"Walter Maxwell" wrote
What seems to be overlooked here is that the source resistance at the
output
terminals of the pi-nework in Class B and C amplifiers is non-dissipative,
which
is the reason they can be loaded for delivering all available power for a
given
grid drive, and still have efficiencies greater than 50 percent. One of
the
myths circulated for years, and still prevelant, is that the reason for
Class B
and C amps to have efficiencies greater than 50 percent is that the load
resistance must be greater than the source resistance. Tain't so.
____________

Walt - what is your thinking on the point that untuned, solid-state
amplifiers also can have PA DC-to-RF power conversion efficiencies of 70% or
more at the device level?

In fact the solid-state, analog FM broadcast transmitters supplied by Harris
Corporation and others need no tuning to produce their rated output power
into a 1.3:1 SWR or less, anywhere in the FM broadcast band 88-108 MHz.
Even the harmonic filter needs no changes, and maintains harmonics at -80
dBc or better. They are frequency agile, and can be reset from one carrier
frequency to another, anywhere in the FM band with a transition time of a
few seconds

The overall AC input to r-f output efficiency of these transmitters exceeds
60% (includes the exciter, control system, IPA, and cabinet fans).

RF

Richard Fry wrote:
"Walter Maxwell" wrote
What seems to be overlooked here is that the source resistance at the
output
terminals of the pi-nework in Class B and C amplifiers is
non-dissipative, which
is the reason they can be loaded for delivering all available power
for a given
grid drive, and still have efficiencies greater than 50 percent. One
of the
myths circulated for years, and still prevelant, is that the reason
for Class B
and C amps to have efficiencies greater than 50 percent is that the load
resistance must be greater than the source resistance. Tain't so.
____________

Walt - what is your thinking on the point that untuned, solid-state
amplifiers also can have PA DC-to-RF power conversion efficiencies of
70% or more at the device level?

In fact the solid-state, analog FM broadcast transmitters supplied by
Harris Corporation and others need no tuning to produce their rated
output power into a 1.3:1 SWR or less, anywhere in the FM broadcast band
88-108 MHz. Even the harmonic filter needs no changes, and maintains
harmonics at -80 dBc or better. They are frequency agile, and can be
reset from one carrier frequency to another, anywhere in the FM band
with a transition time of a few seconds

The overall AC input to r-f output efficiency of these transmitters
exceeds 60% (includes the exciter, control system, IPA, and cabinet fans).

RF

I know this question was directed to Walt, but I'd like to mention that
I've designed and built solid state class C amplifiers at the 5 - 10
watt level which have measured efficiencies of greater than 85%.

Roy Lewallen, W7EL

"Richard Fry" wrote in message ...
"Walter Maxwell" wrote
What seems to be overlooked here is that the source resistance at the
output
terminals of the pi-nework in Class B and C amplifiers is non-dissipative,
which
is the reason they can be loaded for delivering all available power for a
given
grid drive, and still have efficiencies greater than 50 percent. One of
the
myths circulated for years, and still prevelant, is that the reason for
Class B
and C amps to have efficiencies greater than 50 percent is that the load
resistance must be greater than the source resistance. Tain't so.
____________

Walt - what is your thinking on the point that untuned, solid-state
amplifiers also can have PA DC-to-RF power conversion efficiencies of 70% or
more at the device level?

In fact the solid-state, analog FM broadcast transmitters supplied by Harris
Corporation and others need no tuning to produce their rated output power
into a 1.3:1 SWR or less, anywhere in the FM broadcast band 88-108 MHz.
Even the harmonic filter needs no changes, and maintains harmonics at -80
dBc or better. They are frequency agile, and can be reset from one carrier
frequency to another, anywhere in the FM band with a transition time of a
few seconds

The overall AC input to r-f output efficiency of these transmitters exceeds
60% (includes the exciter, control system, IPA, and cabinet fans).

RF

Hello Richard,

Sorry, Richard, I have no knowledge of solid-state untuned amps, so my thinking
on them is zero, nada. As you'll note, all of my discussion on the subject
concerns only tube amps with a pi-network output, and I've specifically stated
these conditions.

If you've read Chapter 19 and its addition as Chapter 19A, do you agree with my
position that the output resistance at the output terminals of the pi-network is
non-dissipative?

Walt, W2DU