Standing morphing to travelling waves, and other stupid notions
 

On Jan 10, 7:02 pm, Roy Lewallen wrote:
Wouldn't it be fun to calculate the power in each of the infinite number
of sine waves and add them together like Cecil does to get the total
power?

Optical scientists have been "adding" EM wave power densities for
centuries using the irradiance equation which includes the phase angle
between the E-fields. I'm surprised you are still ignorant of that
fact of physics.
--
73, Cecil, w5dxp.com

Standing morphing to travelling waves, and other stupid notions
 

On Thu, 10 Jan 2008 17:35:42 -0800 (PST), Cecil Moore
wrote:

dipole standing waves are only about

Ah, yes! The devil is in the "about" where Cecil can prove a new
fundamental law with errors of only 50%. Naturally, we will have to
subscribe to newsletters to find the data. Let me anticipate the next
burst of evidence:
"But you MUST admit that 1 amp through 1 ohm is 1 volt.
Denying this makes you a liar!"

73's
Richard Clark, KB7QHC

Standing morphing to travelling waves, and other stupid notions
 

Cecil Moore wrote:

I don't remember saying that and I apologize if I ever did. What I
remember saying is that an RF standing wave doesn't meet the
definition of an EM wave which is essentially the same thing that Dr.
Hecht said: "Standing Waves:....These might better not be called waves
at all since they do not transport energy and momentum."

You could shortcut the whole process and just have Dr. Hecht post his
ideas here instead. I bet ya anything there would be far fewer
arguments about physics. :-)

RF standing waves, unlike other EM waves, do not transport energy and
momentum at the speed of light in the medium. Therefore, they are
technically not EM (photonic) waves.

Technically, they're just spatial interference patterns, so of course
they don't propagate energy. They're like any other spatial
interference pattern in that regard.

ac6xg

Standing morphing to travelling waves, and other stupid notions
 

Cecil Moore wrote:

On Jan 10, 2:25 pm, Jim Kelley wrote:

So much for the Poynting vector of a position envelope. What are your
thoughts regarding the Poynting vector for a time varying envelope of
an electromagnetic wave? :-)


If the wire runs in the 'x' direction, the standing wave phasors
rotate only in the 'yz' plane.

A standing wave is an amplitude vs position envelope. An amplitude vs
time envelope is modulation! :-)

ac6xg

Standing morphing to travelling waves. was r.r.a.a Laugh Riot!!!
 

On Jan 9, 10:46*pm, Cecil Moore wrote:
On Jan 9, 3:33 pm, Gene Fuller wrote:
Reflections *ARE* power factor problems. When the power company brings
the power factor to unity, they have eliminated reflections and turned
the system into a traveling wave energy delivery system.

This would not be quite correct. The power factor correction
capacitors make the load impedance real, they do not match
the load to the impedance of the distribution line. As such,
they have not eliminated reflections.

Since the customer decides on the load impedance (infinity
when the equipment is disconnected), the power company is
always dealing with mismatched loads. And does not seem
too concerned as long as the load is close to real.

It might be instructive to consider some real transmission
systems. From La Grande-2 (5.6 GW) or Churchill Falls (5.4 GW)
to the first significant load center is about 1/4 wave
at 60 Hertz. Churchill Falls has three 735 kV lines to move
the energy; 1.8 GW per line. At 735 kV, that's about a
300 ohm load impedance. I've seen estimates that put power
line impedance between 100 and 400 ohms. So there might be
a match at full load, but at no load there is serious
mismatch. Of course the generator impedance is close
to zero (feedback achieves this) so there is no attempt
to match at that end. (The above quick analysis ignores
that it is actually a three phase system).

There are apparently serious challenges with keeping
the output voltage down on lightly loaded lines (q.v.
Ferranti effect).

