Richard Harrison wrote:

Proof is that a directional sensor finds the same power flow, forward
or reflected, at a standing wave zero point as it does at a standing
wave maximum, or at any point in between.

Richard's statement about what the directional sensor "finds" is
perfectly correct - but unfortunately it cannot be used as proof.

The reason is that so-called "directional wattmeters" don't physically
sense directional power flow. All they sense from the transmission line
are the current and the voltage, as two separate samples. Then they add
or subtract these samples to give the sensor its directional properties.
All the meter reads is a detected RF *voltage*, which changes to a
different value when the sensor is reversed.

If you want to know what those meter readings mean, you need
transmission-line theory in order to understand them. You can then
calibrate the meter to read forward and reverse power - but you cannot
do that without using transmission-line theory to do it, and that theory
is the subject of this entire discussion.

Therefore the readings of a "directional wattmeter" cannot be used as
evidence for either side, because that argument would be circular - you
cannot use any theory to prove itself!


However, this attempt to use inadmissible evidence doesn't necessarily
affect Richard's wider argument about power flow. If that argument is
correct, there definitely *will* be other physical evidence to prove it.


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