Roy Lewallen wrote:
A single conductor doesn't have a characteristic impedance --

On the contrary, that is a false statement. In my
"Electronic Equations Handbook", it gives the
characteristic impedance for a single horizontal
wire about ground. Obviously, ground is the missing
conductor. I believe that equation is also given in
ARRL publications. A horizontal #14 wire 30 feet
above ground has a characteristic impedance very
close to 600 ohms. Since all of our antennas are
located a finite distance from ground, your assertion
seems ridiculous.

I actually built a vertical, loaded it with one, and made
careful measurements which I posted on this newsgroup several years ago.
Cecil is still complaining about it.

Yes, because the current on a standing wave antenna
doesn't change phase through the coil no matter what
the delay through the coil. EZNEC agrees with me.
Here is what EZNEC says about the current through
90 degrees of antenna:

EZNEC+ ver. 4.0
thin-wire 1/4WL vertical 4/21/2009 5:50:11 PM
--------------- CURRENT DATA ---------------
Frequency = 7.29 MHz
Wire No. 1:
Segment Conn Magnitude (A.) Phase (Deg.)
1 Ground 1 0.00
2 .97651 -0.42
3 .93005 -0.83
4 .86159 -1.19
5 .77258 -1.50
6 .66485 -1.78
7 .54059 -2.04
8 .40213 -2.28
9 .25161 -2.50
10 Open .08883 -2.71

How do you explain the fact that the current changes by
less than 3 degrees in 90 degrees of antenna? How can you
possibly measure the delay through a coil, or through a
wire, using a current like that?

The displacement current flowing through those capacitances, not some
"effective degrees of antenna" phenomenon, is what causes the current
along a solenoidal loading coil to vary.

Rhetorical question: Did you know that "displacement current"
is a patch added to the lumped circuit model to try to make
get closer to reality?

You've kind of lost me here, since I can't see how you've replaced a
two-terminal coil with a four-terminal transmission line. And a
transmission line doesn't radiate, so that sometimes-important property
of a solenoidal coil is ignored.

You wouldn't be lost if you knew that a single horizontal
wire above ground is a transmission line.

Me, too. The thing which prompted me to add the automated helix
generation feature to EZNEC was the realization that lumped loads so
often did a poor job of simulating solenoidal loading inductors.

Too bad you don't accept the EZNEC results of that addition
which I have posted on my web page and you have ignored.

P.S. Roy has threatened to refund my purchase price for EZNEC
and declare my copy of EZNEC to be a pirated copy unless I stop
using it to prove him wrong.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

Cecil Moore wrote:

Yes, because the current on a standing wave antenna
doesn't change phase through the coil no matter what
the delay through the coil. EZNEC agrees with me.
Here is what EZNEC says about the current through
90 degrees of antenna:

EZNEC+ ver. 4.0
thin-wire 1/4WL vertical 4/21/2009 5:50:11 PM
--------------- CURRENT DATA ---------------
Frequency = 7.29 MHz
Wire No. 1:
Segment Conn Magnitude (A.) Phase (Deg.)
1 Ground 1 0.00
2 .97651 -0.42
3 .93005 -0.83
4 .86159 -1.19
5 .77258 -1.50
6 .66485 -1.78
7 .54059 -2.04
8 .40213 -2.28
9 .25161 -2.50
10 Open .08883 -2.71

How do you explain the fact that the current changes by
less than 3 degrees in 90 degrees of antenna? How can you
possibly measure the delay through a coil, or through a
wire, using a current like that?

Not to intrude, but I thought you were discussing a coil. The above
seems to be about an antenna.

By extension, if an inductor acts the same as an antenna, then a
capacitor also acts like an antenna. QEF.

So I guess that implies that a capacitor isn't much different than an
inductor.

