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Old March 5th 07, 12:57 AM posted to rec.radio.amateur.moderated
Mike Coslo Mike Coslo is offline
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First recorded activity by RadioBanter: Feb 2007
Posts: 168
Default Tube equipment question

wrote in
oups.com:


Most hollow-state ham rigs can handle 2:1 SWR no problem.
Sometimes there is less tolerance for loads that are highly
reactive, though.

What are the practical limitations of the Tube finals apparent
flexibility?


It's really a matter of how the rig was designed.

Many 1950s hollow-state ham rigs were built with pi-networks that
could match a wide variety of loads efficiently. The EF Johnson Viking
2 is a classic example of that type. Many
homebrew designs also had such pi-networks.

The problem is that the components for such a wide-range network tend
to be large, heavy and expensive. So in the late 1950s and early
1960s, rigmakers designed more for compactness than for wide matching
range. Still, the typical
ham rig of those days could usually handle SWR of 2:1 or
less with no problems.





Is it safe to compare the load, plate, and drive controls to some of
the functions of a tuner? (possible real dumb question)


The short answer is "no". Tuning up a hollowstate
ham rig is a similar but not identical to adjusting the
typical tuner.

Some may tell you that all it takes to tune up a tube
transmitter is to "peak the grid and dip the plate", but
that's simply not correct. Tuneup procedures vary
according to rig design and you have to be specific.


Of course once you get the hang of it, the procedure
rapidly becomes second nature.


I enjoy twiddling knobs, kind of the same way I like a manual
transmission. 8^)


What specific hollowstate rigs are you considering?



Last year at Dayton I purchased a 40 and 80 meter Heathkit single
Bander as a learning tool - they are pretty simple. I restored the
80 meter unit, and will start on the 40 meter one sometime. I am now
looking at a Kenwood TS-830S. It's a hybrid, with tube finals. I
really like it so far, although I don't see it replacing my IC-761.
I am hooked on computer control of the newer rig - sometimes! Other
times I just like that retro aspect.

- 73 de Mike KB3EIA -