Gary-
Thanks. Makes sense.
After looking at your page, I see what you are calling an SPC is what
I am calling my T. It works great.
Heating the case, eh? Will try with cover off next FD.
-Bob
Gary Bold wrote:
> 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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