmit        4.03985                    8.80497
32.75696      58.43806
   5   to Ant         2.76927       2.22424      3.81147
34.98120      61.20733
   6   to Xmit        1.19875                    2.61271
34.98120      62.40608
   7   to Ant         0.82173       0.66000      1.13098
35.64121      63.22781
   8   to Xmit        0.35571                    0.77528
35.64121      63.58352
<snip>
  36   to Xmit        0.00000                    0.00000
35.91968      64.08032

Total power delivered to antenna is    35.91968 watts
Total power lost in line is    64.08032 watts


==================

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