Reg Edwards wrote:
Cec, you can make the meter read anything you like just by twiddling
the calibration pot. Of what bloody use is that? !**?!!

Just answer the obvious question. No If's or But's

I did answer the question, Reg. You just didn't like the
answer.

Let's say we have an SWR meter at point 'x' in the following
diagram:

XMTR---1WL 50 ohm coax---x---1WL 75 ohm coax---100 ohm load

If the meter is calibrated for 50 ohms, it will indicate the
SWR on the 50 ohm coax, 2:1, on the source side of the meter.

If the meter is calibrated for 75 ohms, it will indicate the
SWR on the 75 ohm coax, 1.33:1, on the load side of the meter.

An SWR meter samples the magnitude and phase of the voltage,
samples the magnitude and phase of the current, assumes
it exists in the Z0 environment for which it was calibrated,
and accurately reports those results.

If the SWR meter is installed in a Z0 environment other than
that for which it was calibrated, the instrument is being
misused and the operator is at fault, not the instrument.
Any instrument can be misused.
--
73, Cecil http://www.qsl.net/w5dxp