On Thu, 27 May 2004 17:24:40 -0500, Cecil Moore
wrote:



Hank, when reflected current flows backwards through a pi-net loading
coil, some of the reflected power is dissipated as I^2*R losses in
the coil. Other than that, a properly tuned pi-net causes a match
point that reflects all the reflected energy back toward the load.


This is a great thread, I have a question about your post. If the all
the reflected energy is reflected back toward the load, is it in phase
with the original or subsequent energy? or does it matter?

If a match point exists in a ham radio antenna system, no reflected
energy will reach the source. This is the great majority of amateur
radio systems and no-reflections-at-the-source is the goal of every
ham. The thing that you are worried about is the unusual case where
reflections are allowed to reach the source.

Ken wrote:
This is a great thread, I have a question about your post. If the all
the reflected energy is reflected back toward the load, is it in phase
with the original or subsequent energy? or does it matter?

I am from the old school, Ken. I believe that power is a scalar and
doesn't possess phase. IMO, any phase calculation that you see being
used on power originates from the voltage phase and/or current phase
associated with that power. It is done all the time in optics.

The answer to your question is, assuming PA stands for Phase Angle:
Since forward voltages and forward currents are in phase, V*I*cos(PA)
yields watts with no vars. Since reflected voltage and reflected current
are 180 degrees out of phase, V*I*cos(PA) yields watts with no vars.
So extremely loosely speaking, the "phase" of the power can be considered
to be the same as the phase of the voltage or current since they are
the same phase. However, such a consideration cannot be considered to
be good physics.
--
73, Cecil http://www.qsl.net/w5dxp




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Cecil Moore wrote:

I am from the old school, Ken. I believe that power is a scalar and
doesn't possess phase. IMO, any phase calculation that you see being
used on power originates from the voltage phase and/or current phase
associated with that power. It is done all the time in optics.

Interesting comment, however the "power" companies would have a great
difference of opinion with you.

And no, I'm not about to enter this very silly argument you wish to
continue, apparently until the protons all decay.

tom
K0TAR

Tom Ring wrote:
Cecil Moore wrote:

I am from the old school, Ken. I believe that power is a scalar and
doesn't possess phase. IMO, any phase calculation that you see being
used on power originates from the voltage phase and/or current phase
associated with that power. It is done all the time in optics.

Interesting comment, however the "power" companies would have a great
difference of opinion with you.

My degree is in Power Engineering and I learned the above at
Texas A&M. Of course, Volt-Amps have a phase, but power always
lies along the real axis. What would be the physical meaning of
25 watts at 45 degrees?
--
73, Cecil http://www.qsl.net/w5dxp



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