Gene, W4SZ wrote:
"What went wrong?"

Sorry, I can`t say because I haven`t followed this thread closely.

Surely the signal follows the path of the turns on a coil. Movement of
electrons is slothful but they are urged by the fields sweeping across
them.

Terman has but one mistake in his 1955 opus and it is only a
typographical error which is obvious, kilocycles instead of megacycles
or something of the sort and doesn`t affect understanding the subject.

Terman says on the "Mechanism of Operation of the Traveling-Wave Tube"
at the bottom of page 678:
"The applied signal propagates around the helix and produces an electric
field at the center of the helix that is directed along the helix axis.

That`s been read and re-read over 50 years and even repeated in the
"Lenkurt Demodulator". There is no chance it is wrong.

Best regards, Richard Harrison, KB5WZI

Richard Harrison wrote:

...
Terman says on the "Mechanism of Operation of the Traveling-Wave Tube"
at the bottom of page 678:
"The applied signal propagates around the helix and produces an electric
field at the center of the helix that is directed along the helix axis.
...
Best regards, Richard Harrison, KB5WZI


And, obeys basic rules, such as:

http://www.allaboutcircuits.com/vol_2/chpt_1/6.html

So, a summary of your point? Afraid I am a bit dense here today ...

Regards,
JS

John Smith wrote:
"So, a summary of your point?"

The velocity of the wave traveling on the turns of a coil is slightly
less than 300 million meters per second. Divide the number of meters of
wire in your coil by 300,000,000 and you get the number of seconds
required for the signal to get from one end to the other on the coil,
almost. Actual delay is slightly more because material surroundings slow
the wave a little more than a vacuum does. There is no magic
instantaneous transfer of energy from one turn to another within a coil.
If there were, Terman would have told us so.

Best regards, Richard Harrison, KB5WZI

Richard Harrison wrote:
... There is no magic
instantaneous transfer of energy from one turn to another within a coil.
If there were, Terman would have told us so.

Best regards, Richard Harrison, KB5WZI


Richard:

Thanks, got you now, and of course, no disagreement here. However, if
anyone has a view to the contrary, I would be interested in the
specifics ...

However, there is something akin "special case" which does come to my
mind: Say a two turn coils' configuration was changed to two single
turns ... somehow, even if insignificant, this same interaction of what
is occurring in one turns must be "felt" by the two turn coil. (crud, I
hope you can "decode" that ...)

What say you?

Regards,
JS

John Smith wrote:
However, if
anyone has a view to the contrary, I would be interested in the
specifics ...

In a coil wound on an iron-core toroid, do you believe
the flux follows the wire in the coil and ignores the
iron in the toroid?

Coupling is, of course, not nearly that good in an air-
core coil but coupling exists nonetheless. Some of
the current generated in a coil is through the air-core
transformer action between coils.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
John Smith wrote:
[said, "gray areas exist!]

In a coil wound on an iron-core toroid, do you believe
the flux follows the wire in the coil and ignores the
iron in the toroid?


At designed freqs, permeability of core material, turns
size/spacing--the core OVERWHELMS all other forms of magnetic
coupling--I cannot even begin to think how I would measure EM coupling
between turns in such an environment ...

Coupling is, of course, not nearly that good in an air-
core coil but coupling exists nonetheless. Some of
the current generated in a coil is through the air-core
transformer action between coils.

Air core, EM coupling between turns exists, in what degree--I simply
cannot, probably, afford the equipment to measure ...

As I stated, for at least the most part, we are in agreement ... it
seems only logical ... however, things are not always as they seem (now,
how's that for "wiggle room?" ;-) )

Regards,
JS

Richard Harrison wrote:
There is no magic
instantaneous transfer of energy from one turn to another within a coil.

It's not magic and it cannot occur at faster than light
speed. Magnetic coupling between air-core coils does
exist. It is just not of the magical magnitude asserted
by W8JI.

You wouldn't use the same argument on an iron-core
coil, would you, where virtually all of the coil#1
flux does indeed link with coil#N?
--
73, Cecil http://www.w5dxp.com

On Sat, 1 Dec 2007 16:59:43 -0600, (Richard
Harrison) wrote:

Terman says on the "Mechanism of Operation of the Traveling-Wave Tube"
at the bottom of page 678:
"The applied signal propagates around the helix and produces an electric
field at the center of the helix that is directed along the helix axis.

Hi Richard,

Do you want to comment on the sense of how a TWT helix in relation to
its wavelength of operation must impose a considerable operational
difference compared to a 2 inch diameter, 10 inch long coil at 80
Meters wavelength?

73's
Richard Clark, KB7QHC

Richard Harrison wrote:
Surely the signal follows the path of the turns on a coil.

Not entirely as adjacent turns do have an effect on
each other so there is a grain of truth in what W8JI
is saying. W8JI's error was in taking that grain of
truth and rationalizing that small grain into an
explanation that is off by at least a magnitude.

It looks like a reasonable rule of thumb is that the
velocity factor of a coil is approximately half what
it would be if the signal followed the wire entirely.
In other words, if one calculates the delay in the
length of wire used to wind the coil, the actual
delay through the coil is likely to be half of that
value.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
Richard Harrison wrote:
Surely the signal follows the path of the turns on a coil.

Not entirely as adjacent turns do have an effect on
each other so there is a grain of truth in what W8JI
is saying. W8JI's error was in taking that grain of
truth and rationalizing that small grain into an
explanation that is off by at least a magnitude.

It looks like a reasonable rule of thumb is that the
velocity factor of a coil is approximately half what
it would be if the signal followed the wire entirely.
In other words, if one calculates the delay in the
length of wire used to wind the coil, the actual
delay through the coil is likely to be half of that
value.

I follow you and am in some degree of agreement--now let toss there
stones at two of us ... LOL

This is most likely a gray area because of the lack of apparatus
available to most "normal" amateurs, which can do meaningful
measurements ...

Regards,
JS