I've misunderstood so much, I think I may just have to end it all.

tom
K0TAR

Perhaps I could share a few thoughts on the "missing degrees" topic;
and again I apologise as the new boy if this has all been covered
before! I found the following argument helpful when trying to get my
head around some of the issues, and it may help others:

Picture the short, base-loaded, 6ft vertical antenna example I gave
earlier which resonates at 3.79MHz with the coil dimensions I quoted.
The 6ft whip represents an electrical length of about 9 degrees. Now
suppose I remove the 12" long loading coil leaving a 12" vertical gap
in the antenna. At this point I find it much more helpful to think in
terms of a "missing" +j2439 ohms reactance, rather than a "missing" 81
degrees, for reasons we shall see later.

Now I run out a couple of horizontal wires from where the top and
bottom of the coil were connected, and short them at the far end
thereby forming a short-circuit stub. That stub will insert some
"loading inductance" in place of the coil. How long do I need to make
the stub to bring the vertical back to resonance?

Using the simplified stub formula Xl=+jZo.tan(Bl), and assuming for
now that the characteristic impedance is 600 ohms, I find that the
electrical length needed to generate +j2439 is 76 degrees - well short
of any "missing" 81 degrees. And if I increase the characteristic
impedance of the stub to 1200 ohms I only need 64 degrees. The Corum &
Corum formulas tell me that the characteristic impedance of my
original loading coil is 2567 ohms at this frequency, so that only
requires an electrical length of 43 degrees.

So, for me, the "missing degrees" question is not really about missing
degrees; rather, it's about a missing inductive reactance which can be
provided by transmission line structures with a wide range of
electrical lengths depending on their characteristic impedance. The
"constant" is the reactance, not the electrical length.

I also find this picture helpful because I can visualize that,
although there must be forward and return waves on the stub, the net
current I would observe is a standing wave whose phase doesn't change
along the length of the stub. Incidentally, taking 43 degrees as the
length of my loading coil I would expect to see a change in current
amplitude along the length of the stub of cos(43); that's 0.73 -
pretty close to the 0.69 observed in the EZNEC model between the ends
of the coil.

Finally, I ask what the transmission line characteristic impedance
would need to be for its length to be exactly the "missing" 81
degrees? Answer: 2349/atan(81)=273 ohms. Isn't that in the right ball
park for the characteristic impedance of a single straight piece of
wire - in fact the piece of wire that's needed to turn the 6ft whip
into a full quarter-wave vertical?

And finally, finally, to Roy: I struggle with the "mental gymnastics"
needed to move from the simple stub model outlined above, to one where
the "transmission line" is a single wire, not two wires, and "in-line"
with the antenna elements. If you read the Curum & Corum paper I'm
sure it will be clearer to you than to me! But until I can understand
it better, I content myself with this thought: if we removed 56ft of
wire from our full-sized quarter-wave vertical to leave just the 6ft
whip, we'd be happy to analyse this 56ft straight piece of wire using
a transmission line approach (including considering forward &
reflected waves, and the resultant standing wave along it), and to
ascribe to it an equivalent inductive reactance. I don't understand
why I (we?) find it intellectually any more difficult to take the same
approach with a piece of wire once it is wound into a helix.

Regards,
Steve G3TXQ

steveeh131047 wrote:

Steve, congratulations on your QST article.

Now I run out a couple of horizontal wires from where the top and
bottom of the coil were connected, and short them at the far end
thereby forming a short-circuit stub. That stub will insert some
"loading inductance" in place of the coil. How long do I need to make
the stub to bring the vertical back to resonance?

I would also ask the questions: How much delay is there through
a series stub? What is the phase shift through the stub measured
by using the current on this standing-wave antenna? See below.

I also find this picture helpful because I can visualize that,
although there must be forward and return waves on the stub, the net
current I would observe is a standing wave whose phase doesn't change
along the length of the stub.

Someone is likely to point out that if one uses a current probe
to observe the current, it looks like a sine wave, i.e. its
phase is obviously changing with time. The point is that the
phase changes very little with length.

