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Old March 4th 07, 09:53 PM posted to
[email protected] N2EY@AOL.COM is offline
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First recorded activity by RadioBanter: Jul 2006
Posts: 877
Default Tube equipment question

On Mar 4, 12:48?pm, Mike Coslo wrote:
Solid state transmitters are notoriously finicky about matching to the
antenna. Tube equipment is not, so I am told, and early experience seems
to bear that out.

IMHO, it's really a matter of the actual circumstances. As far
back as the late 1950s there were hollow-state ham rigs made
that were meant for 50 ohm loads only. In fact, there
were some HF tube ham rigs made that required no conventional tuneup
at all (CE 100V, 200V, 600L).

Certainly I can see one of my newer rigs start to fold back at 2:1.

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

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)

Not a dumb question at all IMHO.

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.

What specific hollowstate rigs are you considering?

73 de Jim, N2EY