Bob,
both my MFJ tee tuners eat watts, because the coil sits too close
to the metal case, which gets warm. I've replaced the case top with
cardboard, which increases the Q and decreases the losses.
Some years back, I wrote a document describing the theory and
design of tee transmatches, which you can find here.
http://www.phy.auckland.ac.nz/Staff/geb/transm.pdf
For lowest loss, tees should use the largest possible C, as this
decreases the voltage across the coil. It's possible to estimate the
power loss from the coil Q if you estimate a few other values. I
estimate
that a good tee transmatch will absorb maybe 5 - 15% of the power
applied to it - more for the commercial "miniature, compact" designs.
Gary ZL1AN
At 03:43 PM 6/30/03 -0400, you wrote:
Well it was the MFJ that seemed to be eatin half my watts.
The T match (hombrew) worked great. Set C's to low value,
find resonance with L, peak with C's.
I suspect the MFJ just loses a lot in the tiny components...
My traveling 'tuner' is a BCB variable cap, a hand wound coil,
and some clip leads. Just lay the parts out on the table top, rock,
or whatever is reasonably flat and non conducting. TX output
is a pair of 24" clip leads to the matchng network and antenna
is wire tossed up and out in opposite directions. Simple and works.
-Bob
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