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
MFJ-989
was (is?) a PI network tuner, the same as the SPC transmatch. Am I
incorrect?
It's been a few years since I sold it. Is a PI network and a T network
the
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
position
which provides the best match, then adjusting the inductor for best
match, then
going back to the capacitor and turning it counterclockwise. If SWR
increases,
then I go back to the hi/lo and keep trying a different positions until
rotating
the capacitor control counterclockwise lowers the SWR to an acceptable
point.
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
suppose
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.
Millen-style
turns counter, ceramic roller inductor, and another variable capacitor
instead
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
with
them. Just my opinion, mind you, but I think the construction is
"profit-motivated"
as opposed to "quality-motivated" like the rest of the Ten Tec line. Ten
Tec
wouldn't be able to sell them for $375 any more if they instituted my
suggested
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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