Ian Jackson wrote:
In message , Jeff writes



A load in isolation without any transmission line connected cannot have
a standing wave, but it is still common to quote the mismatch as a VSWR
which is plain wrong, but still very common.

But as I've said (nitpickingly), any length of connection (no matter how
short) where the load is not a perfect match for its characteristic
impedance, will have a very tiny portion of a standing wave on it.

I guess you could look at it that way, but the point is that such
effects are so small they are not measurable and irrelevant.

And as I've also said, the normal SWR meter DOESN'T measure (respond) to
SWR. It is a reflectometer, and it responds independently to the
forward-going signal and the reverse-going signal. It's really telling
you what the return loss ratio (RLR) is - but it's still perfectly
legitimate for it to be scaled in terms of SWR. It's a darned sight
easier way of finding out what the equivalent SWR would be than to try
and measure the Vmax and Vmin 'for real' along a long line.

Most scales do not measure weight, they measure the length of spring
extension, but they are calibrated to show pounds or kilograms.

Does that mean the measurement is not "real"?

The laws of physics allow one to both convert the forward and reverse
power measurements to VSWR and to convert spring deflection to weight.

As you say, it does not matter what a measurement device is actually
measuring, all that matters is that it is correctely calibrated to
display the information in the form you desire.


--
Jim Pennino