What we must be careful to say is that the phase doesn't change,
RELATIVE TO THE SOURCE PHASE, along the length of the stub. Here's
what EZNEC says about the phase in a 1/4WL open-circuit stub.

EZNEC+ ver. 4.0
1/4WL open stub in free space 4/22/2009 7:08:09 AM
--------------- CURRENT DATA ---------------
Wire No. 2:
Segment Conn Magnitude (A.) Phase (Deg.)
1 W1E1 .99665 -0.25
2 .97169 -0.67
3 .92292 -1.01
4 .85155 -1.30
5 .75929 -1.53
6 .64841 -1.72
7 .52163 -1.86
8 .38205 -1.96
9 .23309 -2.03
10 Open .07839 -2.07

Only 2 degrees of current phase shift in 90 degrees of stub.
How can that current be used to calculate delay through the
stub?
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

steveeh131047 wrote:
. . .
And finally, finally, to Roy: I struggle with the "mental gymnastics"
needed to move from the simple stub model outlined above, to one where
the "transmission line" is a single wire, not two wires, and "in-line"
with the antenna elements. If you read the Curum & Corum paper I'm
sure it will be clearer to you than to me! But until I can understand
it better, I content myself with this thought: if we removed 56ft of
wire from our full-sized quarter-wave vertical to leave just the 6ft
whip, we'd be happy to analyse this 56ft straight piece of wire using
a transmission line approach (including considering forward &
reflected waves, and the resultant standing wave along it), and to
ascribe to it an equivalent inductive reactance. I don't understand
why I (we?) find it intellectually any more difficult to take the same
approach with a piece of wire once it is wound into a helix.

Regards,
Steve G3TXQ

The similarities between an antenna and transmission line have been
known for a very long time and described in a number of papers. (See for
example Boyer, "The Antenna-Transmission Line Analog", _Ham Radio_,
April and May 1977, and Schelkunoff, "Theory of Antennas of Arbitrary
Size and Shape", _Proc. of the I.R.E., Sept. 1941.) It's a useful
conceptualization tool but, like comparing electricity to water in a
pipe, has its limitations. If you look at the transmission line
properties of a vertical, you see that the two conductors (the antenna
and ground plane) get farther and farther apart as the distance from the
feedpoint increases. This behaves like a transmission line whose
impedance increases with distance from the feedpoint and, in fact, a TDR
response shows just this characteristic. It's open circuited at the end,
so it behaves pretty much like an open circuited transmission line,
resulting in the same reflections and resulting standing waves you see
on a real antenna. One difficulty is accounting for the radiation, which
adds resistance to the feedpoint. I've never seen an attempt at
simulating it with distributed resistance, which I don't think would
work except over a narrow frequency range. Boyer deals with this by
simply adding a resistance at the model feedpoint, noting that the
resistance doesn't change very rapidly with frequency. So this is one
inherent shortcoming of the transmission line analog. As long as you
incorporate the increasing Z0 with distance from the feedpoint and the
limitations of the resistive part, the model does reasonably well in
predicting the feedpoint characteristics of simple antennas. But one
shortcoming of many antenna transmission line analogies is the attempt
to assign a single "average" or "effective" characteristic impedance to
the antenna, rather than the actual varying value. This is where a lot
of care has to be taken to assure that the model is valid in the regime
where it's being used.

There's no reason you can't also include a loading coil in the
transmission line model, and Boyer devotes much of the second part of
his article to doing just that. A solenoidal coil raises the
characteristic impedance of the length of "line" it occupies, because of
the increase in L/C ratio in that section. The traveling wave delay in
that section of the transmission line also increases due to the
increased LC product. (L and C are per unit length in both cases.) But
don't forget the C which is an essential part of this analysis, and
don't forget that the C is decreasing from the bottom to the top of the
coil, resulting in an increasing characteristic impedance. A very short
coil like a toroid will raise the Z0 only for a very short distance, so
behaves differently from a long solenoidal coil.

