Gene Fuller wrote:
I have stared at the W8JI web page
http://www.w8ji.com/inductor_current_time_delay.htm
for a long time, and I just cannot find anyplace where he mentions 4.5
degrees. Is that your calculation rather than Tom's?

Good Grief, Gene. Do you not know how to change ns of
delay to degrees of delay at 4 MHz? Assuming that some
posters may not know how, here's how.

Degrees of delay = 360(ns of Delay/WL/c)

The wavelength at 4 MHz is 246 feet. W8JI tells us that
the speed of light is 0.9821 ft/ns. That makes the delay
for a 3 ns delay equal to 4.47 degrees.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
Gene Fuller wrote:
I have stared at the W8JI web page
http://www.w8ji.com/inductor_current_time_delay.htm
for a long time, and I just cannot find anyplace where he mentions 4.5
degrees. Is that your calculation rather than Tom's?

Good Grief, Gene. Do you not know how to change ns of
delay to degrees of delay at 4 MHz? Assuming that some
posters may not know how, here's how.

Degrees of delay = 360(ns of Delay/WL/c)

The wavelength at 4 MHz is 246 feet. W8JI tells us that
the speed of light is 0.9821 ft/ns. That makes the delay
for a 3 ns delay equal to 4.47 degrees.

Cecil,

A proper "quote" does not include any extra analysis. If you want to add
your own explanation or disagreement, by all means do so. Incorrect
quoting simply destroys credibility for your argument.

W8JI did not say "4.5 degrees", you did.

(And yes, I do understand the equations.)

73,
Gene
W4SZ

Gene Fuller wrote:
Cecil Moore wrote:
Gene Fuller wrote:
I have stared at the W8JI web page
http://www.w8ji.com/inductor_current_time_delay.htm
for a long time, and I just cannot find anyplace where he mentions
4.5 degrees. Is that your calculation rather than Tom's?

Good Grief, Gene. Do you not know how to change ns of
delay to degrees of delay at 4 MHz? Assuming that some
posters may not know how, here's how.

Degrees of delay = 360(ns of Delay/WL/c)

The wavelength at 4 MHz is 246 feet. W8JI tells us that
the speed of light is 0.9821 ft/ns. That makes the delay
for a 3 ns delay equal to 4.47 degrees.

Cecil,

A proper "quote" does not include any extra analysis. If you want to add
your own explanation or disagreement, by all means do so. Incorrect
quoting simply destroys credibility for your argument.

W8JI did not say "4.5 degrees", you did.

(And yes, I do understand the equations.)

73,
Gene
W4SZ


I know one should not respond to his own post, but I want to follow up
with one more thing.

As far as I can tell, W8JI did not do any math or other type of analysis
to come up with the 3 ns delay. There was some surrounding discussion,
but the delay itself was simply read from an instrument.

So let me repeat my earlier questions.

What went wrong? Why is that number incorrect?

73,
Gene
W4SZ

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

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