View Single Post
 Dr. Slick Posts: n/a "David Robbins" wrote in message ...
"Dr. Slick" wrote in message
om...

[s]**2 = [(ZL - Zo*) / (ZL + Zo)]**2 the "power reflection
coefficent".

Note the squares.

yes, please do note the squares.... and remember, just because

[s]**2 = [(ZL - Zo*) / (ZL + Zo)]**2
does NOT mean that
s = (ZL - Zo*) / (ZL + Zo)

this is the one big trap that all you guys that like to use power in your
calculations fall into. just because you know the power doesn't mean that
you know squat about the voltage and current on the line. you can not work
backwards. that is why it is always better to work with voltage or current
waves and then in the end after you have solved all those waves you can
always calculate power if you really need to know it.

yes, but he does say that s = (ZL - Zo*) / (ZL + Zo) , first.

But he foolishly calls it a "power wave R. C."

Then he squares the magnitudes [s]**2 = [(ZL - Zo*) / (ZL +
Zo)]**2

And calls this the "power R. C."

The bottom label is fine, we've all see this before, as the ratio
of the RMS incident and reflected voltages, when squared, should give
you the ratio of the average incident and reflected powers, or the
power R. C.

But to call the voltage reflection coefficient a "power wave R.
C."
is really foolish, IMO.

Slick