Reg Edwards wrote:

I disagree with this. When applied to transmission lines, the (voltage)
reflection coefficient is, as far as I can tell, universally defined as
the ratio of reflected to forward voltage to reverse voltage at a point.
So a reflection coefficient can be, and often is, calculated for every
point along a line, not just at discontinuities or points of actual
reflection.

This can be done with nothing more than the knowledge of the
values of forward and reflected voltages at the point of calculation.

=============================

Sorry! Just to continue and further confuse the haggling, the forward
voltages are unknown because one does not know, in the case of amateur
systems, what is the internal voltage and internal impedance of the
transmitter.

It is this unknown voltage and internal impedance which the so-called SWR
(Rho) meter merely ASSUMES.


Reg, that can't possibly be you. Someone has hijacked your e-mail.

Where is either of those assumptions required? Those are transmitter
properties, and they only affect the overall level of
power/voltage/current on the line. Reflection coefficient (rho) and SWR
are properties exclusively of the line and its load, not the
transmitter.

If you change anything at the transmitter, all forward and reflected
quantities change by the same scaling factor so their ratio stays the
same.

The SWR/rho meter measures reflection coefficient as a ratio of forward
and reflected signals. Either you yourself calculate the ratio of the
forward and reverse readings, or else you adjust the meter for
full-scale on the forward setting (which amounts to the same thing).

If you believe that rho has anything to do with the transmitter, you'd
expect to find some transmitter properties in the fundamental
definitions of what rho *is*. But they ain't there.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek