From: Mike Coslo on Sun 4 Mar 2007 22:56

" wrote:

Besides old ARRL Handbooks prior to the 1970s, I'd suggest
finding the site that has digitized copies of GE Ham News.
Those were (bi-monthly?) hand-outs by GE to push their
tubes (naturally) but they contained lots of different ham
projects (using tubes, of course).

Got it! Thanks a lot Len - I googled them up, and have enough reading
material to keep me busy for a while.

the site is: http://bama.sbc.edu/ge_ham_news.htm

Thanks for the reminder on BAMA contents. BAMA has more
than just old tube equipment manuals. :-) Good site!

On the general subject of tube PA matching to load, some
remarks:

The automatic antenna tuner might have its beginning at
Collins Radio of the 1950s decade. Reference is the T-195
transmitter, part of a set that used the special version
of the R-390 series called the R-392, designed and built
for the USMC, first fielded in 1955, intended to be Jeep
mounted. The basic whip antenna matching was a servoed
single variable L and a single variable C to a conventional
PA output tank...so-called Ell-network, switchable to
the four possible L-C connection possibilities. On an
Army demo in late 1955, I was most impressed when the
demonstrating officer simply removed half of a whip
section (!), hit the tune function, and the servo
system re-tuned to this new antenna impedance in
seconds. :-)

Warren Bruene must have had a hand in that Autotune
labeled antenna matcher because it has the first instance
I've seen for the "Bruene detector" in the transmission
line to get both amplitude and phase of the RF. Slight
variations of that exist today, generally with a toroid
for current output and a small capacitor for voltage
output, both combined into dual diode detectors. Today's
antenna auto-tuning subsystems use binary-progression
switched single inductors and single capacitors with the
servo system basically a microcontroller plus small
frequency counter (sometimes) that can determine which
L or C to switch and remember the frequency and setting.
SGC (Stoner Goral Company) in the Puget Sound area of
Washington state has at least three models for both
maritime and amateur radio HF use. The Big3 (Icom,
Yaesu, Kenwood) have them, either built-in or as out-
board boxes. Several independent USA companies have
them.

ALL (no exceptions) antenna tuners have limits on
their impedance matching capabilities, whether "Pi-L"
output tanks or big boatanchor style structures
that look very impressive. There are few overall
advantages in any configuration with the possible
exception of Simplicity of the single L, single C
variety now common to today's autotuning matchers.
ALL, even the popular Pi-network, have limits that
can be proven mathematically; if the math doesn't
fit, no amount of publicity or historical references
will make it fit better.

If you or anyone else would like an algebraic-only
math explanation of the four combinations of single
L and C matching combinations...with their limits of
load impedance variation, I'll be happy to forward
them by e-mail attachments. No binary files here
and the equations, figures are better shown in the
PDF format.

73,

wrote:



If you or anyone else would like an algebraic-only
math explanation of the four combinations of single
L and C matching combinations...with their limits of
load impedance variation, I'll be happy to forward
them by e-mail attachments. No binary files here
and the equations, figures are better shown in the
PDF format.


I would appreciate that very much, Len. This address would be fine.
Thanks - Mike -