Models or analogs can be very useful in gaining insight about how things
work. You have to remain vigilant, though, that you don't extend the
analogy beyond it realm of validity.

Roy Lewallen, W7EL

Roy Lewallen wrote:
If you look at the transmission line
properties of a vertical, you see that the two conductors (the antenna
and ground plane) get farther and farther apart as the distance from the
feedpoint increases. This behaves like a transmission line whose
impedance increases with distance from the feedpoint and, in fact, a TDR
response shows just this characteristic.

So what? An ever increasing Z0 does not change the
basic characteristics of a standing wave antenna, one
characteristic of which is: The phase of the current
relative to the feedpoint current phase changes by
a minuscule amount. So exactly how did you use that
current to measure and calculate delay???

I've never seen an attempt at
simulating it with distributed resistance, ...

Then, just as I suspected, you have never looked at my
web pages. Radiation "loss" can easily be simulated by
resistance wire. Please download

http://www.w5dxp.com/stub_dip.EZ

and alleviate your ignorance.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

On Apr 22, 11:58*am, Cecil Moore wrote:
Roy Lewallen wrote:
If you look at the transmission line
properties of a vertical, you see that the two conductors (the antenna
and ground plane) get farther and farther apart as the distance from the
feedpoint increases. This behaves like a transmission line whose
impedance increases with distance from the feedpoint and, in fact, a TDR
response shows just this characteristic.

So what? An ever increasing Z0 does not change the
basic characteristics of a standing wave antenna, one
characteristic of which is: The phase of the current
relative to the feedpoint current phase changes by
a minuscule amount. So exactly how did you use that
current to measure and calculate delay???

I've never seen an attempt at
simulating it with distributed resistance, ...

Then, just as I suspected, you have never looked at my
web pages. Radiation "loss" can easily be simulated by
resistance wire. Please download

http://www.w5dxp.com/stub_dip.EZ

and alleviate your ignorance.
--
73, Cecil, IEEE, OOTC, *http://www.w5dxp.com

Anybody got a copy of the two articles that Roy alluded too
I would really like to read them
Regards
Art

Roy Lewallen wrote:
If you look at the transmission line
properties of a vertical, you see that the two conductors (the antenna
and ground plane) get farther and farther apart as the distance from the
feedpoint increases. This behaves like a transmission line whose
impedance increases with distance from the feedpoint and, in fact, a TDR
response shows just this characteristic. It's open circuited at the end,
so it behaves pretty much like an open circuited transmission line,
resulting in the same reflections and resulting standing waves you see
on a real antenna.

The Z0 characteristic impedance that matters is the
one that exists at the coil-stinger junction which
can be estimated from the single-wire transmission
line Z0 equation. It's usually in the neighborhood
of a few hundred ohms. For instance, a #14 horizontal
wire at 30 feet has a Z0 very close to 600 ohms
according to the formula.

One difficulty is accounting for the radiation, which
adds resistance to the feedpoint. I've never seen an attempt at
simulating it with distributed resistance, which I don't think would
work except over a narrow frequency range.

I have simulated such using EZNEC's wire resistivity
option. The resistance wire simulates the radiation
"loss" from the antenna. But for a standing wave
antenna, the "loss" to radiation is only about 20%
of the total energy stored on the standing wave
antenna. Therefore, a qualitative conceptual analysis
can be done assuming lossless conditions just as it
can be done with transmission lines.

But one
shortcoming of many antenna transmission line analogies is the attempt
to assign a single "average" or "effective" characteristic impedance to
the antenna, rather than the actual varying value. This is where a lot
of care has to be taken to assure that the model is valid in the regime
where it's being used.

Seems EZNEC automatically compensates for the varying Z0
so all we need to estimate is the single effective Z0 at
the coil to stinger impedance discontinuity.

