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Old August 14th 08, 03:02 AM posted to rec.radio.amateur.antenna
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Posts: 666
Default Phase array question

Cecil Moore wrote:
Jim Kelley wrote:


Do you still believe that interference actually moves power
from one place to another?


Since I stated in my article that power doesn't flow, you are just
once more bearing false witness.


Let me try this then: Do you still think that interference is what
moves ENERGY from one place to another?

"The term "power flow" has been avoided in favor of "energy flow".


Yet, a couple of times a year just like clockwork, you accuse
me of saying that power moves (which I have never said). One
wonders what drives your never-ending vendetta obsession.


Note that the reason the author included the disclaimer about "power
flow" was because the term "power flow" had not been avoided by said
author in this newsgroup, in an argument which must have gone on for 6
weeks. In fact, it was a point that was never actually conceded.
Rather, thusly, he "avoided" conceding it. (Reminder: Now you come back
by mentioning how Poynting vectors show how much and in which direction
the power is flowing.)

It is simple physics to realize that (V1+V2)^2 is not usually
equal to (V1^2 + V2^2). When they are not equal, interference
has occurred.


Well, 8th grade algebra is supposed to help us realize that (V1+V2)^2 is
not equal to (V1^2 + V2^2). But the fact that (V1+V2)^2 is equal to
V1^2 + V2^2 + 2V1*V2 doesn't depend in the least on whether
"interference has occurred", Cecil. That was the whole point of my
comment about it.

In a transmission line, the power equation indicates exactly
by how much the resultant power deviates from the sum of the
component powers. The magnitude of that deviation from the
sum of the component powers is called the "interference term"
according to Hecht.


You'd think it would be enough for someone to throw out the whole idea
of "the sum of the powers" once and for all. But no. The inclination
instead is apparently to keep refining one's epicycle formulary. Hecht
makes no such connection between 'power' and 'interference', Cecil. And
why would he? There isn't one.....except in certain amateur radio
articles and newsgroup postings.

Ptotal = P1 + P2 + 2*SQRT(P1*P2)cos(A)

'A' is the angle between the V1 and V2 voltage phasors.


....and NOT between the two 'powers'. Still, it's a very useful
expression for finding a quick, albeit simplified solution. That is
after all its intended purpose.

73, ac6xg
 
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