Phase Shift through a 75m Texas Bugcatcher Coil
 

strange
if you dont know average andpeak net current and why use it?

On May 12, 4:33 pm, Cecil Moore wrote:
wrote:
i see nothing about average or peak net current there a t the link
i see no differences by value only of maytters of taste.

Don't worry, Don, many of the gurus on this newsgroup
don't comprehend it either. Maybe when the light dawns
upon them, they will explain it better than I can.
--
73, Cecil http://www.w5dxp.com

Phase Shift through a 75m Texas Bugcatcher Coil
 

Cecil, W5DXP wrote:
"The following web page is representative of the side that asserts there
is virtually zero delay through a 75m loading coil. But the backers of
that argument have grown strangely silent of late."

Coils generate counter-emf as a result of forward current and the
necessary magnetic field grows no faster than the current grows. Its
growth is delayed by the counter-emf.

Current does not jump off the rails in a coil. It follows the coil wire
as it follows a straight wire elsewhere. Terman says so and here is a
quotation from the "Lenkurt Demodulator of August 1965 which describes
the operation of a Traveling Wave Tube (TWT). Lenkurt used some of these
in heterodyne repeaters operating at 6 GHz because of their wide
bandwidth. Lenkurt`s description is very similar to Terman`s
description:
"The signal to be amplified by the tube is coupled into the gun end of
the helix. This RF signal travels as a surface wave around the turns of
the helix, toward the collector, at about the velocity of light. The
forward movement of the wave is analogous to the travel of a finely
threaded screw (I called it a bolt in my analogy) where many turns are
required to drive it into position. The signal wave generates an axial
electric field which travels*with it along the longitudinal axis of
the helix. This alternating electric field interacts or velocity
modulates the electrons in the beam."

The beam is pencil thin centered inside the helix. The beam is formed
and focused much like that inside a cathode ray tube. Its electrons are
accelerated by a high positive d-c voltage on the collector and
elsewhere in the tube. But that`s not all. Signal voltage on the helix
speeds and slows the beam at multiple points along the helix which is
many wavelengths long at 6 GHz. This advancement and retardation along
the length of the helix bunches up the electrons producing the velocity
modulation of the beam.

The helix is just a long spiral of wire inside the TWT. There are many
cycles of the 6 GHz signal distributed along the wave`s travel route.

Terman and Lenkurt say the signal route is along the wire in the coil. I
believe them.

Best regards, Richard Harrison, KB5WZI

Phase Shift through a 75m Texas Bugcatcher Coil
 

Richard Harrison wrote:
Cecil, W5DXP wrote:
"The following web page is representative of the side that asserts there
is virtually zero delay through a 75m loading coil. But the backers of
that argument have grown strangely silent of late."

Current does not jump off the rails in a coil.

Not disagreeing in general but just fine tuning a bit.
In an HF mobile loading coil, the EM waves are photonic
in nature so a few photons are capable of migrating to
adjacent turns - certainly not enough to cause the 3
nS delay through a 10 inch long 100 turn coil reported
by w8ji, but the effect is enough to roughly cut in half
the time taken for the current to negotiate the coil wire.

I have modeled a 75m Texas Bugcatcher coil at:

http://www.w5dxp.com/coil505u.EZ

The length of the wire used in that coil is ~48 feet.
A wavelength at 3.8 MHz is ~259 feet. So that 48 feet
equals about (360)(48/259) = ~67 degrees. Yet EZNEC
reports a phase shift of only ~38 degrees. The effect
of the interaction between adjacent coils increases the
velocity factor of the coil to roughly 1.8 times what it
would be if all the current were confined to the coil
wire. That's a VF increase from ~0.009 to ~0.016 but
certainly still magnitudes short of w8ji's reported
value of 0.988

The measured velocity factor as a function of the ratio
of coil-circumference/wavelength is presented by Kraus,
Figure 8-34 in the 3rd edition. Note that the phase
velocity is not a straight line function of circumference.

The velocity factor as a function of the ratio of
coil-diameter/wavelength has been plotted in Fig. 1
of: http://www.ttr.com/TELSIKS2001-MASTER-1.pdf
and is also not a straight-line function.
--
73, Cecil http://www.w5dxp.com

Phase Shift through a 75m Texas Bugcatcher Coil
 

Cecil, W5DXP wrote:
"The measured velocity factor as a function of the ratio of
coil-circumference/wavelength is presented by Kraus, Figure 8-34 in the
3rd edition."

Yes. The older edition, posted briefly on the web, has a Fig. 7-19 which
also has VF`s found by Chu & Jackson, and by Bagby. They also found
propagation faster than c for some coil circumferences / wavelength.
Photons, massless at rest, can do that.

