On Mar 16, 11:39*pm, Owen Duffy wrote:
Hi Tom,

K7ITM wrote :

...

I'm sorry...perhaps I don't understand your notation. *Don't you

I am taking a convention that the sense of currents in segments is from
bottom to top. That means that I defined all segments in order from bottom
to top.

My notation ~= is to mean approximately equal.

Does that clarify things?

Cheers
Owen

Yes--and then if they were exactly equal, would that not imply only
transmission line current on the stub? Obviously, they are exactly
equal if you simply connect the ends of the elements together...but
that isn't what gets us to in-phase currents at the centers of each
element (in the case of the symmetrical 3 element design; or the base
current in the bottom quarter wave in phase with the center current in
the top half wave...), and (nearly) equal currents at those current
maxima. To the extent that the currents A and D in your diagram
differ, there is common-mode or "antenna" current on the stub.

Cheers,
Tom

K7ITM wrote in
:

....
Yes--and then if they were exactly equal, would that not imply only
transmission line current on the stub? Obviously, they are exactly

Thinking some more about it, my current thinking is that my analysis was
flawed. I was using the standing wave currents, when I should be using
the travelling wave components.

I suspect that when NEC models the conductor arrangement at my fig a), it
correctly accounts for propagation delay and the phase relationships
compute correctly.

If we replace the stub with a TL element, I suspect that NEC reduces the
TL to a two port network and loads a segment of the vertical with an
equivalent steady state impedance of the s/c stub network. If that is
done, the reduction to a lumped load means that there is zero delay to
travelling waves, and the computed currents (amplitude and phase) in the
vertical will be incorrect. This means that you cannot replace a resonant
stub with a high value of resistance, it doesn't work.

If that is the case, it suggests that NEC cannot model such phasing
schemes using TL elements.

Owen

Owen Duffy wrote:
Thinking some more about it, my current thinking is that my analysis was
flawed. I was using the standing wave currents, when I should be using
the travelling wave components.

That's exactly the flaw committed by w8ji and w7el when
they tried to measure the delay through a 75m loading
coil using standing wave current which doesn't appreciably
change phase through a loading coil or through the entire
90 degree length of a monopole. Using standing wave
current, w8ji measured a 3 nS delay through a 10 inch
long coil, a VF of 0.27.

http://www.w8ji.com/inductor_current_time_delay.htm

W7EL reported: "I found that the difference in current
between input and output of the inductor was 3.1% in
magnitude and with *no measurable phase shift*, despite
the short antenna... The result from the second test was
a current difference of 5.4%, again with *no measurable
phase shift*."

Of course, phase shift is not measurable when one is
using standing wave current with its almost unchanging
phase. EZNEC supports that assertion. Bench measurements
support that assertion.

When traveling waves are used to measure the delay through
a 75m loading coil, the correct delay through w8ji's 10
inch coil turns out to be about 26 nS (~37 degrees) at 4 MHz
with a more believable VF of 0.033.

http://www.w5dxp.com/current2.htm
--
73, Cecil http://www.w5dxp.com
"Government 'help' to business is just as disastrous as
government persecution..." Ayn Rand

Cecil Moore wrote:
Owen Duffy wrote:
Thinking some more about it, my current thinking is that my analysis
was flawed. I was using the standing wave currents, when I should be
using the travelling wave components.

That's exactly the flaw committed by w8ji and w7el when
they tried to measure the delay through a 75m loading
coil using standing wave current which doesn't appreciably
change phase through a loading coil or through the entire
90 degree length of a monopole. Using standing wave
current, w8ji measured a 3 nS delay through a 10 inch
long coil, a VF of 0.27.

http://www.w8ji.com/inductor_current_time_delay.htm

W7EL reported: "I found that the difference in current
between input and output of the inductor was 3.1% in
magnitude and with *no measurable phase shift*, despite
the short antenna... The result from the second test was
a current difference of 5.4%, again with *no measurable
phase shift*."