And what happens when the load breakers at the end of
the line trip. 4 milliseconds later the reflected wave
arrives back at the plant. What happens when it hits
the 0 output impedance of the generators?
And how does one stop 11 columns of water 1000 feet
high (500 psi) and 20 feet in diameter before the
generators overspeed?

I am betting there is a story there.

...Keith

Standing morphing to travelling waves, and other stupid notions
 

On Jan 10, 9:23 pm, Jim Kelley wrote:
A standing wave is an amplitude vs position envelope.

Sorry, that is a false statement. Please reference "Fields and Waves
in Communication Electronics" by Ramo, Whinnery, and Van Duzer, page
343. The equation for the standing wave voltage is: Ez = Efor*e^j(wt-
Bz) + Eref*e^j(wt+Bz)

The equation for a standing wave *envelope* does not contain an
(omega*t) term. The equation for the *standing wave* indeed does
obviously contain (omega*t) terms since the equation for a standing
wave is the sum of the two component traveling waves each containing
an (omega*t) term.

If the (omega*t) term is omitted it is an envelope equation, not a
wave equation.
--
73, Cecil, w5dxp.com

Standing morphing to travelling waves, and other stupid notions
 

On Jan 10, 8:54 pm, Jim Kelley wrote:
Technically, they're just spatial interference patterns, so of course
they don't propagate energy. They're like any other spatial
interference pattern in that regard.

Thus Hecht's suggestion that they don't deserve to be called waves. I
think they should be called illusionary waves.
--
73, Cecil, w5dxp.com

Standing morphing to travelling waves. was r.r.a.a Laugh Riot!!!
 

On 9 Jan, 19:59, Cecil Moore wrote:
On Jan 9, 7:48 pm, art wrote:

Thus it is the length of the antenna by your statement is what turns
around the current regardless of the frequency applied.

The feedpoint impedance of these standing wave antennas can be closely
approximated by

Zfp = (Vfor+Vref)/(Ifor+Iref)

where all values are phasors. For instance, the reflected voltage will
be out of phase with the forward voltage at the feedpoint for a
resonant 1/2WL dipole while the reflected current will be in phase
with the forward current. The feedpoint impedance of a 1/2WL dipole is
very close to (|Vfor|-|Vref|)/(|Ifor|+|Iref|). See if you can figure
it out for other lengths of dipoles.
--
73, Cecil, w5dxp.com

We haven't moved forward a bit on that first sentence of the other
post
which is " what created the reflecting voltage" of this resonant
radiator
when it is a fractional wavelength or a electrically full wave length?
Since I am interested in a time varying current for propagation why
should I
worry about anything else ?
Art

Standing morphing to travelling waves, and other stupid notions
 

"AI4QJ" wrote in message
...
and add them together like Cecil does to get the total power? Boy, I'll
bet you'd have a *lot*!

I'm sorry but this taunt rings a little hollow...it just isn't funny
because you can/will get a finite number for power.


its called the Dirac delta function. and infinitely narrow, infinitely
high, single pulse that contains finite energy... the Fourier spectrum of it
includes frequencies from zero to infinity which extend in time from
negative infinity to positive infinity... the function that doesn't exist,
yet has influence across all time and has infinite numbers of uses when
analyzing circuits even though no one can generate it.

Standing morphing to travelling waves. was r.r.a.a Laugh Riot!!!
 

On Jan 10, 10:24 pm, Keith Dysart wrote:
The power factor correction
capacitors make the load impedance real, they do not match
the load to the impedance of the distribution line. As such,
they have not eliminated reflections.

It's a little more complicated than that. If the voltage and current
are actually brought into phase all along the transmission line, the
system is indeed a traveling wave system free of reflections. If the
power factor is exactly 1.0 at all points up and down the line, the
line is flat, i.e. matched by definition. Of course, it's not a
perfect system and the power factor is rarely exactly 1.0 so the
system usually exhibits signs of a mismatch, an overhead expense for
the power company.
--
73, Cecil, w5dxp.com