Cecil Moore wrote:

Please describe the pulse you intend to use on a
1/4WL long standing-wave antenna.

Kind of a wispy brunette one, about 5'7". What difference would it
make, Cecil? One that is short compared to the delay.

If the delay through the loading coil in a standing-
wave antenna could be measured in situ, then there
would not be any argument. But maybe I am missing
something. How would you propose to measure the delay
through a loading coil during steady-state for a
standing-wave antenna?

When you post a question in that way I gotta wonder what you must
think is going on inside an antenna. What's different about the
'situ' during steady state that causes electromagnetic fields to
propagate differently than at other times?

73, ac6xg

Jim Kelley wrote:
What difference would it
make, Cecil? One that is short compared to the delay.

What difference would it make if the frequency of the
pulse is far removed from the operating frequency?
What difference would it make if the frequency is far
above the self-resonant frequency? What difference
would it make if the inductance is completely
swamped by the capacitance? Shirley, you jest.

What's different about the 'situ' during
steady state that causes electromagnetic fields to propagate differently
than at other times?

They don't propagate differently but how does one separate
the forward wave from the reflected wave on a standing-wave
antenna? If you can do that, you will have solved the
measurement problem.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
Jim Kelley wrote:

What difference would it make, Cecil? One that is short compared to
the delay.


What difference would it make if the frequency of the
pulse is far removed from the operating frequency?
What difference would it make if the frequency is far
above the self-resonant frequency? What difference
would it make if the inductance is completely
swamped by the capacitance? Shirley, you jest.

The advantage to using pulses is that they are 'broadband' - they
don't have "A" frequency. The inductance and capacitance of the
system are unaffected by the small signals one impresses upon it.

What's different about the 'situ' during steady state that causes
electromagnetic fields to propagate differently than at other times?


They don't propagate differently but how does one separate
the forward wave from the reflected wave on a standing-wave
antenna? If you can do that, you will have solved the
measurement problem.

The antenna behaves physically in exactly the same way whether or not
it happens to be 'occupied' by waves, standing, sitting, or whatever
during measurement. If you want to know how long it take an
electromagnetic wave to traverse a conductor in any shape or
configuration, you pulse it and measure how long it takes, either to
get from one end to the other, or to be reflected back from the other
end. There are of course dispersion effects, and by studying the
change in the waveshape it is possible to deconvolve the frequency
dependent components. This is a matter of routine for practicioners.

73, ac6xg

Jim Kelley wrote:
The advantage to using pulses is that they are 'broadband' - they don't
have "A" frequency. The inductance and capacitance of the system are
unaffected by the small signals one impresses upon it.

But we are not interested in the phase delay for all
those other frequencies. We are only interested in the
phase delay at one particular frequency. And since we are
talking about distributed networks and not lumped circuits,
the inductance and capacitance of the coil does change with
frequency. Whatever measurements we make need to be made
at the frequency of operation.

The antenna behaves physically in exactly the same way whether or not it
happens to be 'occupied' by waves, standing, sitting, or whatever during
measurement. If you want to know how long it take an electromagnetic
wave to traverse a conductor in any shape or configuration, you pulse it
and measure how long it takes, either to get from one end to the other,
or to be reflected back from the other end.

If the pulse is not at the frequency of operation, the results
are hardly useful at all since the response of the loading coil
is frequency dependent.

So we are back to the original question. How can the delay through
a mobile loading coil be measured at the frequency of operation
in a standing-wave antenna?
--
73, Cecil, w5dxp.com

Cecil Moore wrote:

If the pulse is not at the frequency of operation, the results
are hardly useful at all since the response of the loading coil
is frequency dependent.

So we are back to the original question.

It's clear that you are still back at that question. That doesn't
necessarily apply to everyone else though. What I would suggest is
that you go back, re-read, and try to undertstand the post, in
particular the parts you deleted.

73, ac6xg

Jim Kelley wrote:
It's clear that you are still back at that question. That doesn't
necessarily apply to everyone else though. What I would suggest is that
you go back, re-read, and try to undertstand the post, in particular the
parts you deleted.

What's to understand? If the measurements are not made
at the operating frequency, there is no way to prove
that they are valid.

Both the velocity factor and the characteristic
impedance of a loading coil change dramatically
with frequency.

What is wrong with using a sinusoidal traveling
wave to measure the phase shift through a coil
at its frequency of operation?
--
73, Cecil, w5dxp.com

Cecil Moore wrote:
Jim Kelley wrote:

It's clear that you are still back at that question. That doesn't
necessarily apply to everyone else though. What I would suggest is
that you go back, re-read, and try to undertstand the post, in
particular the parts you deleted.


What's to understand? If the measurements are not made
at the operating frequency, there is no way to prove
that they are valid.

It appears that you would benefit from an understanding of the
spectral nature of broadband pulses.

Both the velocity factor and the characteristic
impedance of a loading coil change dramatically
with frequency.

What is wrong with using a sinusoidal traveling
wave to measure the phase shift through a coil
at its frequency of operation?

You need to be able to demonstrate that attaching a load resistor to a
standing wave antenna in order to turn it into a traveling wave
antenna does not dramatically change the characteristics.

73, Jim AC6XG