There's no reason you can't also include a loading coil in the
transmission line model, and Boyer devotes much of the second part of
his article to doing just that. A solenoidal coil raises the
characteristic impedance of the length of "line" it occupies, because of
the increase in L/C ratio in that section. The traveling wave delay in
that section of the transmission line also increases due to the
increased LC product.

Are you saying the physics of the delay through a loading
coil changes between a traveling wave and a standing wave???
The standing wave is composed of a forward traveling wave
and a reflected traveling wave. They would experience the
same delay that you are talking about above.

So why didn't you use a traveling wave to measure the delay
through a loading coil??? Exactly how can the following
antenna current (from EZNEC) be used to calculate delay? The
current changes phase by 2.71 degrees in 90 degrees of
antenna. If the antenna was lossless, i.e. no radiation,
that current would not change phase at all.

EZNEC+ ver. 4.0
thin-wire 1/4WL vertical 4/23/2009 6:52:13 AM
--------------- CURRENT DATA ---------------
Frequency = 7.29 MHz
Wire No. 1:
Segment Conn Magnitude (A.) Phase (Deg.)
1 Ground 1 0.00
2 .97651 -0.42
3 .93005 -0.83
4 .86159 -1.19
5 .77258 -1.50
6 .66485 -1.78
7 .54059 -2.04
8 .40213 -2.28
9 .25161 -2.50
10 Open .08883 -2.71

--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

On Apr 23, 7:06*am, Cecil Moore wrote:
Roy Lewallen wrote:
If you look at the transmission line
properties of a vertical, you see that the two conductors (the antenna
and ground plane) get farther and farther apart as the distance from the
feedpoint increases. This behaves like a transmission line whose
impedance increases with distance from the feedpoint and, in fact, a TDR
response shows just this characteristic. It's open circuited at the end,
so it behaves pretty much like an open circuited transmission line,
resulting in the same reflections and resulting standing waves you see
on a real antenna.

The Z0 characteristic impedance that matters is the
one that exists at the coil-stinger junction which
can be estimated from the single-wire transmission
line Z0 equation. It's usually in the neighborhood
of a few hundred ohms. For instance, a #14 horizontal
wire at 30 feet has a Z0 very close to 600 ohms
according to the formula.

One difficulty is accounting for the radiation, which
adds resistance to the feedpoint. I've never seen an attempt at
simulating it with distributed resistance, which I don't think would
work except over a narrow frequency range.

I have simulated such using EZNEC's wire resistivity
option. The resistance wire simulates the radiation
"loss" from the antenna. But for a standing wave
antenna, the "loss" to radiation is only about 20%
of the total energy stored on the standing wave
antenna. Therefore, a qualitative conceptual analysis
can be done assuming lossless conditions just as it
can be done with transmission lines.

But one
shortcoming of many antenna transmission line analogies is the attempt
to assign a single "average" or "effective" characteristic impedance to
the antenna, rather than the actual varying value. This is where a lot
of care has to be taken to assure that the model is valid in the regime
where it's being used.

Seems EZNEC automatically compensates for the varying Z0
so all we need to estimate is the single effective Z0 at
the coil to stinger impedance discontinuity.

There's no reason you can't also include a loading coil in the
transmission line model, and Boyer devotes much of the second part of
his article to doing just that. A solenoidal coil raises the
characteristic impedance of the length of "line" it occupies, because of
the increase in L/C ratio in that section. The traveling wave delay in
that section of the transmission line also increases due to the
increased LC product.

Are you saying the physics of the delay through a loading
coil changes between a traveling wave and a standing wave???
The standing wave is composed of a forward traveling wave
and a reflected traveling wave. They would experience the
same delay that you are talking about above.

So why didn't you use a traveling wave to measure the delay
through a loading coil??? Exactly how can the following
antenna current (from EZNEC) be used to calculate delay? The
current changes phase by 2.71 degrees in 90 degrees of
antenna. If the antenna was lossless, i.e. no radiation,
that current would not change phase at all.

