Phase Shift through a 75m Texas Bugcatcher Coil
 

Jim Kelley wrote:
The only kind of electromagnetic waves I know about are the traveling
kind. Sorry I can't be more help.

Seems to beg the question - are standing-waves electromagnetic
waves? If so, why are they standing? If not, what are they?
(Rhetorical questions AFAIAC)
--
73, Cecil http://www.w5dxp.com

Phase Shift through a 75m Texas Bugcatcher Coil
 

Cecil Moore wrote:
Jim Kelley wrote:
Richard Harrison wrote:
"Since the velocity with which the signal propagates along the
helix wire approximates the velocity of light if the frequency is not
too low (caveat is unimportant, see footnote in book), the axial field
due to the signal advances with a velocity that is very closely the
velocity of light multiplied by the ratio of helix pitch to helix
circumference."

Fig. 7-19 is certainly interesting.

Cecil owes you a fruit basket I think. ;-)

Unfortunately, I must disagree (very slightly) with Kraus.
Using Kraus' concepts *verbatim*, the delay through a coil
would be the same whether the wire is coiled up or straightened
out (if I understand correctly what he is saying).

On my web page at w5dxp.com/current2.htm I have a 30 turn
coil with a diameter of 6" causing a 38 degree phase shift
at 3.8 MHz. If the coil were straightened out, it would be
about pi*6"*30 = 565 inches or 47 feet. Since a wavelength
is about 259 feet at that frequency, 47 feet would be about
65 degrees. So Kraus' rule-of-thumb is off by about 70%.
His VF would be about 0.009 where the actual VF is more
like 0.106. 65 degrees of wire doesn't replace 65 degrees
of antenna. In this case, 65 degrees of wire replaces
38 degrees of antenna. The "missing degrees" are in the
impedance discontinuity between the coil and stinger.

There is an interaction between turns that increases the
VF of the coil so there is a very tiny grain of truth in
what Tom says. The interaction between turns increases the
coil VF from Kraus' 0.009 to the actual value of 0.016
but certainly not all the way to 1.0 as W8JI asserts.

Kraus may have been off by 70% but W8JI is off by 6000%
so it seems that Kraus was still a lot closer to the
technical truth that W8JI ever was.

Cecil,

I don't have the third edition of Kraus' antennas book, but I do have
the second edition. He does not make that simplified statement in the
second edition. He has equations and charts showing how the Vf changes
with the dimensions of the coil and the wavelength. He also references a
paper by Chu and Jackson that is now about 60 years old. In that paper,
the authors show that the Vf increases dramatically as the relative
wavelength becomes longer with respect to the coil dimensions.

73,
Gene
W4SZ

Phase Shift through a 75m Texas Bugcatcher Coil
 

Cecil Moore wrote:
Jim Kelley wrote:
Perhaps it should be noted that electromagnetic waves and photons
travel neither faster nor slower than the speed of light in their
medium of travel.

Obviously true for traveling waves. But how about the
"electromagnetic waves and photons" involved in standing
waves? Some folk here would have us believe that they are
not moving at all.


Cecil,

So do you actually believe that standing waves are completely static and
inert?

73,
Gene
W4SZ

Phase Shift through a 75m Texas Bugcatcher Coil
 

Jim Kelley wrote:
Tom hasn't posted a single word to this thread that I am aware of. The
point is if you don't like what he says, you should take it up with
him. Know what I mean?

What is your agenda in asserting that the contents of
Tom's web page concerning loading coils and his past
postings on the subject are off limits for this newsgroup?
--
73, Cecil http://www.w5dxp.com

Phase Shift through a 75m Texas Bugcatcher Coil
 

Cecil, W5DXP wrote:
"But how about the electromagnetic waves and photons involved with
standing waves?"

Terman has an answer. The standing wave is only a manifestation of
interference between two waves traveling in opposite directions, so on
page 870 of his 1955 opus Terman writes:

"The directional characteristic of a resonant (standing wave) system is
the vector sum of the directional patterns pointed in opposite
directions, as illustrated in Fig. 23-8."

In other words, the wave traveling in one direction produces its pattern
and the wave traveling in the other direction produces its pattern. The
sum of the patterns in both directions is the directional pattern for
the rod or wire. Standing waves have nothing to do with it but to stand
there and do nothing.

Best regards, Richard Harrison, KB5WZI

Phase Shift through a 75m Texas Bugcatcher Coil
 

Gene Fuller wrote:
I don't have the third edition of Kraus' antennas book, but I do have
the second edition. He does not make that simplified statement in the
second edition.

I have the 3rd edition, but I have not been able to find
the previous quotations. I certainly hope that I am not
disagreeing with Kraus. "Coils" or "Loading Coils" are
not even in the index.
--
73, Cecil http://www.w5dxp.com

Phase Shift through a 75m Texas Bugcatcher Coil
 

Gene Fuller wrote:
So do you actually believe that standing waves are completely static and
inert?

Of course not, Gene, but some on this newsgroup apparently
believe that. (Hint: I said it was a rhetorical question).

Why do some posters on this newsgroup go out of their way
to deny the photonic nature of the two traveling wave
components that are the cause of the standing wave?
--
73, Cecil http://www.w5dxp.com

Phase Shift through a 75m Texas Bugcatcher Coil
 

Cecil. W5DXP wrote:
"Unfortunately, I must disagree (very slightly) with Kraus."

I had invited readers to the helical antenna pages of Kraus to support
my wave advance comparison to the progress of a threaded bolt. I had
looked at page 229 in the 3rd edition with its Figs. 8-8 and 8-9 or at
similar figures in an earlier edition.

Upon looking agin, I still believe the figs. support my bolt comparison.
In any case, I`d study long and hard before sarguing with Kraus.

Best regards, Richard Harrison, KB5WZI

Phase Shift through a 75m Texas Bugcatcher Coil
 

Jim Kelley wrote:
"Fig. 7-19 is certainly interesting."

Jim`s cryptic statement sent me on a search.

Eureka! My 1950 version of Kraus has that Fig. 7-19 on page 193. It
shows propagarion velocities found by several researchers as a function
of helix circumference.

Phase velocity is the velocity at which a point of constant phase is
propagated in a progressive (traveling) sinusoidal wave.

Best regards, Richard Harrison, KB5WZI

Phase Shift through a 75m Texas Bugcatcher Coil
 

Richard Harrison wrote:

Cecil. W5DXP wrote:
"Unfortunately, I must disagree (very slightly) with Kraus."

I had invited readers to the helical antenna pages of Kraus to support
my wave advance comparison to the progress of a threaded bolt. I had
looked at page 229 in the 3rd edition with its Figs. 8-8 and 8-9 or at
similar figures in an earlier edition.

Upon looking agin, I still believe the figs. support my bolt comparison.
In any case, I`d study long and hard before sarguing with Kraus.

Best regards, Richard Harrison, KB5WZI


I didn't quite grasp the purpose of your bolt comparison, Richard.
The only limits Kraus puts on helices is that they are helical -
anything between a flat single turn loop at one limit and a straight
line at the other.

73, ac6xg