Sorry, it still isn't clear.

Richard Fry wrote:
"Roy Lewallen" wrote

But we seem to now have a "true SWR" as opposed to
some other kind of SWR. And "true SWR connected to
the tx output" doesn't have any meaning at all to me.


My "true SWR" term is used is an attempt to differentiate between the SWR of
the antenna system, and the inaccuracies associated with trying to measure
it with devices that cannot isolate the incident power in the system from
internal reflections of that power. For the conditions and reasoning
outlined in my earlier posts in this thread, and even though the system SWR
is a constant -- the normal SWR meter used in/with an operating transmitter
working into a mismatched load won't have the ability to give strictly
accurate measurement of that SWR. That is all I'm saying.

What, then, is "system SWR"? How do you define it?


I also have no idea of what "sample points within the
transmitter" might be.


In broadcast gear, these are the directional couplers whose pickup probes
are inserted transversely into the coaxial line between the harmonic filter
output and the tx output connector. I haven't been a licensed ham for over
40 years (when I went into the broadcast field), but I expect some ham txs
might have the same setup. Otherwise it could be a Model 43 or the like
inserted between the output connector of the ham tx and the transmission
line to the antenna.

In your last posting, you said,

Just one sec, please. I didn't say that the true SWR connected to the
tx output connector was affected. I said that the RF power measured
at the sample point(s) in the transmitter can be affected by the
source and load impedances of the tx, for the reasons stated.

So replacing "sample point(s) in the transmitter" with "Model 43 or the
like inserted between the output connector of the ham tx and the
transmission line to the antenna", you've said that the RF power
measured by the (model 43) SWR meter can be affected by the source
impedance of the transmitter.

Obviously, if we have a voltage or current source of fixed value and
change the source impedance, the power delivered by the source changes,
and any means of measuring the power at the source, load, or in between
should show that change. That follows from elementary circuit theory,
and doesn't require any consideration or knowledge of transmission
lines, waves, or SWR. On the model 43, both the "forward" and "reverse"
powers will change, but by the same fraction. Perhaps that's what you
mean. But if you mean that the SWR reading or the ratio of "forward" to
"reverse" power changes as a result of changing the source impedance,
that's easily shown to be false by the simple experiment I proposed.

I hope this is understandable now.

Almost, but not quite.