Phase Shift through a 75m Texas Bugcatcher Coil
 

On Wed, 16 May 2007 08:43:03 -0500, (Richard
Harrison) wrote:

In other words, pick a point on a waveform. The rate at which it moves
is phase velocity. That`s the velocity of propagation.

Hi Richard,

The velocity of an imaginary point that contains no information nor
energy.

73's
Richard Clark, KB7QHC

Phase Shift through a 75m Texas Bugcatcher Coil
 

Richard Clark wrote:
'The velocity of a point that contains no information nor energy."

The topic of "phase shift" relates to alternating electrical current,
that is volts and amps. These are essential to energy and they are
represented by symbols which are manipulated to solve our problems. A
sinusoidal wave is the symbol of the periodic variation of electrical
properties with time. Volts and amps taken in-phase represent real
energy.

All points on a sinusoidal traveling wave move with the same velocity
past a fixed point. So, to determine the velocity of the motion, choice
of a particular point on the wave, be it zero or peak value, no matter
where the wave travels, or how attenuated, is always the zero or peak
value of the alternation. For velocity, choice of the particular point
to use is immaterial.

The symbol of the wave contains the information. The wave itself
contains the energy.

Best regards, Richard Harrison, KB5WZI

Phase Shift through a 75m Texas Bugcatcher Coil
 

Richard Clark wrote:
On Wed, 16 May 2007 08:43:03 -0500, (Richard
Harrison) wrote:


In other words, pick a point on a waveform. The rate at which it moves
is phase velocity. That`s the velocity of propagation.


Hi Richard,

The velocity of an imaginary point that contains no information nor
energy.

Why such criticism of a meager geometrical object with such useful
purpose? It seems your expectations may be too high.

ac6xg

Phase Shift through a 75m Texas Bugcatcher Coil
 

On Wed, 16 May 2007 10:57:58 -0500, (Richard
Harrison) wrote:

Richard Clark wrote:
'The velocity of a point that contains no information nor energy."

What I in fact said was:
The velocity of an imaginary point that contains no information nor
energy.
in response to:
In other words, pick a point on a waveform. The rate at which it moves
is phase velocity. That`s the velocity of propagation.

My response is still valid in science and technology. Richard, if you
choose to challenge this, cite an explicit reference that says Phase
Velocity contains information and energy. Further demonstrate how
your accrual of these characteristics on Phase Velocity does not then
change it to Group Velocity. It is Group Velocity that propagates
information and energy.

73's
Richard Clark, KB7QHC

Phase Shift through a 75m Texas Bugcatcher Coil
 

On Wed, 16 May 2007 09:37:17 -0700, Jim Kelley
wrote:

Why such criticism of a meager geometrical object with such useful
purpose? It seems your expectations may be too high.

Hi Jim,

MY expectations are too high? "With such useful purpose" is
overarching by half.

What has Phase Velocity got to do with anything, and what are its
expectations either high or low?

73's
Richard Clark, KB7QHC

Phase Shift through a 75m Texas Bugcatcher Coil
 

Richard Clark, KB7QHC wrote:
"The velocity of an imaginary point contains no information nor energy."

You could imagine a point like that. I regret omitting the word
"imaginary". It was unintentional.

I gave a dictionary definition of "phase velocity". It seems to be
synonymous with propagation velocity. The same dictionary defines group
velocity, and says:
"Group velocity differs from phase velocity in a medium in which the
phase velocity varies with frequency."

If phase variation with frequency is severe, and if the signal contains
multiple frequencies, I think it would likely alter the waveform.

Best regards, Richard Harrison, KB5WZI

Phase Shift through a 75m Texas Bugcatcher Coil
 

Richard Clark wrote:
On Wed, 16 May 2007 09:37:17 -0700, Jim Kelley
wrote:


Why such criticism of a meager geometrical object with such useful
purpose? It seems your expectations may be too high.


Hi Jim,

MY expectations are too high? "With such useful purpose" is
overarching by half.

Perception only. Utility in geometrical abstracts exists completely
independently of ones appreciation of them.

What has Phase Velocity got to do with anything, and what are its
expectations either high or low?

For the problem at hand (antennas) Kraus uses c = w/k, not dw/dk.
Naturally, he was interested in the velocity with which field lines
move across a point - the speed at which the wave propagates.
VF = v sub p over c, not v sub g over c. The second part of your
question is unintelligible to me.

ac6xg

Phase Shift through a 75m Texas Bugcatcher Coil
 

Richard Clark, KB7QHC wrote:
"Richard, if you choose to challenge this, cite an explicit reference
that says Phase Velocity contains information and energy."

I already have in two previous postings in this thread. One quotation
was from Terman and the other was from Lenkurt. Both explained how a
traveling wave tube (TWT) works. It uses velocity modulation of an
electron beam to alter the phase and power of a signal carried by a coil
encircling the electron beam. There`s your information and energy.

Best regards, Richard Harrison, KB5WZI

Phase Shift through a 75m Texas Bugcatcher Coil
 

Richard Harrison wrote:
I calculate about 628 inches of wire in the coil compared with about 10
inches of coil length. It is 62.8 times as far to go around the turns on
the coil as it is to travel through a 10 inch rod. So, velocity factor
is the quotient of 10 divided by 628, or about 0.016. That agrees with
EZNEC.

I think we are talking about two different coils. The 6" dia,
6" long, 30 turn Texas Bugcatcher coil is the one with a
VF of 0.016 per EZNEC. The only 10" coil that I remember
being mentioned is w8ji's and EZNEC cannot model that coil.

Dr. Corum's equation yields a VF of 0.0328 for the w8ji coil,
again just about double what the "threaded bolt" approach
indicates.
--
73, Cecil http://www.w5dxp.com

Phase Shift through a 75m Texas Bugcatcher Coil
 

Richard Harrison wrote:
Richard Clark, KB7QHC wrote:
"The velocities of what?"

Figure 8-32 labels the ordinate values as "relative phase velocity".
Phase velocity is defined in my electronic dictionary as:
"The velocity at which a point of constant phase is propagated in a
progressive sinusoidal wave."

In other words, pick a point on a waveform. The rate at which it moves
is phase velocity. That`s the velocity of propagation.

What Kraus may be talking about is the apparent speeding
up of the signal compared to the "threaded bolt" calculation.
When 600 inches of wire is coiled into a helix, how can
EM waves travel through that 600 inches of wire faster than
it can travel through 600 inches in free space? Reckon that
is what he is talking about?
--
73, Cecil http://www.w5dxp.com