wrote:
I had this example at the bottom of my posting but you seem
to ignore such. So I am moving it to the top of the posting.
If you ignore it now, at least everyone will know you couldn't
possibly have missed it.
You are in a room with a 50 ohm transmission line routed
through a hole in one side of the room, across the room,
and through a hole in the other side of the room. You don't
know which is the source end of the line. A directional
wattmeter reads 200 watts forward power and 200 watts
reflected power but you don't know which direction is
forward. Here's a diagram:
200W-- 2 amps--
hole-------------------50 ohm coax-------------------hole
--200W --2 amps
Which direction is the standing wave current flowing?
If you knew forward current was moving left to right which
direction would the standing wave current be flowing?
That's not true at all Dave. Most of us know that current is current.
Too bad EZNEC disagrees with you as seen in the graphic at:
http://www.qsl.net/w5dxp/travstnd.GIF
The traveling wave current is virtually the opposite of the
standing wave current as can be seen by their different
equations. There is no phase information in the standing
wave current phase. Yet that is exactly the phase W7EL
used to try to measure the delay/phase shift through a
coil.
DC current is different from AC current. That's why the
DC or AC designations are necessary. RF forward current
is different from RF standing wave current. That's why
the different designations are necessary.
It really only flows one direction at any instant of time.
Or not at all at a standing wave current node.
Too bad we are talking RMS values here which is what EZNEC
reports. I'll ask the question of you: If one amp of RF
current is flowing in one direction and one amp of RF
current is flowing in the opposite direction, which direction
does the phasor sum of those two currents flow?
We can
indeed consider systems as having current that flows two directions at
one instant of time, but the results of that better agree with the
actual real current that flows only in one direction at any instant of
time or they are wrong.
The phase of standing wave current is unchanging. It doesn't "flow"
in the commonly accepted sense of the word. As Hecht says in "Optics":
"This is the equation for a STANDING or STATIONARY WAVE, as opposed
to a traveling wave. Its profile does not move through space; it is
clearly not of the form Func(x +/- vt)."
[Standing wave phase] "doesn't rotate at all, and the resultant
wave it represents doesn't progress through space - its a standing
wave."
If standing wave light doesn't move through space, then standing
wave RF also doesn't move through a wire.
(I assume we all
know current ... does not "drop", ...)
EM current does indeed drop exactly like EM voltage drops both
according to the attenuation factor. Just one more proof that
EM waves are not lumped circuit currents. The only difference
in the equation for transmission line voltage and current is
the voltage gets divided by the characteristic impedance which
is usually a resistive constant.
I think the basic problem is Cecil wants to used some definition of
current that does not allow models to be freely exchanged and does not
produce results that match real world systems. It always has to match.
We can't have different results unless someone has an error.
Exactly correct and the reason for the different results is your
error. In any conflict between the distributed network model and
the lumped circuit model, the distributed network model wins
every time since it is a superset of the lumped circuit model.
This has gone on for perhaps three years now. It is really up to Cecil
and Yuri to let it go, since they are the ones who seem to disagree
with measurements and accepted theory.
On the contrary, it is up to you and others to correct your
misconceptions about standing wave current. Your "accepted
theory" has holes in it that I could drive my GMC pickup
through.
--
73, Cecil
http://www.qsl.net/w5dxp