On Mon, 24 May 2010 16:23:26 -0700 (PDT), Keith Dysart
wrote:

It is not at all obvious what exactly the result of performing the
procedure is. Does it result in the same load being applied to the
tube that was computed by the designer?

Hi Keith,

By and large, Yes.

There are some hints that
the procedure will result in the load applied to the tube being
real, but beyond that, what exactly are the circuit conditions
that result?

I am a little lost on that. The load applied is the load applied
(sorry for the Zen). If you mean that the load is transformed by
tuning to a real R for the Plate to see, then, yes, that is operative.

However, that is not the end of it. That R is seen as the loss of a
now-poorer Q for the Plate tank. This is the distinction between
loaded and unloaded Q. The Plate tank Q expressed in terms of loaded
Q, to be effective, is quite low in comparison to its unloaded value.
This value of loaded Q is roughly between 10 and 20 where the
components in isolation (unloaded) could easily achieve 10 to 30 times
that.

The term "loaded" includes BOTH the plate and the applied load
(whatever is presented to the antenna connection). The only time the
unloaded Q of the Plate tank is at peak value is when it is sitting in
isolation from the chassis, circuitry, and even mounts - which means
it is not very useful in that configuration, except as a trophy. Many
silver plate their tanks as trophies (because this rarely results in
better operation).

Now, let's return to my statement about what Q is "effective" AND that
it measures out at roughly 10 to 20. This is straight out of Terman
if you need a citation. As for explanation (also found in Terman),
you have to consider that the Plate tank is the gate-keeper (as well
as transformer of Z) of power. If you have too high a Q, the power is
not getting THROUGH the tank as it must, and necessarily it remains in
the tank (as energy, albeit).

Consider further that ALL resonant circuits can be cast from series
circuits to parallel circuits or parallel to series (a fact lost on
some inventors of antennas). To describe the Plate tank in series
terms as I do, then the plate resistance and load resistance combine
in series through a simple circular path through ground. There are
parallel tank designs where the resistances combine in parallel. The
net result is the same insofar as Q is concerned.

Consult Terman if that is confusing. No doubt others will either more
clearly cite him, or add to the confusion.

73's
Richard Clark, KB7QHC