The haggling, for years, about congugate matching, SWR, forward & reflected
power, silly virtuallty, etc, has gone on long enough.

Only G3SEK, amongst the small minority of the radio population who
contribute to these walls, has a grasp of what it's all about. There are
obviously others who are too busy to waste their time on newsgroups.

But who am I to judge?

INTERNAL IMPEDANCE OF RF POWER AMPLIFIERS

Programs TRIODE1 and TETRODE1 assist with the classical design of tube
(valve) power amplifiers. They are very closely related to each other. A key
design feature, the cathode current operating angle, is an input parameter.

Apart from the drive and input-circuits, they also apply to their lower
power transistor equivalents.

For the benefit of those who may insist on knowing, these two programs are
based on the clssical theoretical analysis by americans Everitt, 1932 (who
was probably not original at that relatively late stage of the thermionic
tube). He was followed by Terman in a more practical but more uncertain
manner in the 1940's. No doubt there have been others. None of them, aware
of their weaknesses, would have wished to be worshipped as little tin Gods.

The basics havn't changed since Ohm, Ampere, Voltaire and Heaviside.

Anyone responding to an enquirer, who feels in need of extra support in his
reply, who refers back to the ancients merely displays his inability to
provide a logical explanation and a lack of underlying understanding.
There's nothing wrong, of course, in a lack of understanding except in
propagating it. (Most enquirers do not have the ancient books or easy access
to the books anyway)

Neither of this pair of programs require a congugate match between internal
impedance and the load. There's nothing magical about 50 ohms. It could be
any value as any appropriately designed SWR meter will assume. I have a
75-ohm model. All is based on assumptions. The only absolute value is SWR
itself which does not depend on Zo or Z load but merely on their ratio.

The only way to determine dynamic internal impedance of a PA is to calculate
it AFTER THE AMPLIFIER HAS BEEN COMPLETELY DESIGNED. It is then too late to
have any effect on design.

Just to satisfy curiosity the dynamic internal resistance of an amplifier is
a calculated output quantity of program TETRODE1. It is of course of no
practical value. In the program it is referred to as the Source Resistance
when looking back into the 50-ohm output socket.
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Regards from Reg, G4FGQ
For Free Radio Design Software
go to http://www.g4fgq.com
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