View Single Post
  #223   Report Post  
Old March 25th 08, 02:28 PM posted to rec.radio.amateur.antenna
Cecil Moore[_2_] Cecil Moore[_2_] is offline
external usenet poster
 
First recorded activity by RadioBanter: Mar 2007
Posts: 3,521
Default The Rest of the Story

Keith Dysart wrote:
Cecil Moore wrote:
Point is, energy can be stored and released at a
later time. You earlier said that reactances do not
store energy for release at a later time yet that
is exactly what reactances do.


Yes indeed. And what I have said, is that when this is
happening it is always possible to identify the element
which is storing the energy and provide the function
that describes the energy flow in and out of the
element. It is this identification and function that
I keep asking for to back up the handwaving claim that
you have been making.


Good grief, Keith, do you not know how to track the
energy flow into and out of a reactance during an RF
cycle? Isn't that covered in EE201, "Alternating
Current Circuits", by Kerchner and Corcoran, 3rd
edition (c)1951? Quoting page 19:

"The implication is that the inductive element
receives energy from the source during one-quarter
of a cycle of the applied voltage and returns exactly
the same amount of energy to the driving source during
the next one-quarter of a cycle."

The equations are provided if you really need them.
Hint: A shorted 1/8WL stub is inductive.

Bzzt. Power is the rate of change of energy.


Sorry, you are wrong about that.
From the IEEE Dictionary: "power - the rate of
generating, transferring, or using energy".

Power is a rate, not a rate of change. The
energy flow can be constant, i.e. rate of change
equal zero.

Please re-read all the equations with "(t)". There
is no "cos(theta)" factor when "(t)" is present.


I assume that exponential (phasor) notation for the
instantaneous values of the interfering voltages could
be used in which case there would indeed be a cos(theta)
present.

But this applies to RMS voltages and average powers.
You have extended this to instantaneous, for which a
"cos(theta)" factor is inappropriate.


Nope, it's not. See above. Your same argument could
extend to the real part of phasors in which case you
could argue that the irradiance equation is bogus.
Good luck on that one. If the math didn't work, it
would have been discarded long ago and Hecht wouldn't
have an entire chapter devoted to "Interference".

Read it as Pr.correction(t) to emphasize that it is not
average power of which I am writing. Then it is not
interference.


That statement makes it obvious that you don't understand
interference. When instantaneous values are being used,
if [V1(t)^2 + V2(t)^2] NOT= [V1(t) + V2(t)]^2, then
interference is present. Did you miss Physics 201?

Because the powers imputed to the
constituent voltages of superposition do not represent
actual energy flows.


That statement is a violation of the wave reflection
model. Do you really believe that when you look
yourself in the mirror that those reflections are
devoid of energy? If so, please feel free to prove
your assertion.

But you have to be cautious that you are applying
conservation to powers that represent actual energy
flows.


Reflected waves contain energy whether from your mirror
or from a mismatched load at the end of a transmission
line. You are arguing that the wave reflection model
is wrong. Please prove it.

Or perhaps, these powers of which you speak do not
represent actual energy flows and therefore your
requirement that they need accounting is incorrect
and all of your attempts to explain them, unnecessary.


Yes, perhaps the wave reflection model is wrong but
that makes your argument not with me, but with Ramo,
Whinnery, Johnson, Chipman, Slater, Hecht, and Walter
Maxwell. Good luck on winning that one.

The difficulty of accounting for these powers is entirely
consistent with them not representing the actual flow
of energy.


No, it is perfectly consistent with a large degree
of ignorance which few people desire to alleviate.

Ignoring the role of interference and lumping all the
energy components into a mashed potato salad is one
method of sweeping everything under the rug so you
can ignore the problem instead of solving it.

Or possibly, the premise that these powers represent
actual energy flows is flawed.


Feel free to prove the wave reflection model wrong.

This turns out, however, just to be an ideosyncracy of the math,
much like the way Pf-Pr is the actual energy flow in the transmission
line because of the way that Vf and Vr are derived from Vactual


Feel free to prove the math wrong.

It would be good, if just for a day, you let go of the
idea that Preflected represents an actual energy flow.


I will do that the day that you prove those reflections
from your mirror, that allow you to see yourself each
morning, contain zero energy. Your concepts seem more
like a religion than anything associated with reality.
Your mantra seems to be: "If I don't understand it,
it doesn't exist."
--
73, Cecil http://www.w5dxp.com