Current through coils
 

K7ITM wrote:
In fact, you don't even need to find the minimum and the maximum
points. Again, given sinusoidal excitation and a uniform line, some
small set of points with accurate amplitude measurement at each will
suffice, since they will uniquely determine the amplitudes of the two
waves and the line attenuation. You would have to know the spacing of
the points and that they were dense enough that there is not a spacial
aliasing problem (points distributed over more than 1/4 wavelength...).

Which points out, once again, that the phase information in a
standing wave is contained in the amplitude, not in the phase.
W7EL measured the *phase* of the standing-wave current which
is known not to contain any information as it is close to
unchanging all along a 1/2WL dipole or 1/4WL monopole. Yet he
reported it as meaningful. So far, nobody has made meaningful
phase shift measurements through a loading coil.

It's common to think of a standing wave as the result of two travelling
waves, one in each direction, but another way to think of a standing
wave pattern is as a pure standing wave plus a pure travelling wave.

One cannot get away from the fact that the pure standing wave
is the superposition of equal amplitude traveling waves flowing
in opposite directions. Some part of the forward traveling wave
must be allocated to the standing wave function. That part of
the traveling wave transfers no energy.

|Ifor| - |Iref| = |Ifor'| the part of the forward traveling wave
that is transferring energy.

|Ifor| - |Ifor'| = |Ifor''| = |Iref| the part of the forward
traveling wave that is contributing to the pure standing wave
and transferring no energy.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Cecil Moore wrote:
wrote:

I'll have to think about that a while and how it might affect what I am
saying.
(snip)
So here's the EZNEC example and an experiment that any
properly equipped person can duplicate. That includes
you and W7EL.

I took W7EL's EZNEC file and changed wire #203 from 0.25'
to 31.25'. At the 'tip' of the antenna, I installed a
439.2 ohm load that turns the antenna into a 90 degree
long *traveling-wave* antenna. Note that the current
magnitude at the top of the coil is identical to the
current magnitude through the load resistor. The load
resistor's value is very close to the calculated Z0
of the 31' #16 wire two feet above ground, using the
formula for a single wire transmission line above
ground.

The graphic is at http://www.qsl.net/w5dxp/test316y.GIF

The EZNEC file can be downloaded from:

http://www qsl.net/w5dxp/test316y.EZ
(snip)

Excellent!

Can you use this example, with varying frequency to explore your
assertion that the time delay (frequency times phase shift) of the
coil varies little over a significant range of frequencies up to self
resonance, and that that delay is about 1/4 cycle of the self resonant
frequency?

A graph of delay versus frequency would be useful. It should show
over what frequency range the coil acts mostly like a transmission
line and where it acts mostly like something else (i.e. inductor,
parallel resonant tank).

Current through coils
 

EVERYTHING????

I thought there is/was a restriction that "Everything" must include "a
significant portion of a wavelength".

:-)

Reg Edwards wrote:

EVERYTHING has Inductance, Capacitance and Resistance, and therefore
behaves as a transmission line.
----
Reg, G4FGQ

Current through coils
 

John Popelish wrote:
Can you use this example, with varying frequency to explore your
assertion that the time delay (frequency times phase shift) of the coil
varies little over a significant range of frequencies up to self
resonance, and that that delay is about 1/4 cycle of the self resonant
frequency?

I will do that when my energy level returns after getting
home at 2 am this morning. Note that anyone can download
the EZNEC file from http://www.qsl.net/w5dxp/test316y.EZ

A graph of delay versus frequency would be useful. It should show over
what frequency range the coil acts mostly like a transmission line and
where it acts mostly like something else (i.e. inductor, parallel
resonant tank).

This coil, operated below its self-resonant frequency, has
phase shift of 15.68 degrees or ~0.044 wavelength (delay of
7.4 nS). Dr. Corum says anything over 15 degrees requires
the distributed network model. 15 degrees will transform
50 ohms to 54+j120 ohms, causing SWR to be erroneously
reported as 7:1 instead of 1:1. That sounds like too
large an error to me.

Since the lumped-circuit model assumes a delay of zero, i.e.
faster than light, seems the use of the lumped-circuit model
results in 100% error, or infinite error if one calculates
it the other way. :-)

BTW, one of the principles on the other side of the argument
sent me a file with a worm in it. I guess he wanted to
extend the silence caused by my trip by bringing down my
computer.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Cecil Moore wrote:

This coil, operated below its self-resonant frequency, has
phase shift of 15.68 degrees or ~0.044 wavelength (delay of
7.4 nS). Dr. Corum says anything over 15 degrees requires
the distributed network model. 15 degrees will transform
50 ohms to 54+j120 ohms, causing SWR to be erroneously
reported as 7:1 instead of 1:1. That sounds like too
large an error to me.

Since the lumped-circuit model assumes a delay of zero, i.e.
faster than light, seems the use of the lumped-circuit model
results in 100% error, or infinite error if one calculates
it the other way. :-)

Not if the lumped inductor model includes lumps of capacitance that
represent the strays to ground. Lumped LC networks exhibit phase
shift, also.

BTW, one of the principles on the other side of the argument
sent me a file with a worm in it. I guess he wanted to
extend the silence caused by my trip by bringing down my
computer.

