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Owen Duffy · June 11th 10, 09:31 PM posted to rec.radio.amateur.antenna

Richard Fry wrote in news:908e1320-965a-4e11-b02b-
:

On Jun 11, 6:16*am, Owen Duffy wrote:

... The transmitter output power is probably different ...

Thank you, Owen.

Do your comments apply to a transmitter designed/adjusted for, and
expecting a 50 + j 0 ohm load?

In answer to the question you directly asked, yes. But that says nothing
of whether such a transmitter, in the general case, is well represented
by a Thevenin equivalent circuit with Zeq=50+j0.

As you know, there is a proposition that a transmitter "designed/adjusted
for, and expecting a 50 + j 0 ohm load" can be well represented by a
Thevenin equivalent circuit and naturally has Zeq=50+j0. However, that
proposition is easily proven wrong by valid experiments in the real
world, and those of us who have done such experiments are disinclined to
accept the proposition.

IOW, if the net output power of such a transmitter (which equals that
dissipated in the load) probably is different with such a mismatch, do
you expect the reason for that to be related to "reflected power?"

Average power at the transmitter terminals is given by the average value
of the instantaneous product of v and i over time. There is no need for
"net" in the calculation. The average power delivered by the transmitter
will depend on the load impedance (ie the complex ratio of v/i) at its
load terminals, but that dependence is not well predicted in the general
case by a Thevenin equivalent circuit.

I gave a link to a simple experiment to test Zeq of a tx, and that uses
equipment found in most ham shacks. The article is at
http://vk1od.net/blog/?p=1028 .

Owen