Of course, phase shift is not measurable when one is
using standing wave current with its almost unchanging
phase. EZNEC supports that assertion. Bench measurements
support that assertion.

When traveling waves are used to measure the delay through
a 75m loading coil, the correct delay through w8ji's 10
inch coil turns out to be about 26 nS (~37 degrees) at 4 MHz
with a more believable VF of 0.033.

http://www.w5dxp.com/current2.htm

Cecil, if I ever have a dead horse on my hands, I won't let you
near it because you'll beat it even deader.
73,
Tom Donaly, KA6RUH

Tom Donaly wrote:
Cecil, if I ever have a dead horse on my hands, I won't let you
near it because you'll beat it even deader.

The horse is alive and well - the nonsense that I quoted
is still on W8JI's web page.
--
73, Cecil http://www.w5dxp.com
"Government 'help' to business is just as disastrous as
government persecution..." Ayn Rand

Cecil Moore wrote:
Owen Duffy wrote:
Thinking some more about it, my current thinking is that my analysis
was flawed. I was using the standing wave currents, when I should be
using the travelling wave components.

That's exactly the flaw committed by w8ji and w7el when
they tried to measure the delay through a 75m loading
coil using standing wave current which doesn't appreciably
change phase through a loading coil or through the entire
90 degree length of a monopole. Using standing wave
current, w8ji measured a 3 nS delay through a 10 inch
long coil, a VF of 0.27.

http://www.w8ji.com/inductor_current_time_delay.htm

W7EL reported: "I found that the difference in current
between input and output of the inductor was 3.1% in
magnitude and with *no measurable phase shift*, despite
the short antenna... The result from the second test was
a current difference of 5.4%, again with *no measurable
phase shift*."

Of course, phase shift is not measurable when one is
using standing wave current with its almost unchanging
phase. EZNEC supports that assertion. Bench measurements
support that assertion.

When traveling waves are used to measure the delay through
a 75m loading coil, the correct delay through w8ji's 10
inch coil turns out to be about 26 nS (~37 degrees) at 4 MHz
with a more believable VF of 0.033.

http://www.w5dxp.com/current2.htm

I agree that electromagnetic traveling waves are the kinds of waves that
propagate on and cause radiation to emanate from an antenna. But your
claims about 'standing waves not changing phase along the antenna'
provoke the following questions:

1.) what relation (if any) do you believe the wavelength of the standing
wave has to the wavelength of the radio frequency waves traveling on an
antenna? And,

2.) what relation (if any) does the phase of a sinusoidal wave have to
its amplitude?

73, ac6xg

Jim Kelley wrote:
I agree that electromagnetic traveling waves are the kinds of waves
that propagate on and cause radiation to emanate from an antenna. But
your claims about 'standing waves not changing phase along the antenna' ...

Jim, I thought you have EZNEC. Here are the currents at all of
the segments along a 20m dipole with 21 segments from end to end.
Please note that in a dipole that is 180 degrees long, the phase
of the (mostly standing-wave) current varies by less than 3 degrees.
How can the current in a 180 degree antenna vary by less than 3 degrees?

Quoting my web page: "Standing wave current cannot be used to directly
measure either a valid amplitude change or a valid phase shift through
a loading coil. All of the reported conclusions based on loading coil
measurements using standing-wave current on standing-wave antennas are
conceptually flawed." Owen had an epiphany of a sort when he realized
that fact of physics.

20m dipole 3/18/2009 5:28:50 PM

--------------- CURRENT DATA ---------------

Frequency = 14.2 MHz

Wire No. 1:
Segment Conn Magnitude (A.) Phase (Deg.)
1 Open .0836 -2.75
2 .23595 -2.57
3 .37707 -2.38
4 .50791 -2.17
5 .62692 -1.95
6 .73226 -1.71
7 .82218 -1.44
8 .89511 -1.13
9 .94979 -0.78
10 .98539 -0.37
11 1 0.00
12 .98539 -0.37
13 .94979 -0.78
14 .89511 -1.13
15 .82218 -1.44
16 .73226 -1.71
17 .62691 -1.95
18 .50791 -2.17
19 .37707 -2.38
20 .23595 -2.57
21 Open .0836 -2.75
--
73, Cecil http://www.w5dxp.com
"Government 'help' to business is just as disastrous as
government persecution..." Ayn Rand

P.S. I posted this reply but it didn't show up on my server.
I apologize if it is a duplicate.

