Jim Kelley wrote:
"I don`t quite grasp the purpose of your bolt comparison, Richard."

My point was that the signal is guided by the wire on the coil and isn`t
instantly transported by induction from one end of the coil to the
other. How long it takes the signal to travel the length of the coil
depends on the length of wire in the coil as well as the velocity factor
of the wave on the wire in the coil. If it were not so, Terman`s
explanation of the traveling wave tube (TWT) would not be valid. But,
GTE Lenkurt gives a similar explanation in its "Demodulator" of the TWT.
They manufactured TWT amplifiers and surely knew how they worked.

A coil is a coil whether it is used in a traveling wave tube or used to
load an antenna. The velocity factors are surely a function of coil
dimensions as illustrated by the research results given by Kraus in
Fig.7-19 in the 1950 edition of "Antennas". The variation surprises me.
There is probably more research which explains such variations.

Best regards, Richard Harrison, KB5WZI

On Wed, 9 May 2007 17:27:47 -0500, (Richard
Harrison) wrote:

A coil is a coil whether it is used in a traveling wave tube or used to
load an antenna.

Hi Richard,

That seems to be hardly so at the frequency under consideration, and
the application being described. TWTs and antenna loads vary
considerably with regard to this conjunction you are rhetorically
drawing.

A coil, in the classic circuit sense, is dimensionless in the face of
wavelength employed. (Yes, there are dimensions of length, radius,
and pitch etc.; yet and all, these are infinitesimal in comparison to
the wavelength of the signal analysis. If you move to the arena of
dimension becoming a significant portion of wavelength, then calling
it a coil is simply descriptive, not prescriptive. That is, it looks
like a coil, but it could in fact act like anything (such as
transmission line or antenna) or as a coil (but this would be a rare
occurrence). Hence, a coil is not always like a coil when there is
enough baggage such as the legacy of coil meaning inductance alone.

Many writers solve this by calling the structure a helix - which is
exactly the term used by Terman. So, a coil is a coil, except when it
is an helix.

The velocity factors are surely a function of coil
dimensions as illustrated by the research results given by Kraus in
Fig.7-19 in the 1950 edition of "Antennas". The variation surprises me.
There is probably more research which explains such variations.

I rely on his work in the same volume of 1955 that you have. The
velocity factors seem to be the same irrespective of sources or
terminology.

Returning to your first statement (taken last, here):
My point was that the signal is guided by the wire on the coil and isn`t
instantly transported by induction from one end of the coil to the
other.
The notion of instantaneous current and inductance is anathema.
However, phase lag via coupling should be a trivial computation and
the debate becomes one of degree (figuratively and literally). To
this point (and through the many years) few seemed interested in
quantification that would endanger the appearance of lofty discussion.

73's
Richard Clark, KB7QHC

On May 9, 3:27 pm, (Richard Harrison) wrote:
Jim Kelley wrote:

"I don`t quite grasp the purpose of your bolt comparison, Richard."

My point was that the signal is guided by the wire on the coil and isn`t
instantly transported by induction from one end of the coil to the
other. How long it takes the signal to travel the length of the coil
depends on the length of wire in the coil as well as the velocity factor
of the wave on the wire in the coil. If it were not so, Terman`s
explanation of the traveling wave tube (TWT) would not be valid. But,
GTE Lenkurt gives a similar explanation in its "Demodulator" of the TWT.
They manufactured TWT amplifiers and surely knew how they worked.

A coil is a coil whether it is used in a traveling wave tube or used to
load an antenna. The velocity factors are surely a function of coil
dimensions as illustrated by the research results given by Kraus in
Fig.7-19 in the 1950 edition of "Antennas". The variation surprises me.
There is probably more research which explains such variations.

Best regards, Richard Harrison, KB5WZI

Ok. But what I was asking is what does any of that have to do with a
bolt?

73, Jim AC6XG

On 9 May 2007 23:29:28 -0700, Jim Kelley wrote:

On May 9, 3:27 pm, (Richard Harrison) wrote:
Jim Kelley wrote:

"I don`t quite grasp the purpose of your bolt comparison, Richard."

My point was that the signal is guided by the wire on the coil and isn`t
instantly transported by induction from one end of the coil to the
other. How long it takes the signal to travel the length of the coil
depends on the length of wire in the coil as well as the velocity factor
of the wave on the wire in the coil. If it were not so, Terman`s
explanation of the traveling wave tube (TWT) would not be valid. But,
GTE Lenkurt gives a similar explanation in its "Demodulator" of the TWT.
They manufactured TWT amplifiers and surely knew how they worked.

A coil is a coil whether it is used in a traveling wave tube or used to
load an antenna. The velocity factors are surely a function of coil
dimensions as illustrated by the research results given by Kraus in
Fig.7-19 in the 1950 edition of "Antennas". The variation surprises me.
There is probably more research which explains such variations.

Best regards, Richard Harrison, KB5WZI

Ok. But what I was asking is what does any of that have to do with a
bolt?

The travel of one turn of a point at the radius (helical distance) in
relation to the travel of the same point in the depth (the linear
displacement after 360 degrees of the turn) is related to pitch. A
simple mechanical relationship. This is the bolt.

The signal flowing in the helix modulates a beam traveling within the
axis of the helix to impose its frequency upon it
(amplification/oscillation) through the pitch. This is the TWT.

The helical distance is supposed to express the linear completion of
the truncated 90 degrees of a quarterwave radiator. This is for the
loading coil.

There is no obvious correlation between the mechanical description,
the harmonic relation of the TWT and the degree relation of the
loading coil beyond the simple, visual metaphor which doesn't really
add any quid-pro-quo.

What is missing for the TWT is the necessary correlation of the beam
drift velocity which is wholly lacking from the bolt metaphor.

To say that the coil replaces the missing degrees of the truncated
quarterwave has likewise been so sloppily handled in the past, that
60-70% error brushed aside to prove equality provokes "so what?"

73's
Richard Clark, KB7QHC

Richard Clark wrote:
On 9 May 2007 23:29:28 -0700, Jim Kelley wrote:

Ok. But what I was asking is what does any of that have to do with a
bolt?


The travel of one turn of a point at the radius (helical distance) in
relation to the travel of the same point in the depth (the linear
displacement after 360 degrees of the turn) is related to pitch. A
simple mechanical relationship. This is the bolt.

Thanks so much, Richard. I'm going to keep this on file somewhere in
case I ever forget what a bolt is. :-)

73, ac6xg

On Thu, 10 May 2007 10:55:47 -0700, Jim Kelley
wrote:



Richard Clark wrote:
On 9 May 2007 23:29:28 -0700, Jim Kelley wrote:

Ok. But what I was asking is what does any of that have to do with a
bolt?


The travel of one turn of a point at the radius (helical distance) in
relation to the travel of the same point in the depth (the linear
displacement after 360 degrees of the turn) is related to pitch. A
simple mechanical relationship. This is the bolt.

Thanks so much, Richard. I'm going to keep this on file somewhere in
case I ever forget what a bolt is. :-)

Hi Jim,

So it's the only thing in this thread that makes sense....

73's
Richard Clark, KB7QHC