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

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 arguing with Kraus.

No doubt, your bolt comparison is valid when each turn on
the "coil" is one wavelength long. But what happens when
each turn is 0.006 wavelength? Do you reckon something
might change?

Hopefully, I am not disagreeing with Kraus. It appears that
the question is: Does Kraus' one wavelength per turn helical
antenna have the same VF as a 75m Texas Bugcatcher loading coil?

Kraus' own graph shows that if one varies the turn circumference,
the phase velocity is not a linear correspondence. I would suggest
that lack of linear correspondence occurs in the 75m Texas Bugcatcher
coil. We cannot tell what the exact phase difference would be at
0.006 wavelength per turn, but the trend seems obvious to me.
--
73, Cecil http://www.w5dxp.com

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

Jim Kelley wrote:
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.

My 3rd edition only shows coil circumferences between 0.6
and 1.5 wavelengths. But the relative phase velocity is
1.0 when the circumference is 1.1 wavelength and the pitch
angle is 5 degrees. If the relative phase velocity is 1.0
when the circumference is 1.1 WL, doesn't that imply a
change in VF away from a straight piece of wire?
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:

Jim Kelley wrote:

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.


My 3rd edition only shows coil circumferences between 0.6
and 1.5 wavelengths. But the relative phase velocity is
1.0 when the circumference is 1.1 wavelength and the pitch
angle is 5 degrees. If the relative phase velocity is 1.0
when the circumference is 1.1 WL, doesn't that imply a
change in VF away from a straight piece of wire?

Hi Cecil,

The entire point of Richard's citation is that VF is a function of
pitch to circumference ratio. It explains the very thing that you
need to support your argument about phase delay across a coil. It's
what I meant when I said "I still think it would be prudent to explore
and understand the precise nature of the delay through the coil more
thoroughly before making too many assumptions about this."

Beyond that, I don't understand the question. Kraus is pretty
explicit. I didn't see much need to read between the lines. But all
I have to look at is the scanned version on the web that someone
posted a link to a week or so ago.

You should send Richard H. a fruit basket. Who woulda thought to look
under Helical Antennas. :-)

73, Jim AC6XG

Jim Kelley wrote:
The entire point of Richard's citation is that VF is a function of pitch
to circumference ratio. It explains the very thing that you need to
support your argument about phase delay across a coil.

Does "circumference" mean the circumference of the coil or
is it the actual wire length once around the helix?
--
73, Cecil http://www.w5dxp.com

On May 9, 4:28 pm, Cecil Moore wrote:
Jim Kelley wrote:
The entire point of Richard's citation is that VF is a function of pitch
to circumference ratio. It explains the very thing that you need to
support your argument about phase delay across a coil.

Does "circumference" mean the circumference of the coil or
is it the actual wire length once around the helix?
--
73, Cecil http://www.w5dxp.com

2*Pi*radius

ac6xg

Jim Kelley wrote:
2*Pi*radius

Sorry, I'm a little handicapped since I have never seen
"Figure 7-19" and it has been removed from the web site.
--
73, Cecil http://www.w5dxp.com

Jim Kelley wrote:
But all I
have to look at is the scanned version on the web that someone posted a
link to a week or so ago.

Unfortunately, it has been removed. Did you save it?
--
73, Cecil http://www.w5dxp.com

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