Cecil Moore wrote:
Jim Kelley wrote:
I agree that electromagnetic traveling waves are the kinds of waves
that propagate on and cause radiation to emanate from an antenna. But
your claims about 'standing waves not changing phase along the antenna'
...

Jim, I thought you have EZNEC.
Here are the currents at all of
the segments along a 20m dipole with 21 segments from end to end.
Please note that in a dipole that is 180 degrees long, the phase
of the (mostly standing-wave) current varies by less than 3 degrees.
How can the current in a 180 degree antenna vary by less than 3 degrees?

It seems to me that computers are completely stupid about certain
things. Could it be a case of garbage in, garbage out?

Quoting my web page: "Standing wave current cannot be used to directly
measure either a valid amplitude change or a valid phase shift through
a loading coil. All of the reported conclusions based on loading coil
measurements using standing-wave current on standing-wave antennas are
conceptually flawed."

And what more authoritative reference could someone cite than their own
web page? :-)

I've never actually known what it was that made you believe Roy had
measured standing wave current - whatever that means. Or, how his
measurements compare with your own measurements of the phenomenon.

Owen had an epiphany of a sort when he realized
that fact of physics.

It may not even be as elusive a fact as one is given to believe around here.

73, ac6xg



20m dipole 3/18/2009 5:28:50 PM

--------------- CURRENT DATA ---------------

Frequency = 14.2 MHz

Wire No. 1:
Segment Conn Magnitude (A.) Phase (Deg.)
1 Open .0836 -2.75
2 .23595 -2.57
3 .37707 -2.38
4 .50791 -2.17
5 .62692 -1.95
6 .73226 -1.71
7 .82218 -1.44
8 .89511 -1.13
9 .94979 -0.78
10 .98539 -0.37
11 1 0.00
12 .98539 -0.37
13 .94979 -0.78
14 .89511 -1.13
15 .82218 -1.44
16 .73226 -1.71
17 .62691 -1.95
18 .50791 -2.17
19 .37707 -2.38
20 .23595 -2.57
21 Open .0836 -2.75

Jim Kelley wrote:
I've never actually known what it was that made you believe Roy had
measured standing wave current - whatever that means.

Good Grief! Could it be that a monopole is a "STANDING WAVE ANTENNA"?
--
73, Cecil http://www.w5dxp.com
"Government 'help' to business is just as disastrous as
government persecution..." Ayn Rand

Owen Duffy wrote:
K7ITM wrote in
:

...
Yes--and then if they were exactly equal, would that not imply only
transmission line current on the stub? Obviously, they are exactly

Thinking some more about it, my current thinking is that my analysis was
flawed. I was using the standing wave currents, when I should be using
the travelling wave components.

I suspect that when NEC models the conductor arrangement at my fig a), it
correctly accounts for propagation delay and the phase relationships
compute correctly.

If we replace the stub with a TL element, I suspect that NEC reduces the
TL to a two port network and loads a segment of the vertical with an
equivalent steady state impedance of the s/c stub network. If that is
done, the reduction to a lumped load means that there is zero delay to
travelling waves, and the computed currents (amplitude and phase) in the
vertical will be incorrect. This means that you cannot replace a resonant
stub with a high value of resistance, it doesn't work.

If that is the case, it suggests that NEC cannot model such phasing
schemes using TL elements.

Owen

Why would NEC reduce a TL two-port to a lumped load? Two-port
parameters can handle transmission line problems quite well without
the simplifying assumption that all components are of zero length.
73,
Tom Donaly, KA6RUH