Loading Coils; was : Vincent antenna
 

Jim Kelley wrote:
In the face of such a redoubtable accusation I'm somewhat reluctant to
admit my view that a phase shift across a coil of this sort would in
fact be directly proportional to any propagation delay through that coil.

That's certainly true for traveling-wave current.
Definitely not true for standing-wave current which
doesn't change phase. I don't know that the comprehension
problem is here - maybe this graph will help.

http://www.w5dxp.com/travstnd.gif
--
73, Cecil http://www.w5dxp.com

Loading Coils; was : Vincent antenna
 

Tom Donaly wrote:
Gene Fuller wrote:
Cecil Moore wrote:

Take I = K1*cos(x)*cos(wt), a standing-wave equation.
Let t be any fixed value. cos(x) is an amplitude value
and does NOT vary with time. Therefore, the phase of the
standing-wave signal is constant at any particular time
and does NOT depend upon position along the wire or coil.

Now take I = K2*cos(x+wt), a traveling-wave equation.
Let t be any fixed value. The length dimension 'x'
has an effect on phase, i.e. the phase of of the
signal indeed does depend upon BOTH position AND time.


Cecil,

I know what you are trying to say, but you got the message screwed up.
If 't' is fixed, then the equations are essentially the same with
regard to 'x'. That is typical; a snapshot in time does not say much
about the wave behavior.

73,
Gene
W4SZ

It's generally cos(kx), but maybe Cecil is using a wave where k = 1,
that is, the wavelength is 2*Pi.
73,
Tom Donaly, KA6RUH

Tom,

Sure, that too.

I think one of the reasons this subject keeps coming back again, and not
only from Cecil, is that phase is deceptively simple and very easy to
misuse. A year or so ago I counted up at least 5 or 6 different meanings
of "phase" in routine use on RRAA. Lewis Carroll would feel right at
home here.

73,
Gene
W4SZ

Loading Coils; was : Vincent antenna
 

Richard Clark wrote:
Cecil Moore wrote:

I also measured ~12-13 ns delay
through 50 turns of the same coil stock that Tom
was using when he measured a 3 ns delay through
a 100 turn coil. That 12-13 ns delay is within
15% of the Corum equation predictions.

Using what equipment? And with what load?

Equipment was a dual-trace 100 MHz O'Scope. If I
remember correctly, the load was four 600 ohm non-
inductive resistors in series. My notes are in a
box somewhere.
--
73, Cecil http://www.w5dxp.com

Loading Coils; was : Vincent antenna
 

Tom Donaly wrote:
However, there is phase
information on a standing wave, and you know it.

Do you disagree with what Gene Fuller had to say?
The phase information is there all right but it is not in
the phase of the standing-wave - it is in the amplitude.
And W8JI did not use the amplitude to measure the phase.
Perhaps the following graph will help you to comprehend
this subject.

http://www.w5dxp.com/travstnd.gif
--
73, Cecil http://www.w5dxp.com

Loading Coils; was : Vincent antenna
 

Gene Fuller wrote:
Cecil Moore wrote:
Here's what Gene Fuller had to say about this subject:

There you go again; quoting a questionable source.

:-)
--
73, Cecil http://www.w5dxp.com

Loading Coils; was : Vincent antenna
 

Cecil Moore wrote:
Tom Donaly wrote:
However, there is phase
information on a standing wave, and you know it.

Do you disagree with what Gene Fuller had to say?
The phase information is there all right but it is not in
the phase of the standing-wave - it is in the amplitude.
And W8JI did not use the amplitude to measure the phase.
Perhaps the following graph will help you to comprehend
this subject.

http://www.w5dxp.com/travstnd.gif

Cecil,

That graph page is beyond simple amusement; it is hilarious.

73,
Gene
W4SZ

Loading Coils; was : Vincent antenna
 

Tom Donaly wrote:
It's generally cos(kx), but maybe Cecil is using a wave where k = 1,
that is, the wavelength is 2*Pi.

In the equations I posted, x is in degrees. It is (kx)
in the following graph:

http://www.w5dxp.com/travstnd.gif
--
73, Cecil http://www.w5dxp.com

Loading Coils; was : Vincent antenna
 

Gene Fuller wrote:
That graph page is beyond simple amusement; it is hilarious.

It was graphed from data generated by EZNEC and
agrees with what you said in an earlier posting,
that there is no phase information in the phase
of the standing-wave.
--
73, Cecil http://www.w5dxp.com

Loading Coils; was : Vincent antenna
 

On Tue, 04 Dec 2007 21:59:04 -0600, Cecil Moore
wrote:

Equipment was a dual-trace 100 MHz O'Scope. If I
What make, model?

Loading Coils; was : Vincent antenna
 

AI4QJ wrote:

Excellent information. The current along the coil reduces as it "replaces" a
section of an equivalent straight antenna section in degrees. This is true
even to the extent as existing current distribution in the section where the
coil is placed. I can see how someone in the 1950's might assume that
current in = current out (kirchoff) and not consider the degrees electrical
length occupied by the coil but ARRL should not be propagating such
information today. We know better now and besides, it is plain and simple
"intuitive" once you know that current changes along the electrical "degree
length" in an unloaded antenna, the same should happen in the degree length
loaded coil.

Thanks for taking the time to show the root of the controversy.

Also, as indicated, the pictures do say 1000 words and it also looks like
W8JI ended up agreeing with you after you pointed out the same effect at
"ON4UN's Low Band DXing", 3rd Edition, on page 9-34.

It's unfortunate that your intuition is wrong -- an inductor doesn't
"replace" part of an antenna.

If you'd like to learn a lot more about this, and the history of the
discussion, see my posting in this group on April 6, 2006 under the
topic " Current across the antenna loading coil - from scratch". It
includes some references to careful measurements I made more than a year
previous which showed that the simplified view of "replacement" is
flawed. If you have the stomach for it, look at the thread which
included the measurement postings, and see how well Cecil and Yuri were
able to do in applying their theory to predict the phase shift across a
simple, small toroidal inductor.

You can find archives of previous postings at http://groups.google.com.

Roy Lewallen, W7EL