Dish reflector
 

Jim Kelley wrote:
I understand it well enough to note that it fails to make your point for
you.

You obviously don't understand why a signal that doesn't
change phase cannot be used to measure a delay based
on phase shift either through a wire or a coil.

1. Every reference says a pure standing wave does not
change phase.

2. The current on a 75m mobile antenna is at least 90%
standing wave current.

3. Therefo The phase of the current on a 75m mobile
antenna cannot be used to measure the delay through
the loading coil or even through the straight wire
parts of the antenna.

4. Yet, this is exactly the current that w7el and w8ji
used in their measurements which yielded "no detectable
phase shift" completely unrelated to delay.

Here's a question for you: What is the phase shift
in the current in 90 degrees of an ideal lossless
1/4WL stub? Until you can provide a valid direct
answer to that direct question, you will never
understand.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

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Cecil Moore wrote:

If that will keep your panties from getting bunched
up, I am all for it.

I'd really prefer that you refrained from commenting about my underwear
- or even thinking about them. :-)

ac6xg

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Cecil Moore wrote:
Jim Kelley wrote:
I understand it well enough to note that it fails to make your point
for you.

You obviously don't understand why a signal that doesn't
change phase cannot be used to measure a delay based
on phase shift either through a wire or a coil.

1. Every reference says a pure standing wave does not
change phase.

Certainly not as a function of time. Which means it's not an
alternating current, and which is why it not considered an actual wave.

2. The current on a 75m mobile antenna is at least 90%
standing wave current.

And what's the other 10% supposed to be? Please explain how one would
go about getting "standing wave current" to flow through something -
anything - like a measuring instrument for example.

3. Therefo The phase of the current on a 75m mobile
antenna cannot be used to measure the delay through
the loading coil or even through the straight wire
parts of the antenna.

Have you tried pulsing a current through one? I can't imagine there
wouldn't be a delay in getting from one end to the other and back.

4. Yet, this is exactly the current that w7el and w8ji
used in their measurements

No, it is not.

Here's a question for you: What is the phase shift
in the current in 90 degrees of an ideal lossless
1/4WL stub?

I'm reminded of the troll at the bridge.

To what phase shift do you refer? With respect to voltage, from one
point to another, out and back - you need to be considerably less
imprecise if you expect someone to bother to answer (to) you.

ac6xg

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Jim Kelley wrote:
A standing wave interference pattern is a result of the presence
of traveling waves. One does not replace the other.

Exactly what I have been saying for years against some
stiff opposition - welcome aboard.

You missed the point which is: If one parses all the energy
to the standing wave, it cannot separately be parsed to the
traveling waves. Doing so would violate the conservation
of energy principle.

I you were producing numbers which made sense and were correct, we
wouldn't be having this discussion, Cecil. A wave is at various phases
along it's length. The phase varies from 0 to 360 every complete cycle.
This includes standing waves. Its phase is not "zero" at every point.

You obviously don't understand. Whatever the actual phase
angle is, for a pure standing wave, at any instant of time,
it is constant all up and down the standing wave. NOBODY HAS
EVER SAID IT IS ZERO AT EVERY POINT!!! Such an allegation is
a ridiculous blowing of smoke.

The
EZNEC results you refer to are an archetypal example of the effect.

The EZNEC results are what they are and have been confirmed
by w7el himself. All I can say is: Please correct your mistaken
concepts and then rejoin the discussion. What is it about the
following EZNEC results that you don't understand? Do you need
help in comprehending that a 2.71 degree phase shift in 90 degrees
of antenna is a shortfall of 87.29 degrees?

EZNEC+ ver. 4.0
thin-wire 1/4WL vertical 4/17/2009 2:57:42 PM
--------------- CURRENT DATA ---------------
Frequency = 7.29 MHz
Wire No. 1:
Segment Conn Magnitude (A.) Phase (Deg.)
1 Ground 1 0.00
2 .97651 -0.42
3 .93005 -0.83
4 .86159 -1.19
5 .77258 -1.50
6 .66485 -1.78
7 .54059 -2.04
8 .40213 -2.28
9 .25161 -2.50
10 Open .08883 -2.71

If w7el "measures" the phase shift between segment 3
and segment 7, he will "measure" 1.21 degrees. The actual
delay between segment 3 and segment 7 is about 36 degrees.
When will anyone understand that fact of physics?
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

Dish reflector
 

Jim Kelley wrote:
2. The current on a 75m mobile antenna is at least 90%
standing wave current.

And what's the other 10% supposed to be?

The other 10% is the traveling wave that gets radiated
of course (neglecting losses).

Please explain how one would
go about getting "standing wave current" to flow through something -
anything - like a measuring instrument for example.

Opps, standing wave current doesn't flow so you must
have meant how does one eliminate reflections so that
nothing except traveling wave current is present.
Do you need that explained to you?

Have you tried pulsing a current through one? I can't imagine there
wouldn't be a delay in getting from one end to the other and back.

Exactly, but some would say that's digital, not RF,
or that is not steady-state conditions.

4. Yet, this is exactly the current that w7el and w8ji
used in their measurements

No, it is not.

Sorry, you are wrong about that. w7el described in detail
what he had measured and it was "total current" which was
about 90% standing wave current. Here's what he said:

"The result from the second test was a current difference
of 5.4%, again with no measurable phase shift." All using
the total antenna current which is about 90% standing
wave current. What he didn't realize is that a current
difference of 5.4% is a calculated phase shift of ~19
degrees, i.e. ARCCOS(1-.054) = ~19 degrees, to which
you have previously alluded.

Here's a question for you: What is the phase shift
in the current in 90 degrees of an ideal lossless
1/4WL stub?

I'm reminded of the troll at the bridge.

I'm reminded of people who refuse to answer simple questions.
One wonders why? The answer is zero degrees.

