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Old September 6th 03, 12:25 AM
Dr. Slick
 
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W5DXP wrote in message ...
Dr. Slick wrote:
The concept of phase is meaningless for power.


Actually, in a transmission line, it's not. Reference Dr. Best's
QEX article. He introduces a term familiar to the field of optics:

P1 + P2 + Sqrt(P1*P2)cos(delta)

where delta is the angle between V1 and V2.

Sqrt(P1*P2)cos(delta) is the interference term whose magnitude
depends on the phase between two voltages. If the phase between
V1 and V2 is less than 90 deg, the sign of that term is positive
and the interference is constructive. If the phase angle between
V1 and V2 is between 90 deg and 180 deg, the sign of that term
is negative and the interference is destructive.



Ok, well perhaps Dr. Best is talking about constructive and
destructive
interference, but i'm just talking about incident and reflected power.

Page 32 of "Electronic Applications of the Smith Chart":

"The power RC is defined simply as the ratio of the
reflected to the
incident power in a waveguide. Numerically it is equivalent to the
square
of the voltage reflection coefficient (atually, this should be
Magnitude-Slick).
However, unlike the voltage RC, the power RC has magnitude only, since
'phase' as applied to power is meaningless."


Slick