On Fri, 18 Jul 2003 16:01:43 -0400, "Tarmo Tammaru"
wrote:

Yeah, seems to be a deep dark secret. If you look at the specs of RF power
transistors, they will give the output impedance vs frequency - BUT you have
to look at the footnote. In virtually all cases what they mean is the
conjugate of the load impedance. It is the jX of the transistor (1/jY), in
parallel with
((VCC-Vsat)**2) /2P.

Hi Tam,

Motorola offers quite specific characteristics across frequency.
Reference MRF421, MRF433, MRF454 for examples of dirt ordinary power
transistors found in more than 20 years of transistorized Ham
transmitters. Take their own data, Z transform them through
transformers (not transducers) and you find 50Ohms without any more
sophisticated math than that required of the standard Technology
Certificate of training. Where does it go through after that? A low
pass filter designed for 50Ohms to an antenna jack specified to
deliver full power to a 50Ohm load.

What technical rebuttal do I hear in response to simple engineering
data? "It is impossible to determine the output Z of this source."
For some I can well imagine they do find it difficult....

73's
Richard Clark, KB7QHC