Roger wrote:
Roger wrote:
Keith Dysart wrote:
clip ....

In the setup above used for "standing waves"
it can be seen that there is zero power in
the line every 90 degrees back from the open
end. At a zero power point, no energy is
being transferred. Therefore, the forward
and reverse waves can not be transferring
energy across these points. Conclusion:
forward and reverse waves do not always
transport energy.

....Keith

Hi Keith,

You are basing this conclusion on the observation that Power = V*I,
and because we can not detect V or I at some points in the standing
wave, then V*I is zero at these points. Correct math, but wrong
conclusion.

What you are forgetting is that power is also found from Power = V^2/Zo
and Power = I^2*Zo. More accurately, on the standing wave line,
Power = (V^2 + I^2)/Zo. This is why a SWR power meter detects both
current and voltage from the standing wave.

This will also be true on the quarter wave stub, which is really 1/2
wave length long electrically, when you consider the time required for
the wave to go from initiation to end and back to beginning point.
Power is stored on the stub during the 1/2 cycle energized, and then
that stored power acts to present either a high or low impedance to
the next 1/2 cycle, depending upon whether the stub is shorted or open.

I think you did a very good job in building your theory. It was only
at the end (where I think we need to consider additional ways of
measuring power) that we disagree.

73, Roger, W7WKB

Haste makes waste, and errors as well. The standing wave power
equation is incorrect. It should read "Power = V^2 / Zo + I^2 * Zo"

Sorry for any inconvenience, and for the several postings it will
probably stimulate.

73, Roger, W7WKB

Contributing to this news group always carries the risk of making errors
and this was a DUZZY! "Power = V^2 / Zo + I^2 * Zo" IS VERY WRONG AND
SHOULD NOT BE USED AS DESCRIBED. Thanks to several folks for pointing
this out.

I was writing to describe a concept, a concept that was obviously wrong
upon closer examination.

73, Roger, W7KB