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Old July 16th 03, 10:22 PM
William E. Sabin
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Reg Edwards wrote:
"William E. Sabin" wrote

If a 50 ohm generator is connected to a 50 ohm
resistor (or resistance), the maximum possible
power is delivered to the load.

If the load is greater than or less than than 50
ohms resistor (or resistance) the power delivered
to the load is less than the maximum possible.


Unfortunately, the use of the term "Reflection Loss" to descibe performance
of amateur feedline + antenna systems at HF merely adds to the confusion.

"Maximum Available (or possible) Power" delivered to the load occurs only
when there's a "Conjugate Match" between generator and load.

But a Conjugate Match does not exist. It cannot even be assumed. For the
simple reason the internal impedance of the generator is never known. And
it wouldn't make any difference to how the system is set up and operated if
it was.

Even the generator (transmitter) designer doesn't know what the internal
impedance is. He couldn't care less. It can vary all over the shop depending
on what the load impedance is.

All of this is common knowledge, or should be.

However, this gets beyond the basic idea of
mismatch loss. It was not my intention to get into
an expanded discussion of the various
contingencies, which have been discussed ad
nauseum in this forum. One should start with the
simplest case.

If an equipment is designed to work into a 50 ohm
load, and the load is not 50 ohms, a "return loss"
can be measured with a 50 ohm directional coupler.
No knowledge of the generator impedance is needed
for this. The return loss is also a measure of the
mismatch loss, if the generator resistance (50
ohms) is known. An impedance "transforming"
network can improve the load impedance closer to
50+j0 ohms. The equipment will then perform as

In many kinds of circuits mismatch loss and
conjugate match are important.

Bill W0IYH