[TenTec] Pegasus Internal SWR

Tue, 8 Jan 2002 01:35:00 -0000

Mark,

I am a little skeptical about the test you did.  Don't forget that even with
the pegasus
internal tuner in bypass, it still creates a little SWR discontinuity.  This
discontinuity
would be more of a problem the higher in frequency you go.  Even when
you have two identical SWR meters in series, you will rarely read the same
SWR.
The first SWR meter will cause a discontinuity for the second one.  I always
felt
trying to get SWR to less than 1.5 was silly because even the SWR meter
itself
messes up the line it is on.  There's no way to measure SWR without changing
it!

Carl Moreschi N4PY
Franklinton, NC
----- Original Message -----
From: "Mark Erbaugh" <mark@microenh.com>
To: <tentec@contesting.com>
Sent: Tuesday, January 08, 2002 1:02 AM
Subject: [TenTec] Pegasus Internal SWR

> I have been having trouble getting good SWR readings on my Pegasus when
> using the PT-11 intenal tuner. Especially on the higher HF bands, when the
> tuner would finish tuning, the Pegasus SWR meter would still show SWR's
> close to 2:1.
>
> I have spoken with TT and LDG (makers of the PT-11 for TT). The consensus
is
> that the SWR bridge in the Pegasus is not that good and that the tuner is
> actually working properly.
>
> I ran a test to see if I could figure anything out.  I hooked up my
Pegasus
> to a manual antenna tuner and put a dummy load on the output. I made sure
> that the internal PT-11 tuner was bypassed. For frequencies at the center
of
> each of the bands 160 - 10, using my MFJ 259 antenna analyzer, I adjusted
> the SWR of the dummy load and antenna tuner to 1.0, 1.2, 1.5, 2.0 and 3.0.
I
> then recorded the forward and reflected power according to the Pegasus
when
> applying full power into the antenna tuner / dummy load, and calculated
the
> SWR using the formula:
>
> rho = sqrt( reflected / forward ).
> SWR = (1 + rho) / (1 - rho)
>
> I've listed the results below. Hopfeully, they are viewable if you select
a
> fixed pitch font. If not, let me know, and I can email you the Excel
> spreadsheet. The columns, in order are Frequency, SWR according the the
MFJ
> analyzer, R according to the MFJ, X according to the MFJ, Forward power on
> the Pegasus, Reflected power on the Pegasus and calculated SWR from the
> Pegasus values.
>
> For 160 and 80, the Pegasus tracks well.
> For 40, it got 1.2 for the 1.0 test, but tracked the other SWRs okay
> For 30, it seemed to register high for all but the 3.0 SWR
> On 20, it tracked well for low SWRs but read low for the higher SWRs
> On 17, it actually read a high SWR (1.6) for the 1.0 test and then read
1.0
> for the 1.2 and 1.5 tests and then was low for the 2.0 and 3.0 tests
> On 15, 12 and 10 the Pegasus was consistently high, reading 1.8 to 2.0 for
> the 1.0 SWR test and going up from there.
>
> If anyone else would like to run a similar test on their Pegasus, I'd be
> interested in seeing the results.
>
> One of my (paramoid) concerns is based on the fact that I installed the
> PT-11 upgrade myself. I wonder if these problems could be caused by
> something I did wrong in the upgrade, pehaps a cold solder joint (my
> nemesis).
>
> 73,
> Mark, N8ME
>
>
> FREQ SWR-M R X F R SWR-P
> MHz  OHM OHM
> 1.900 1 55 0 104 0 1.0
>  1.2 45 10 103 2 1.3
>  1.5 39 17 104 7 1.7
>  2 33 24 104 13 2.1
>  3 26 33 104 23 2.8
>
> 3.750 1 50 0 104 0 1.0
>  1.2 39 0 104 1 1.2
>  1.5 32 0 104 6 1.6
>  2 25 4 104 13 2.1
>  3 17 11 104 24 2.8
>
> 7.150 1 53 0 104 1 1.2
>  1.2 51 12 103 1 1.2
>  1.5 44 20 103 5 1.6
>  2 35 25 103 10 1.9
>  3 21 25 103 22 2.7
>
> 10.125 1 55 0 103 2 1.3
>  1.2 62 0 103 5 1.6
>  1.5 77 0 103 10 1.9
>  2 97 10 103 17 2.4
>  3 104 56 103 26 3.0
>
> 14.175 1 48 0 103 0 1.0
>  1.2 41 5 103 0 1.0
>  1.5 34 11 103 2 1.2
>  2 29 17 103 7 1.7
>  3 22 25 103 17 2.4
>
> 18.118 1 51 0 103 5 1.6
>  1.2 39 2 103 0 1.0
>  1.5 32 0 103 0 1.0
>  2 24 1 103 2 1.3
>  3 17 7 95 9 1.9
>
> 21.225 1 54 0 108 8 1.8
>  1.2 51 10 103 10 1.9
>  1.5 43 19 103 12 2.0
>  2 32 33 103 17 2.4
>  3 21 22 103 22 2.7
>
> 24.940 1 53 0 102 11 2.0
>  1.2 59 10 102 14 2.2
>  1.5 53 21 102 19 2.5
>  2 43 33 101 24 2.9
>  3 29 37 98 30 3.5
>
> 28.850 1.1 59 0 102 12 2.0
>  1.2 60 0 102 12 2.0
>  1.5 78 0 102 17 2.4
>  2 101 5 103 23 2.8
>  3 172 52 103 32 3.5
>
>
>
>
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