Best regards, Richard Harrison, KB5WZI

Phase Shift through a 75m Texas Bugcatcher Coil
 

On Sun, 13 May 2007 07:23:15 -0500, (Richard
Harrison) wrote:

They also found
propagation faster than c for some coil circumferences / wavelength.
Photons, massless at rest, can do that.

Hi Richard,

This is beginning to descend into nonsense.

Forgive me, it has descended into nonsense long ago, what is happening
now is called porpoising (rising and falling deeper, repeatedly).

For instance the power in propagation cannot go faster than c for
anything - that is clearly absurd. Perhaps if you were to more deeply
cite your reference, then you would find what IS going faster in c has
no material content (this discussion is in the material being used by
you and I bet is the undisclosed topic of "group" velocity which is
thoroughly useless for 75M and subwavelength coils - again, there is a
world of difference between a coil and a helix in conventional
engineering usages).

Photons get a bad reputation here. There is no such thing as a
photon that is massless at rest - it is called an electron at a higher
energy level which definitely has mass (no doubt Cecil could Xerox an
obscure reference to prove it doesn't); OR it is rendered into a
massless Phonon, but Phonons by definition move (no such thing as rest
for them either); OR as a Plasmon, but Plasmons move too, but at a
different wavelength for the same frequency; OR as an Exciton....

The list of moving quasi-particles goes on, all of them moving. This
is something in distinct contrast to Cecil's threads that give only
the "appearance of motion."

73's
Richard Clark, KB7QHC

Phase Shift through a 75m Texas Bugcatcher Coil
 

Cecil Moore wrote:
...
Not disagreeing in general but just fine tuning a bit.
In an HF mobile loading coil, the EM waves are photonic
in nature so a few photons are capable of migrating to
adjacent turns - certainly not enough to cause the 3
nS delay through a 10 inch long 100 turn coil reported
by w8ji, but the effect is enough to roughly cut in half
the time taken for the current to negotiate the coil wire.
...

Cecil:

What would you offer as to the "photonic-jump", the capacitance of the
adjacent turns with air serving as the dielectric?


Since inductance lags and capacitance leads, wouldn't the inductance
value between turns serve to offset this? And, the diameter of the wire
become a major factor in the phenomenon you propose?

What if a spiral wound faraday shield is placed between the turns?
Would we still see this "photonic-jump?"

Regards,
JS

Phase Shift through a 75m Texas Bugcatcher Coil
 

John Smith I wrote:
What would you offer as to the "photonic-jump", the capacitance of the
adjacent turns with air serving as the dielectric?

When electrons are accelerated in a conductor, they
emit photons. Some photons are emitted from one turn
and migrate to the adjacent turn. One might think of
it as a few photons taking a shortcut. Another way
of saying the same thing is that the fields couple
turn-to-turn. The overall effect is to increase
the velocity factor of the coil by something like a
factor of two over the "threaded bolt" calculation.
However, the effect is still magnitudes too low to
explain the 100 turn, 3 nS coil delay described by
w8ji.

Standing wave current cannot be used to make valid
measurements about current amplitude "drops" across
or phase shifts through a loading coil. One must
instead figure out a way to get a traveling wave
flowing through the coil. Then the phase shift
becomes perfectly obvious.

I have taken Wes's helical coil from:

http://www.k6mhe.com/n7ws/Loaded%20antennas.htm

and modeled it with EZNEC. I then loaded the coil
with a 1250 ohm resistor to minimize reflected current
and took a look at the phase shift through the
coil. Turns out to be about 37 degrees at 7.15 MHz.
That makes it a delay of about 14.4 nS.

That coil512.EZ file can be downloaded from:

http://www.w5dxp.com/coil512.EZ
--
73, Cecil http://www.w5dxp.com

Phase Shift through a 75m Texas Bugcatcher Coil
 

On Sun, 13 May 2007 11:02:24 -0500, Cecil Moore
wrote:

Aside from 100% error (actually more) for Wes' coil,

I have taken Wes's helical coil from:
http://www.k6mhe.com/n7ws/Loaded%20antennas.htm
and modeled it with EZNEC. ...
That coil512.EZ file can be downloaded from:

is distinctly false.

Phase Shift through a 75m Texas Bugcatcher Coil
 

Richard Clark wrote:
On Sun, 13 May 2007 11:02:24 -0500, Cecil Moore
wrote:

Aside from 100% error (actually more) for Wes' coil,

I don't understand but will be glad to correct
any error.

I have taken Wes's helical coil from:
http://www.k6mhe.com/n7ws/Loaded%20antennas.htm
and modeled it with EZNEC. ...
That coil512.EZ file can be downloaded from:

is distinctly false.

In what way?
--
73, Cecil http://www.w5dxp.com

Phase Shift through a 75m Texas Bugcatcher Coil
 

On Sun, 13 May 2007 12:49:03 -0500, Cecil Moore
wrote:

In what way?

Abandon your Xerox ethic and actually read your reference. This
advice would work for other citations you copy off too.