Never blame malice when ignorance will suffice. Even if you are
wrong, you will sleep better.

Current through coils
 

On Sun, 26 Mar 2006 15:12:23 GMT, Cecil Moore
wrote:
Don't you find it strange that all the wire in the
system occupies 90.01 - 15.68 = 74.33 degrees?

Strange?

1. The current distribution shown on the web is different than
the current distribution shown in the model;
2. -4.91 + -20.59 + -90.01 = -115.51 is different than
90.01 - 15.68 = 74.33
3. The coil Vf shown on the web is 0.1375 is different than
eq (32) = 0.0078
4. refuting your own references (Corum²).

not strange at all.

Current through coils
 

John Popelish wrote:
Can you use this example, with varying frequency to explore your
assertion that the time delay (frequency times phase shift) of the coil
varies little over a significant range of frequencies up to self
resonance, and that that delay is about 1/4 cycle of the self resonant
frequency?

Please don't put words in my mouth. What I have previously said
is that the delay can be *ROUGHLY* calculated using the self-
resonant frequency. I said something about +/- 50% accuracy.
Here's what EZNEC reports as the phase shift through the coil
in the traveling wave antenna previously tested at 5.89 MHz.

5.5 MHz: 14.1 deg, 5.89 MHz: 15.7 deg, 6 MHz: 16.2 deg,
7 MHz: 21.4 deg, 8 MHz: 29.5 deg, 9 MHz: 45.9 deg,
10 MHz: 89 deg, 11 MHz: 141.4 deg, 12 MHz: 163.0 deg,
13 MHz: 172.3 deg, 13.7 MHz: 183.82 deg.

The linear delay calculation is off by 59%, not too far from
my 50% rough estimate. Please note that the above values of
delays reported by EZNEC are nowhere near the 3 nS measured
by W8JI in the standing wave environment.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

On Sun, 26 Mar 2006 17:21:17 GMT, Cecil Moore
wrote:

I said something about +/- 50% accuracy.
The linear delay calculation is off by 59%, not too far from
my 50% rough estimate.

error is growing faster than the national debt. ;-)

nowhere near the 3 nS measured
by W8JI in the standing wave environment.

On Sun, 26 Mar 2006 16:39:57 GMT, Cecil Moore
wrote:
delay of 7.4 nS

Hmm, giving Tom the same grace of 59% reveals that the figures above,
7.4nS ±59% (4.4 - 11.77)
and
3nS ±59% (1.77 - 4.77)
overlap.

The thing about error (especially when it is in a growth mode
indicating loss of control over the experiment) is that you don't know
where within the band of possible values that the actual value
resides.

So, comparing the one to the other, making a claim that the other is
invalid, must necessarily invalidate both as they are convergent. Such
is the legacy of poor quality control.

It might be tempting to perform a Hail Mary save, by suddenly
declaring they are both right. :-)
but at 59% error, we can all agree that's a fantasy. Stretching your
tolerance for error to fit your argument can lead to any conclusion.

Current through coils
 

Richard Clark wrote:
1. The current distribution shown on the web is different than
the current distribution shown in the model;

Don't you know how to turn on the 'Current Phase' option when
displaying EZNEC results. Do you need a tutorial?

2. -4.91 + -20.59 + -90.01 = -115.51 is different than
90.01 - 15.68 = 74.33

The phase of the source is referenced at zero degrees. The
currents along the antenna are lagging the source current.
-4.91 deg is the phase of the current at the bottom of the
coil. -20.59 deg is the phase of the current at the top of
the coil. -90.01 deg is the phase of the current at the end
of the antenna. Trying to add those phases shows a lot of
ignorance.

3. The coil Vf shown on the web is 0.1375 is different than
eq (32) = 0.0078

Sorry, you're wrong. eq(32) for this coil yields a VF of ~0.033
which Dr. Corum claims to be accurate within about 10%. The
coil VF on the web is at 5.89 MHz, *NOT* at the self-resonant
frequency.

4. refuting your own references (Corum²).

Dr. Corum's equation for the coil VF is at its *SELF-RESONANT*
frequency, not anywhere else. Using it anywhere else is only
a *VERY ROUGH* estimate. At the self resonant frequency reported
by EZNEC, the VF calculates out to be ~0.055.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Richard Clark wrote:
On Sun, 26 Mar 2006 15:12:23 GMT, Cecil Moore
wrote:

Don't you find it strange that all the wire in the
system occupies 90.01 - 15.68 = 74.33 degrees?


Strange?

1. The current distribution shown on the web is different than
the current distribution shown in the model;
2. -4.91 + -20.59 + -90.01 = -115.51 is different than
90.01 - 15.68 = 74.33
3. The coil Vf shown on the web is 0.1375 is different than
eq (32) = 0.0078
4. refuting your own references (Corum²).

not strange at all.

Hi Richard,
Cecil never actually reads his references, he just
gives them and hopes you won't read them either. If he'd
bothered to look at figure 2 in the Corum reference he would
have found that the Corums had in mind a shorted stub as a
substitute for their Tesla coil. That's o.k., since it would lead
to an inductance (jZc*tan(Betag*h)) which they could use in the
time-honored way to resonate with the capacitance of the rest
of the circuit.
You're right, not strange at all.
73,
Tom Donaly, KA6RUH