On Sat, 05 Jun 2004 15:23:37 -0500, Cecil Moore wrote:

Walter Maxwell wrote:
Yes, Cecil, I understand. However I don't particularly like the notion of saying
both fields go to zero, or both fields go to zero in the rearward direction.

But Walt, that's exactly what happens when total destructive interference
occurs as explained by J. C. Slater in _Microwave_Transmission_.

I believe voltage 180 out defines a short--period.

That same belief is what got Dr. Best into trouble. He never considered
what happens to the reflected current waves. In a sense, your and his
disagreements are because you both made the same conceptual mistake and
arrived at different conclusions because of that common mistake. If you
and he had not made that shared mistake, you both would have arrived at
the same conclusions.

Cecil, how do you figure I made a mistake in this issue? I have always
considered voltage 180 out as a short. And my writings show voltage at 180 as a
short, as stated on page 23-9. I agree that the opposite phases of both voltage
and current in that discussion resulted in the cancelation of reflected power
traveling in the 225-ohm section of line. And during the last day or two I
leaned toward thinking the out of phase current implied an open circuit. But you
can see from my words above that voltage rules--when the voltages are 180 out of
phase it defines a short circuit. My zip cord example is evidence to that.
Consequently, I don't agree that Steve and I made the same mistake. My writings
delivered the correct mathematical answers--Steve's does not. The mistake I made
on page 23-9 is in overlooking that it is the effective open circuit condition
seen looking in the rearward direction by the reflected waves at point A is what
gave both the voltage and current waves the reversal and phase change to zero
relative to the source waves.

Another scenario with the same initial conditions and results: Take two
identical generators delivering the same level of harmonically related output
voltages. Connect their terminals in phase.Voltages in phase--currents in phase.
Result? No current flow. Why? Zero voltage differential. Open circuit to
voltage--open circuit to current.

Now reconnect their terminals in the opposite manner. Voltages 180 out--currents
180 out. Do we have current flow? You bet--dead short! Because current results
from voltage, if voltages are 180 out of phase we have a short to both voltage
and curent. No open circuit to current.

This is the problem with trying to use circuit analysis to replace network analysis.
Put the two sources at the two ends of a transmission line and please reconsider
the outcome. Equip the two sources with circulators and dummy loads so the outcome
cannot be in doubt.

Cecil, I don't believe the outcome is in doubt.

Walt

Walter Maxwell wrote:
But you
can see from my words above that voltage rules--when the voltages are 180 out of
phase it defines a short circuit.

This is exactly the same mistake that Dr. Best made. *VOLTAGE DOESN'T RULE!*
Current is *equally* important to voltage. If you had assumed that "current
rules", you would be saying - "when the currents are 180 out of phase it
defines an open circuit".

My argument is actually a minor point but bridges part of the gap between
you and Dr. Best. (And absolutely nothing being discussed here concerns
the source impedance of a transmitter. All we are discussing is what
happens at a match point in a transmission line or at a tuner.)
--
73, Cecil http://www.qsl.net/w5dxp



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On Sat, 05 Jun 2004 19:20:18 -0500, Cecil Moore wrote:

Walter Maxwell wrote:
But you
can see from my words above that voltage rules--when the voltages are 180 out of
phase it defines a short circuit.

This is exactly the same mistake that Dr. Best made. *VOLTAGE DOESN'T RULE!*
Current is *equally* important to voltage. If you had assumed that "current
rules", you would be saying - "when the currents are 180 out of phase it
defines an open circuit".

Then how can you explain what happens when you reverse the zip cord, plugging
one end in one way and the other with the prongs reversed ? Are you saying the
currents in this condition are seeing an open circuit?

My argument is actually a minor point but bridges part of the gap between
you and Dr. Best. (And absolutely nothing being discussed here concerns
the source impedance of a transmitter. All we are discussing is what
happens at a match point in a transmission line or at a tuner.)

Walter Maxwell wrote:
Then how can you explain what happens when you reverse the zip cord, plugging
one end in one way and the other with the prongs reversed ? Are you saying the
currents in this condition are seeing an open circuit?

I'm sorry, Walt, you lost me. What zip cord?
--
73, Cecil http://www.qsl.net/w5dxp



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On Sat, 05 Jun 2004 23:39:35 -0500, Cecil Moore
wrote:
What zip cord?
:-)
A point offered that is not even half a day old... Symptoms of two
conversations running under the impression they are on the same
planet.

On Sat, 05 Jun 2004 23:39:35 -0500, Cecil Moore wrote:

Walter Maxwell wrote:
Then how can you explain what happens when you reverse the zip cord, plugging
one end in one way and the other with the prongs reversed ? Are you saying the
currents in this condition are seeing an open circuit?

I'm sorry, Walt, you lost me. What zip cord?

Cecil, you must not be reading my posts. Go back one or two to get the drift.

Walt

Walter Maxwell wrote:
Cecil Moore wrote:

Walter Maxwell wrote:
Then how can you explain what happens when you reverse the zip cord, plugging
one end in one way and the other with the prongs reversed ? Are you saying the
currents in this condition are seeing an open circuit?

I'm sorry, Walt, you lost me. What zip cord?

Cecil, you must not be reading my posts. Go back one or two to get the drift.

Are you talking about the two generators hooked up back to back.
If so, where are the two EM waves traveling in the same direction
which is a prerequisite for complete destructive/constructive
interference? The generated EM waves, in your example, are moving
in opposite directions which is simply not relevant to this discussion.

Please conjure up an experiment where two coherent waves are
moving in the same direction without affecting the generators.
--
73, Cecil http://www.qsl.net/w5dxp



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