To what phase shift do you refer? With respect to voltage, from one
point to another, out and back - you need to be considerably less
imprecise if you expect someone to bother to answer (to) you.

The context was specified as current. Here is an EZNEC simulation
which should help you.

http://www.w5dxp.com/stub_dip.EZ

Click on currents. You will see that the current phase
varies by ~2 degrees end to end in 90 degrees of stub
just as it does in a 1/4WL monopole over ground.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

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Cecil Moore wrote:
The other 10% is the traveling wave that gets radiated
of course (neglecting losses).

Absurd. Current does not "get radiated".

Please explain how one would go about getting "standing wave current"
to flow through something - anything - like a measuring instrument for
example.

Opps, standing wave current doesn't flow so you must
have meant how does one eliminate reflections so that
nothing except traveling wave current is present.
Do you need that explained to you?

You claim that W7EL measured the phase shift of standing wave current.
He of course made no such claim. So yes, I need you to explain how it
is possible for someone do measure a "current" that does not flow. This
should be good.

ac6xg

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Jim Kelley wrote:
Cecil Moore wrote:
The other 10% is the traveling wave that gets radiated
of course (neglecting losses).

Absurd. Current does not "get radiated".

It's *energy* in the traveling wave that gets radiated.
Less energy indeed lowers the current amplitude.

The Method Of Moments used by NEC assumes the radiated
fields originate from the current in each segment of
the antenna. Current is certainly attenuated by radiation
as it is by dissipation in lossy transmission lines. In
fact, the same attenuation factor is applied to the current
equation as is applied to the voltage equation.

The difference in the forward current vs the reflected
current on the standing-wave antenna at the antenna feedpoint
is due to energy lost to radiation. Radiation from an antenna
indeed does lower the current on the antenna. The conservation
of energy principle strikes again.

You can prove it for yourself by modeling a terminated rhombic
using EZNEC. The current amplitude in the traveling wave
antenna slowly falls as the energy is radiated.

Or put in one amp of 70cm current at one end of 200 feet of
RG-58 and see how much current you get out at the other end.

You don't really think that lumped circuit model assumptions
apply to distributed networks, do you?

You claim that W7EL measured the phase shift of standing wave current.
He of course made no such claim. So yes, I need you to explain how it
is possible for someone do measure a "current" that does not flow. This
should be good.

My point exactly. w7el "measured" the phase shift in current
that doesn't flow. That was his entire problem. One cannot
measure phase shift in current that doesn't flow, yet that's
exactly what w7el and w8ji reported doing.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

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Cecil Moore wrote:
Jim Kelley wrote:
Cecil Moore wrote:
The other 10% is the traveling wave that gets radiated
of course (neglecting losses).

Absurd. Current does not "get radiated".

It's *energy* in the traveling wave that gets radiated.
Less energy indeed lowers the current amplitude.

Agreed. But when discussing current, one should recognize that, with
the exception of "non-flowing current" whatever that is, all currents
produce a field. Field cancellation is what prevents the transfer of
energy. Any of this sounding familiar to you? The standing wave
pattern is useful for illustrating what the field interference pattern
might look like.

w7el "measured" the phase shift in current
that doesn't flow.

:-) He's good, but he ain't that good. Besides, his meter is the same
as yours in that it only responds to waves that travel and currents that
flow. The difference I suspect, is in the desired outcome and the
rhetoric.

I've said my piece.

73, ac6xg

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Jim Kelley wrote:

You claim that W7EL measured the phase shift of standing wave current.
He of course made no such claim. So yes, I need you to explain how it
is possible for someone do measure a "current" that does not flow. This
should be good.

I measured current (of which the definition is well understood except
apparently by Cecil), and took a lot of care to do it right. Cecil
doesn't like the result, so he's created an imaginary quantity he calls
"standing wave current" as an attempt to invalidate the results and
promote his imaginative theories. Since it's wholly his creation, its
properties are free to be modified as the immediate argument requires.

As I, Jim, other posters, and all good texts have explained, a standing
wave describes the amplitude envelope of a voltage or current, as a
function of position, which results from interference between traveling
waves. There's no such thing as "standing wave current". You'll find no
references to this fictitious entity in any electromagnetics text.

Roy Lewallen, W7EL

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"Art Unwin" wrote in message
...
On Apr 16, 9:48 pm, Cecil Moore wrote:

I don't worry about it Cecil but I am concerned at the number of
people who consider themselves engineers. Remember that nobody on this
group has a true understanding of Maxwells equations! Nobody has
proved Maxwell's laws can be proved by adding a time varing field to
the Gaussian law of Statics. In fact, it is denied by ALL on this
group, Engineers?

yes art, electrical engineers, like me, do understand maxwell's equations.
and any of them worth their salt will explain, like i have done many times,
that it is unecessary to add an explicit time variable to the equations
because they are valid at every instant of time... so you end up with
f(t)=f(t) which is redundant and doesn't help with the solution of the
fields and waves. you have admitted that you don't know fields and waves
and that you are not an ee, yet you continue to try to put down those who
show a true understanding of the equations and their underlying assumptions.
you further demonstrate this by talking about lumped impedances in reference
to maxwell's equations and antennas. maxwell's equations describe fields
and waves, not the conductors and elements that generate them. they
reference the currents and fields, not the wires, capacitors, and inductors.
you can derive the properties of inductors and capacitors from maxwell's
equations, but you have to look deep inside them and apply the basic laws
that make up maxwell's equation to describe the lumped elements.

you have yet to explain where equilibrium is required in maxwell's
equations. by definition they rely on non-equilibrium conditions to set up
waves. you can't have a wave while you are in equilibrium, something has to
be putting energy into the system and something has to be moving, that
sounds like non-equilibrium to me.