This is a request to any readers of r.r.a.a who are
capable of performing the experiment that I performed.

Use the EXCEL file at:

http://www.w5dxp.com/CoilZ0VF.xls

to estimate the Z0 of your test coil. If the test entry
is greater than 1.0, try another coil.

Here is the test setup using a 75m Texas Bugcatcher coil:

http://www.w5dxp.com/coiltest.gif

Using a 50 ohm source, install an autotransformer to
achieve the Z0 of the test coil on its output.

Load the test coil with a non-inductive resistance
equal to its Z0 value.

This will ensure that most of the current flowing
through the coil is traveling-wave current and not
standing-wave current.

Report the phase shift through the test coil.

This is an easy test to do. Of course, none of the
resident gurus will run the test or report the results
if they do run the test because it will prove their
old wives' tale to be wrong.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:

Cecil:

You might find this link interesting:

http://www.amanogawa.com/

And especially this sub-URL:

http://www.amanogawa.com/archive/Dou...bleStub-2.html

Interactive smith charts ... screen shots of these should be a breeze.

Regards,
JS

On Dec 7, 5:09 pm, Cecil Moore wrote:
This is a request to any readers of r.r.a.a who are
capable of performing the experiment that I performed.

Use the EXCEL file at:

http://www.w5dxp.com/CoilZ0VF.xls

to estimate the Z0 of your test coil. If the test entry
is greater than 1.0, try another coil.

Here is the test setup using a 75m Texas Bugcatcher coil:

http://www.w5dxp.com/coiltest.gif

Using a 50 ohm source, install an autotransformer to
achieve the Z0 of the test coil on its output.

Load the test coil with a non-inductive resistance
equal to its Z0 value.

This will ensure that most of the current flowing
through the coil is traveling-wave current and not
standing-wave current.

Report the phase shift through the test coil.

This is an easy test to do. Of course, none of the
resident gurus will run the test or report the results
if they do run the test because it will prove their
old wives' tale to be wrong.

This experiment presents some challenges, particularly
the need for current probes, but I have some questions
on the physical arrangement of test circuit.

You appear to think of the coil as a section of transmission
line, having assigned it a Z0 of 4kohm. But a transmission
line has two terminals at each end. I only find one at each
end here. How is it that this exhibits transmission line
behaviour?

The auto transformer would appear to be unnecessary
since any reflections at the source end will simply add
to the forward signal which will appear at the output
and therefore compensate perfectly when comparing
the input and the output. Proper termination of the
output is necessary because reflections there may
alter the measurements. Leaving out the transformer
would simplify the experient. Do we really need it?

The circuit layout seems to just have a wire from
the bottom of the resistor back to the source. This is
only appropriate if you are assuming that all
components can be treated as lumped (and the
wire ignored) at the frequencies and component
size of interest. But I thought your main argument
was that these components were sufficiently large
that they could not be treated as lumped. If this
is the case, then the routing of the return wire
will have significant effects on the result. How
did you route this wire?

If the coil can be treated as a transmission line,
then the delay can be measured by simply sampling
the voltage at the input and the output. This will
be a much easier experiment than measuring the
current. Should I expect the same results if
I measure the voltage?

....Keith

Keith Dysart wrote:
How is it that this exhibits transmission line behaviour?

The equation for a single-wire transmission line over
ground is well known to be Z0 = 138*log(4D/d)

As a data point, take a look at:

http://www.w5dxp.com/coil512.ez

Here is the current for each turn as reported by EZNEC.

Load 1 Current = 1.02 A. at -3.15 deg.
Load 2 Current = 1.121 A. at -11.28 deg.
Load 3 Current = 1.211 A. at -17.09 deg.
Load 4 Current = 1.289 A. at -21.59 deg.
Load 5 Current = 1.352 A. at -25.22 deg.
Load 6 Current = 1.401 A. at -28.29 deg.
Load 7 Current = 1.436 A. at -31.0 deg.
Load 8 Current = 1.459 A. at -33.5 deg.
Load 9 Current = 1.47 A. at -35.89 deg.
Load 10 Current = 1.468 A. at -38.25 deg.
Load 11 Current = 1.454 A. at -40.66 deg.
Load 12 Current = 1.427 A. at -43.21 deg.
Load 13 Current = 1.387 A. at -46.04 deg.
Load 14 Current = 1.332 A. at -49.34 deg.
Load 15 Current = 1.261 A. at -53.5 deg.
Load 16 Current = 1.17 A. at -59.25 deg.
Load 17 Current = 1.057 A. at -68.49 deg.
Load 18 Current = 1.039 A. at -71.74 deg.

The auto transformer would appear to be unnecessary
... Do we really need it?

I don't know the answer to that question. I didn't
want any reflections from the coil.

How did you route this wire?

I used an aluminum ground plane for that "wire".
Since the wire is very short at 4 MHz, I assumed
not much transmission line effects in the wire.

Should I expect the same results if
I measure the voltage?

I doubt it. But the subject was the current through
a loading coil, not the voltage.
--
73, Cecil http://www.w5dxp.com

On Dec 9, 1:24 am, Cecil Moore wrote:
Keith Dysart wrote:
How is it that this exhibits transmission line behaviour?

The equation for a single-wire transmission line over
ground is well known to be Z0 = 138*log(4D/d)

Ahh. So the coil and the ground plane make the transmission
line, and the two terminals are between the coil and the
ground plane.

But I did not see D or d in the spreadsheet which computed
Z0.

How did you route this wire?

I used an aluminum ground plane for that "wire".
Since the wire is very short at 4 MHz, I assumed
not much transmission line effects in the wire.

I'd expect that repeatability will require the same
orientation of the coil with respect to the ground
plane. And the same height.

Of course this horizontal coil has a completely
different relationship to the ground than it would
when installed vertically in an antenna? Will the
results of the measurement be at all
applicable?

....Keith

Keith Dysart wrote:
On Dec 9, 1:24 am, Cecil Moore wrote:
Keith Dysart wrote:
How is it that this exhibits transmission line behaviour?
The equation for a single-wire transmission line over
ground is well known to be Z0 = 138*log(4D/d)

Ahh. So the coil and the ground plane make the transmission
line, and the two terminals are between the coil and the
ground plane.

Yes, it is an unbalanced transmission line.

Keith, I want to commend you on having an open-mind and
an ability to listen to what I am saying. That is the
best way to get down to the technical facts. Others on
this newsgroup are closed-minded with an inability to
listen presumably because they already know all there
is to know.

But I did not see D or d in the spreadsheet which computed
Z0.

Those must be secondary effects or else Dr. Corum would
have included them. Of course, Corum's coils are operated
against a very large ground plane. Corums's equation (50)
and (51) for Z0 are only concerned with the diameter of
the coil and the wavelength. However, the diameter of the
coil is roughly equivalent to the diameter of the wire
in a straight-wire configuration.

I'd expect that repeatability will require the same
orientation of the coil with respect to the ground
plane. And the same height.

Absolute repeatability is not necessary for conceptual
technical truths to emerge.

Of course this horizontal coil has a completely
different relationship to the ground than it would
when installed vertically in an antenna? Will the
results of the measurement be at all applicable?

If the range of results is 15ns to 35 ns, that will
be a clue that 3 ns is impossible. The absolute results
are not important. The spread of measurement values
will be enough to prove that 3 ns is outside of any
3 sigma limit.
--
73, Cecil http://www.w5dxp.com