[TowerTalk] Simulation of Mismatched Antennas
Tod Olson
tao@skypoint.com
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>
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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