On Sun, 5 Sep 2004 12:47:45 -0500, (Richard Harrison)
wrote:

Richard Fry wrote:
"At least there appears to be an acknowledgement that some RF amplifiers
do not have a source impedance that is the conjugate of their load
impedance."

Those may be anomalous. I recommend King, Mimno, and Wing to anyone
desiring the complete story on the conjugate matches.

To the extent that the amplifier is designed for a performance on demand
that stresses it to its maximum safe dissipation, an amplifier of the
Class C variety is designed for a perfectly matched load. It`s the
economical thing to do.

You supply the tube with about all the volts it can safely take. Then
you supply it with just enough load impedance to limit its current to
all it can take under the heaviest loading it well encounter. That would
be when it is conjugately matched to a 50-ohm load, the usual cable
impedance specification.

The tank circuit is mostly a harmonic filter providing a very high
impedance to the fundamental frequency and shorting out the harmonics.

Best regards, Richard Harrison, KB5WZI

Gotta' disagree here, Richard, conjugate matching a Class C tube amp doesn't
require the heaviest loading it will encounter. A conjugate match can be
obtained with any loading you choose. For example, you can set the drive that
will permit loading to any particular level of maximum output power into any
load within the tank circuit's available matching range. So let's assume you set
the drive to provide a max output of 100 w into a 50-ohm load by adjusting the
tank controls for maximum output. The source resistance is now 50-ohms, there is
a conjugate match, and the amplifier has not been loaded to the heaviest
loading it will encounter. In addition, if the load was 70 ohms and the tank
adjusted for maximum output, the source resistance would now be 70 ohms, and
there'd also be a conjugate match.

If you question my statements above see the data from my measurements using
professional grade instruments in either QEX, May/Jun 2001, Chapter 19 in
Reflections II, or from my web page at http://home.iag.net/~w2du.

Walt