[TenTec] Jupiter/LDG AT-11MP Tuner

Wed, 8 Jan 2003 08:30:14 -0500

I have had a very good experience with both the LDG AT11MP and the RT11
tuners when used with my Pegasus and other radios. However, I did not have
the same results with the internal tuner for the Pegasus and I have removed
it and gone back to the outboard tuners. I found that there were many
situations where the internal tuner would not find an SWR less than 2, while
the outboard tuner would get 1:1. I even sent the Pegasus w/ internal tuner
to LDG for adjustment and they could find nothing wrong. I believe that the
internal tuners, while similar, are not the same as the ouboard ones.

One problem with using the Jupiter and Pegasus' SWR indication is that
reflected power is only measured to the nearest whole watt. This makes the
SWR calculation very 'granular', particularly at lower foward power
settings. Below is a table (best viewed with a fixed pitch font) that shows
that SWR based on forward (across the top) and reflected (down the left
side):

 100.0 50.0 25.0 20.0
0 1.0 1.0 1.0 1.0
1 1.2 1.3 1.5 1.6
2 1.3 1.5 1.8 1.9
3 1.4 1.6 2.1 2.3
4 1.5 1.8 2.3 2.6
5 1.6 1.9 2.6 3.0
6 1.6 2.1 2.9 3.4
7 1.7 2.2 3.2 3.9
8 1.8 2.3 3.6 4.4
9 1.9 2.5 4.0 5.1
10 1.9 2.6 4.4 5.8
11 2.0 2.8 4.9 6.7
12 2.1 2.9 5.5 7.9
13 2.1 3.1 6.2 9.3
14 2.2 3.2 6.9 11.2
15 2.3 3.4 7.9 13.9
16 2.3 3.6 9.0 17.9
17 2.4 3.8 10.4 24.6
18 2.5 4.0 12.2 38.0
19 2.5 4.2 14.6 78.0

You can see that with 20 watts out (right column), when the reflected power
goes from 0 to 1 watt, the SWR jumps from 1.0 to 1.6 - with 20 watts out,
there is no way to get any SWR readings between 1.0 and 1.6. With higher
power, you do get better resolution.

Since the LDG tuners have their own SWR bridges, I don't think that this
resolution issue affects the operation of the tuner, just what is displayed
by the radio.

Mark

----- Original Message -----
From: "Lee Groce" <n4aad@yadtel.net>
To: <tentec@contesting.com>
Sent: Wednesday, January 08, 2003 0:59 AM
Subject: Re: [TenTec] Jupiter/LDG AT-11MP Tuner

>
> ----- Original Message -----
> From: <WmLB@attbi.com>
> To: <tentec@contesting.com>
> Sent: Tuesday, January 07, 2003 23:35
> Subject: [TenTec] Jupiter/LDG AT-11MP Tuner
>
>  Hi Bill,
>  I bought a Jupiter with the internal antenna tuner in early April 2002.
> It has acted strange at times too. TT told me as long as swr did not
> exceed 2:1 I would be ok.
>
>  Last Saturday, a friend dropped by and I showed him my Jupiter.
> I had the power at about 40 per cent and noticed as he played with
> the key swr was nearing 2:1 on 40 Meter CW. After he left, I played
> around and could not get swr below 2:1 on any band.
> Two days ago I was on 40 Meters and the internal tuner tuned from
> 1.0:1 to 1.6:1 on all bands just fine.  Now I am confused! This is not
> the first time this has happened either.
> For those who may think it's in my antenna; when my internal auto
> antenna tuner would not tune below an swr of 2:1 and higher, my manual
> antenna tuner tuned to 1.2:1 as soon as I put it in line.
>
> I want to talk to the folks at TT and see if they will take out my
> internal
> antenna tuner and replace it with the external LDG AT-11MP Tuner
> thinking it may work better.
>
> Has anyone else experienced similar problems with the Jupiter/AT ?
> After reading what Bill has to say, I am at a loss of what to do.
>
> 73,
> Lee  N4AAD
>
>
> > I bought the subject tuner Saturday for use with my Jupiter.
> >
> > It has been acting a bit "squirrely" I guess. It tunes for a good SWR
> on
> > low power  but that SWR seems to increase as output is increased.  In
> most
> > cases I can touch up the SWR (under higher power) using one or both of
> the
> > Cap and Ind. Up/ Down switches. These increase or decrease those two
> > elements in incremental amounts (fine tuning  I guess you would call
> it.)
> >
> > I called LDG today and was left with two thoughts:
> >
> > 1.  I should not try to reduce the SWR at power levels any greater
> then 25
> > watts or so.
> >
> > 2.  He mentioned that there has been some reported "problems"
> > (un-specified) with the tuner working properly with Ten-Tec rigs. Part
> of
> > it apparently related to the fact that the TT rigs do not "fold -back"
> at
> > higher SWRs.
> >
> > I am sort of inclined to return this tuner, but thought I would ask
> here
> > and see if there is any "real world" knowledge on the compatibility
> (or
> > lack thereof)  between these two pieces of equipment.  I know Ten-Tec
> was
> > marketed a internal version of the AT-11 in kit form for use in the
> > Jupiter. I guess that made me assume that the external version would
> also
> > insure a large degree of compatibility.
> >
> > Any comments would be appreciated..  I subscribe to the digest so, if
> you
> > have timely comments that you think are significant in helping me
> decide
> > what to do.. please email me direct.
> >
> > Thanks..
> >
> > Bill, W6WLB
> >
> >
> > _______________________________________________
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> > TenTec@contesting.com
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> >
>
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