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Old March 5th 07, 02:10 AM 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, 6:57�pm, Mike Coslo wrote:

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)

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^)

It's a question of skill vs. automation.

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 think you mean the Heath HW-12 and HW-22, or the later
A models of the same rigs.

They are from the early-to-mid 1960s, and have very limited
matching range. They are really only meant to match a 50
ohm load. Note that there isn't even a LOADING control on

The Single Banders were Heath's answer to the "SSB is too
expensive" idea. Every possible simplification and economy
measure was used in them, yet the result is a usable 100 W
class SSB transceiver for one HF ham band. Note that the
75 meter one stops at 3.8 MHz. Heath figured that by
simplifying the output pi network to the most extreme degree,
they could save a few dollars. Coming up with a 50 ohm
antenna was the ham's problem.

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.

That's a pretty good rig for its era. The matching range is limited
but it will handle 2:1 SWR without problems IMLE.

I am hooked on computer control of the newer rig - sometimes! Other
* * times I just like that retro aspect.

One of the great things about amateur radio today is that we can
use a wide variety of technologies for the same or similar purposes.

I find it ironic that the evolution of the "state of the art" has come
full circle in about a half-century, at least in HF/MF:

- Ham rigs of the 1950s usually had wide range pi-nets which required
adjustment, but would match almost anything without an external
- Ham rigs of the 1960s and 1970s usually had restricted-range
pi-nets which were easier to adjust, but sometimes required an
external matching device.
- Ham rigs of the 1980s and later usually have solid-state finals and
no adjustment - and usually require an external matching device.

73 de Jim, N2EY