W4JLE wrote:
One can NOT see a
standing wave, whereas one may be computed from the observations.

Standing waves are in fact the observable result of the superposition of
traveling waves. Interferometers are devices which function because of
the fact that standing wave interference patterns are observable. Radio
interferometers allow us to do radio astronomy with improved spacial
resolution. We most certainly can see standing waves.

73, Jim AC6XG

(Richard Harrison) wrote in message ...
Dr. Slick wrote:
"Err, Cecil, dQ/dt is zero at the voltage nodes."

dQ/dt is the rate of change in electrical charge with respect to time.

Charge moves in synch the applied voltage in a resistance. So, a
sinusoidal voltage node is a point in the cycle where the voltage has
zero amplitude, and so does the current. dQ/dt is hardly zero at zero
crossings of the a-c waveform.


It most certainly is. dQ/dt=0 at the voltage maxima and minima
(or the + and - peaks of the voltage).

Likewise, the voltage is always zero at the point where the peak
current occurs.

This is all assuming an infinity:1 mismatch, or full reflections.



S.

Cecil Moore wrote in message ...
Richard Harrison wrote:
Cecil is getting at the effective value of an a-c waveform which is rms.
Slick and Cecil are talking about two different things.

I was a little sleepy when I wrote that. It didn't occur to me until
later that Slick can also use dQ/dt = 0 over a complete cycle to prove
that the average value of any AC current is zero, not just at a voltage
node. Hence the necessity for RMS values for AC.


That's not what i meant. I mean that with full reflections, there
will be nodes space 1/2 wavelengths apart that will have 0 RMS AC
current. These points will coincide with the absolute peak voltages
that occur on the line.



If Slick can tell a forward wave from a traveling wave by taking one and
only one current measurement at one point on a transmission line, and
knowing nothing else about the system, he is a better man than I.


More of your TRULY confusing terminology! It really helps you
cloud the
argument, doesn't it! Unfortunately, if you don't understand someone,
it usually means they are full of sh**!

A forward wave is a traveling wave, traveling forward.

If you give me the Max RMS AC current, and the Min RMS current, i
can most certainly tell you what the SWR is.


S.

"Jim Kelley" wrote in message
...
W4JLE wrote:
One can NOT see a
standing wave, whereas one may be computed from the observations.

Standing waves are in fact the observable result of the superposition of
traveling waves. Interferometers are devices which function because of
the fact that standing wave interference patterns are observable. Radio
interferometers allow us to do radio astronomy with improved spacial
resolution. We most certainly can see standing waves.

73, Jim AC6XG

being able to 'see' them is how they got their name. you could run a neon
bulb or other voltage or current detector along an open wire line and 'see'
the standing wave voltage and current peaks and nulls... that was of course
in the days before they would have warned you to stay far, far away from
sources of rf exposure like that.

Dr. Slick wrote:
A forward wave is a traveling wave, traveling forward.

If you give me the Max RMS AC current, and the Min RMS current, i
can most certainly tell you what the SWR is.

That's two measurements which violates the challenge. Given one and
only one current reading, is the current traveling or standing? The
fact that you cannot tell the difference means the two currents possess
the same nature, i.e. magnitude, phase, and direction.
--
73, Cecil http://www.qsl.net/w5dxp



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Jim Kelley wrote:
So much for people who don't understand the difference between current
flow, and wave propagation. :-)

I've been talking about electron current flow, Jim, I don't recall
making any assertions about wave propagation. Waves and currents are
associated but are quite different things. Since the waves travel
at the speed of light, I assume photons are involved.
--
73, Cecil http://www.qsl.net/w5dxp



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Cecil wrote,

Jim Kelley wrote:


Cecil Moore wrote:
Here's what the standing
wave current looks like when it is not frozen in time. That's the topic of
discussion that everyone seems to want to avoid. Standing waves don't stand
still. They probably should have been called "looping waves".

http://einstein.byu.edu/~masong/HTMs...newave2EX.html

I guess that kind of thing can be exciting for the unitiated. Good for
you, Cecil!

So much for some people I know who assert, "Standing waves don't move." :-)
--
73, Cecil http://www.qsl.net/w5dxp


They change but they don't move.
73,
Tom Donaly

Cecil Moore wrote:

Waves and currents are
associated but are quite different things.

That's what I've been saying. Make sure you remember and apply that
concept when you're talking about 'direction'.

73, Jim AC6XG

Tdonaly wrote:
They change but they don't move.

Maybe it's relativity in action. The current stands
still and the earth moves around it?
--
73, Cecil http://www.qsl.net/w5dxp



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On 09 Feb 2004 20:28:28 GMT, (Tdonaly) wrote:
They change but they don't move.
73,
Tom Donaly

Gads Tom,

That will have him putting on his Galileo masquerade next. ;-)

I'm still waiting for that act where Cecileo drops his balls off the
Tower of Pisa.

I can anticipate the Cecilean logic now:
The balls, falling, traverse half the distance in half the time;
hence with each half of the remaining distance, half that time;
as there is always half the distance to go, they never hit;
ergo gravity does not exist!
If gravity does not exist, no test need be performed
(followed by 600 posts about the current in the Tiber).

[note: there is more than one error in this; however, I would just as
soon see which of his balls drops the farthest even if they don't hit
the ground.]

73's
Richard Clark, KB7QHC