RadioBanter - View Single Post

March 14th 06, 08:37 PM posted to rec.radio.amateur.antenna

wrote:
1.) RF current can stand still, yet cause current in a transformer
secondary.

Please provide a technical response to the following.

Hecht, in "Optics" says of standing waves of light in space:
"Its profile *DOES NOT MOVE* through space; it is clearly not
of the form f(x+vt). At any point x = x', the amplitude is a
constant equal to 2Eot*sin(kx') and E(x',t) [the electric
field] varies harmonically as cos(wt)." page 289, 4th edition.

The 'z' movement for a standing wave current magnitude
along a wire is completely divorced from the frequency of
the wave. Its profile *DOES NOT MOVE* through the wire.
Same as light standing waves above. It is not of the
form f(z+wt).

Since standing waves of light in space do not move, why is it
surprising that standing waves of RF on a wire do not move
for exactly the same reason since they have identical equations?
The standing wave energy in the H-field of RF standing waves
will certainly cause current in a transformer secondary just
as the standing wave light electric field will activate a
light detector.

2.) We have to use a "directional current coupler" to sort current
flowing one way from current flowing the other, because of standing wave
current.

There really may be humor in that statement which I never made.
I've never heard of a "directional current-only coupler". If
anyone knows of one, it sure would solve the measurement problem.

Anyone who knows how a directional coupler works is rolling around on
the floor laughing at the suggestion of sorting "forward current" from
"reflected current".

And I'm one of them. I've never said there existed such a device,
just that if it did exist, it would solve the measurement problem.
As it is, we haven't solved the measurement problem. The only means
I've seen of actually measuring the phase shift through a coil is
using the self-resonance method. Measuring the phase shift of
standing waves won't work because STANDING WAVES HAVE NO PHASE
SHIFT WHETHER THERE'S A COIL IN THE CIRCUIT OR NOT!

It appears this thread has reached the lowest level, where impossible
to build instrumentation is now demanded as the only acceptable proof.

It was a wish, not a demand. But we can indeed separate out the
forward wave from the reflected wave in a transmission line by
using a directional coupler calibrated for the Z0 of the line.
We can then carry those concepts over to a standing wave antenna,
according to Balanis.

So consider this experiment.

coil
source---50 ohm coax---X-////-Y---50 ohm coax---Load

We have directional couplers installed at 'X' and 'Y' and
we can in theory look at the phases of the forward and
reflected currents on each side of the coil. Will the
forward and reflected currents through the coil show
a phase shift or not? Seems we should start at a pretty
low frequency (low reactance) and work our way up. I
think the phase shift pattern would be clear.

Note that a cap to ground to the left of 'X' and a cap
to ground to the right of 'Y' would result in a pi-net
tuner. Wonder if there's any phase shift through the
coil in a pi-net tuner? Is a pi-net tuner a "phasing
network"?

How could the coil cause an arc on the Smith Chart
without changing the phase of the wave through the coil?
--
73, Cecil http://www.qsl.net/w5dxp