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[TenTec] RE: Request for comments about 238 tuner

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Subject: [TenTec] RE: Request for comments about 238 tuner
From: kr4wm@sccoast.net (Webster D. Williams)
Date: Sat, 20 Sep 1997 14:55:32 -0400
AE0Q V31RY wrote:

>   Ah HAH, Webster, there is a reason for that!!!   L-match circuits are much
> better than the usual T-match (most MFJ tuners) because they will only find
> a match in one place, and that is the most efficient point.  The T-match is
> capable of showing a 1:1 match in an almost infinite combination of
> settings, and many times a lot of power is dissipated in the tuner circuits.
> So it appears easier to tune with!  I used to have an MFJ-989C and it was
> typically less efficient than the 238, once a match is found with the 238..
> I've burned up an MFJ-949 150w T-match with only 100 watts (melted the coil)
> because the 1:1 match it showed was at a very inefficient point.  Can't
> happen with an L-match circuit.

I replied to someone earlier, and was under the impression that the
was (is?) a PI network tuner, the same as the SPC transmatch. Am I
It's been a few years since I sold it. Is a PI network and a T network
same? Perhaps I'm confused?

>   Most of the MFJ tuners (the 941, 949, and big 989) are T-match.  The SPC
> circuit requires a much more expensive split-capacitor.
>   Are you following the Ten Tec instructions for initially selecting the Low
> or Hi side of the fixed caps?  I had problems too until I went back and
> re-read the manual.  Just a thought..

I'm setting the capacitor to 2, inductor to 30, the selecting the lo/hi
which provides the best match, then adjusting the inductor for best
match, then 
going back to the capacitor and turning it counterclockwise. If SWR
then I go back to the hi/lo and keep trying a different positions until
the capacitor control counterclockwise lowers the SWR to an acceptable
This is per my owners manual.

My manual specifically makes note that if the capacitor is set at less
than 2, 
then something is wrong, and you need to try a different hi/lo tap.
Seems like 
they'd calibrate the knob where the 2 position has a zero at that point.
I dunno.

I was never able to reproduce low SWR points with my MFJ tuner at more
than one 
knob position. I understand that older (tube-type) radios were prone to
having more 
than one peak output setting, which would cause spurious harmonics. I
tuners could be prone to the same problems, as would any tuned circuit.

My primary argument with the Ten Tec tuner is NOT that it is difficult
to tune, 
rather, for almost $400, it should have better components. (i.e.
turns counter, ceramic roller inductor, and another variable capacitor
of fixed-value switched capacitors.) I have no beef with the "T"
circuit. I 
dislike linear tuning scales and the slop that inherently comes along
them. Just my opinion, mind you, but I think the construction is
as opposed to "quality-motivated" like the rest of the Ten Tec line. Ten
wouldn't be able to sell them for $375 any more if they instituted my
mechanical changes, but only because they want/need (my opinion) a
higher profit 
margin. I think it would cost them an extra $50-$75 to produce, and
they'd want 
to tack on a profit margin on that additional cost. Then who'd pay $500
for a tuner? 
I'd also add weighted knobs while I was at it. Then it would be a KR4WM
tuner, not 
a Ten Tec, and would cost $600, HI HI!

I'll live with it as-is, and wish for the sun while Ten Tec delivers
Mars at the cost 
of the Moon- a good-natured 73 to you and yours, Web

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