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

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

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

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

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

Jim Kelley wrote:
Cecil Moore wrote:

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.

Indeed.

I measured current, which as everyone with a Novice or higher grade
license should know is the rate of flow of charge(*). The charge flows
in one direction during each half cycle, and in the other during the
other half cycle, resulting in current which is positive for half the
cycle and negative for the other. This is known as "alternating
current". In fact, my measurement system (ferrite core transformers)
will only detect alternating current.

(*)We very commonly, although technically incorrectly, refer to "current
flow" when we really mean "charge flow".

Roy Lewallen, W7EL

Roy Lewallen wrote:
I measured current, which as everyone with a Novice or higher grade
license should know is the rate of flow of charge(*). The charge flows
in one direction during each half cycle, and in the other during the
other half cycle, resulting in current which is positive for half the
cycle and negative for the other. This is known as "alternating
current". In fact, my measurement system (ferrite core transformers)
will only detect alternating current.

Roy, you once verified that the phase of the total current
on a 1/2WL dipole changes by less than 10 degrees over the
entire 180 degree length of antenna. How can you use a current
that changes phase by only 10 degrees in 180 degrees of antenna
to measure the delay along the wire? If you cannot do it along
a wire, what makes you think you can do it through a loading
coil.

For the readers who don't know, Roy absolutely refuses to answer
any of my questions like the above.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

Roy Lewallen wrote:
I measured current, which as everyone with a Novice or higher grade
license should know is the rate of flow of charge(*). The charge flows
in one direction during each half cycle, and in the other during the
other half cycle, resulting in current which is positive for half the
cycle and negative for the other. This is known as "alternating
current". In fact, my measurement system (ferrite core transformers)
will only detect alternating current.

Looking at only one current sample point, one cannot tell
the difference between standing waves and traveling waves.
However, there is a large difference between standing waves
and traveling waves.

If you measure the same current phase at two sample points
that are physically 30 degrees apart, you are dealing with
standing waves.

The equation for a standing wave is of the form:

I = Imax*cos(bz)*cos(wt)

This current is the primary effect on a standing wave
antenna and cannot be used to measure the delay between
points in an antenna because this current does not change
phase relative to length 'z'.

If you measure a 30 degree phase shift in the current
between two sample points that are 30 degrees apart,
you are dealing with traveling waves.

The equation for a traveling wave is of the form:

I = Imax*cos(wt-bz)

This current is a secondary effect on a standing wave
antenna. This is the current that changes phase with
physical length 'z' but is swamped out by the standing
wave.

Roy, you listed three possibilities for people who
read your postings.

1. Those who agree with you and are therefore right.

2. Those who disagree with you and later change their
minds to being right.

3. Those who forever disagree with you and are therefore
forever wrong.

Please consider the 4th possibility.

4. Roy Lewallen is not omniscient and could possibly
be wrong.

Again, would someone please forward this to Roy since
he has plonked me?
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

Roy Lewallen wrote:
I measured current, which as everyone with a Novice or higher grade
license should know is the rate of flow of charge(*). The charge flows
in one direction during each half cycle, and in the other during the
other half cycle, resulting in current which is positive for half the
cycle and negative for the other.

Actually, electrons in a wire are slow-moving particles
and tend to oscillate back and forth at RF frequencies
rather than "flowing".

But what is being discussed here is the total current
reported by EZNEC. Is EZNEC wrong when it indicates
1 degree of current phase shift in 30 degrees of
length in a dipole antenna?
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

Jim Kelley wrote:
Cecil Moore wrote:
It's *energy* in the traveling wave that gets radiated.
Less energy indeed lowers the current amplitude.

Agreed.

Note that we agree on almost everything.

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. ... I've said my piece.

Exactly, the more you post, the more obvious agreements
we have. The following current is the one that dominates
a standing-wave antenna.

I(x,t) = Imax*cos(kx)*cos(wt)

Such a current cannot be used to calculate delay from
phase shift in a wire or in a coil. Yet, that is exactly
what w7el and w8ji did.

Are you leaving the thread because you are on the verge
of proving w7el wrong?
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com