Since I get the digest and have been very busy, I may be a day late and
a dollar short with these comments. Good to see some explanations of
the TT Design of the 238 family of tuners.
I have a 238 which works very well. I also came upon what I think was
meant to be a clone, except it wasn't. I thought that Paul from TT Service
had made it, because I thought I saw him with it on his table at a ham
fest, but I'm probably wrong.
Anyhoo, using the diagram for the 238 to rewire it correctly drove me and
a more technical friend crazy, trying to duplicate it using the two
sided one-
wafer switch it had. I finally got it figured out, and it works almost
as well
as the 238. I still don't have one position wired correctly - I think
one is
supposed to switch in a different cap, but not sure. I did wind the little
extra inductor that's used in one position. Not fancy metering in this one,
just the Tuning cap, variable inductor, switch and the extra fixed caps.
It has a military rotary turn counter which works quite well.
Balun - on yeah, that was the topic.....I used a military surplus one in
a 10" X 10"
(approximate) aluminum box, with feed through stand-offs and a coax
connector.
I think it's rated at 6 KW or so. 3 big toroids in there.
I've never tried to verify it, but think it's 9 to 1, or at least 6 to
1. I bought a
similar one from DX Engineering for a friend with a 126' dipole (like mine),
and they recommended a 1 to 1 for a remote balun. His works just fine, too,
on all bands with the 1500 watt TT amp and a 238c tuner, but my coax line
to the balun is short, where his is about 30'
or so. I assume the "ugly" balun is also a 1 to 1?
John, K4AVX
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