I'm continuing my investigation into the problem of the Pegasus displaying
high (2.0:1 or greater) SWR readings when the PT-11 tuner believes that the
antenna is tuned.
Further to my earlier posting and encouraged by some comments received in
reply, I have removed the PT-11 tuner from my Pegasus and rerun my tests.
The results clearly show that on 18 MHz and above, the tuner has an adverse
affect on the Pegasus SWR reading. The results also tend to disprove one of
the explanations about the problem - that is, that the Pegasus SWR system is
not reporting proper values. From the data, the Pegasus SWR readings track
very well with the SWR.
Test description: I a manual antenna tuner to create a load of known SWRs
(1.0, 1.2, 1.5, 2.0 and 3.0) at frequencies at the middle of each ham band
160m - 10m. The SWR was measured and the tuner was set using an MFJ 259B
antenna analyzer. I than ran the max power from the Pegasus into this load
and recorded the forward and reflected power as indicated, and calculated
the SWR. The Pegasus and MFJ 259B were connected on the two sides of a 2
position coax switch to facility switching back and forth. The tuner was
connected to the common position of the switch (just like using the switch
to drive two different rigs, with the Pegasus being one rig and the MFJ 259B
the other).
The bottom line for me is that I believe that the PT-11 introduces some sort
of SWR problem into the Pegasus on 18 MHz and above. I'm not planning on
reinstalling the PT-11.
comments?
73,
Mark, N8ME
(The following data will probabl look better using a fixed pitch font)
The columns are: frequency (MHz), SWR Reading on MFJ Analyzer, Pegasus SWR
w/PT-11, Pegasus SWR w/o PT-11
Tuner No Tuner
FREQ MFJ SWR Rig SWR Rig SWR
MHz
1.900 1.0 1.0 1.2
1.2 1.3 1.0
1.5 1.7 1.5
2.0 2.1 2.0
3.0 2.8 2.6
3.750 1.0 1.0 1.0
1.2 1.2 1.3
1.5 1.6 1.7
2.0 2.1 2.2
3.0 2.8 2.9
7.150 1.0 1.2 1.2
1.2 1.2 1.3
1.5 1.6 1.7
2.0 1.9 2.2
3.0 2.7 3.1
10.125 1.0 1.3 1.0 Analyzer Measured SWR was 1.1 for no tuner
1.2 1.6 1.0
1.5 1.9 1.6
2.0 2.4 2.1
3.0 3.0 2.8
14.175 1.0 1.0 1.0
1.2 1.0 1.0
1.5 1.2 1.4
2.0 1.7 1.9
3.0 2.4 2.6
18.118 1.0 1.6 1.0
1.2 1.0 1.0
1.5 1.0 1.5
2.0 1.3 1.9
3.0 1.9 2.6
21.225 1.0 1.8 1.0
1.2 1.9 1.0
1.5 2.0 1.4
2.0 2.4 1.9
3.0 2.7 2.5
24.940 1.0 2.0 1.2
1.2 2.2 1.2
1.5 2.5 1.6
2.0 2.9 2.0
3.0 3.5 2.9
28.850 1.1 2.0 1.3
1.2 2.0 1.3
1.5 2.4 1.6
2.0 2.8 2.2
3.0 3.5 3.0
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