* * * * * * * * * * * *EZNEC+ ver. 4.0
thin-wire 1/4WL vertical * * 4/23/2009 * * 6:52:13 AM
* * * * * --------------- CURRENT DATA ---------------
Frequency = 7.29 MHz
Wire No. 1:
Segment *Conn * * *Magnitude (A.) *Phase (Deg.)
1 * * * *Ground * * 1 * * * * * * * *0.00
2 * * * * * * * * * .97651 * * * * *-0.42
3 * * * * * * * * * .93005 * * * * *-0.83
4 * * * * * * * * * .86159 * * * * *-1.19
5 * * * * * * * * * .77258 * * * * *-1.50
6 * * * * * * * * * .66485 * * * * *-1.78
7 * * * * * * * * * .54059 * * * * *-2.04
8 * * * * * * * * * .40213 * * * * *-2.28
9 * * * * * * * * * .25161 * * * * *-2.50
10 * * * Open * * * .08883 * * * * *-2.71

--
73, Cecil, IEEE, OOTC, *http://www.w5dxp.com

Cecil
The problem in this debate is that others are concentrating on
resonance
where as you are thinking in terms of anti resonance which portends to
a higher impedance and also the condition of equilibrium. When
considering the boundary law
one must recognise that momentum increases and decreases twice per
period. Thus when considering the boundary laws the negative area of
the sine wave must be placed underneath the positive area such that
momentum is taken account of.
When the diagram provided by Best on this thread was shown what it
described was the period was extended by the containment within the
boundary and where that containment extended the period which is now
longer than the period of non containment.In one case you have
accelleration and deaccelleration which is depicted
as the emmission of energy or flux. Consevation of energy laws demands
that for balance we must take into account the energy or flux that
enters the boundary to maintain equilibrium which is depicted by the
negative area of the sine wave period
such that this area is placed directly under the positive area while
still remaining within the arbritrary boundary. Thus we have
effectively changed the period when looking at a coil where the slow
wave is now half of the original wave as is theresonant point is half
of the anti resonant point which in terms of Newton and Maxwell
represents the point of equilibrium. When using the resonant point in
terms of relativity ie Maxwell you are seeing movement of a charge
from "a" to "b" which when repeated is repetitive movement in a single
direction. When using the anti resonant point the charge returns to
the starting point and if time is regarded as /dt
then the charge only moves in the vertical direction. Thus in terms of
Earth mass consists of energy movement in the ":z" plan and with
respect to the Universe the energy movement is solely in the "x" or
"y": direction until this action is equated with an action from the
opposite direction as per the law of Newton. Thus like Einstein
viewing the same action of Newton this thread is viewing the same
problem where one is static and one is relative but never the less the
same problem but relatively different. Pure physics my dear Watson
viewed fron different vantage points., one takes equilibrium into
account where as the other doesn't.
Not "babble"' David just an explanation per classical physics which is
the sole and only root of both mechanical and electrical engineering
Best regards
Art Unwin KB9MZ xg(uk)

Art Unwin wrote:
The problem in this debate is that others are concentrating on
resonance
where as you are thinking in terms of anti resonance which portends to
a higher impedance and also the condition of equilibrium.

I apologize if I gave you that idea, Art. I am talking
about a physically short (38 degrees), electrically 1/4WL
(90 degrees) *resonant* antenna over mininec ground. The
feedpoint impedance is low and resistive.

In the example given, the stinger supplies 19 degrees
of phase shift, the base-loading coil supplies 19 degrees
of phase shift, and the impedance discontinuity between
the coil and the stinger provides a point phase shift that
makes up the difference between 38 degrees and 90 degrees.

As I hammer away at this concept, I am wondering if a
loaded mobile antenna can be optimized if only the correct
model is adopted. Is a high-Q loading-coil always better
than a loading-coil with a lower Q? Are fat/short loading-
coils always better than skinny/long loading-coils? Some
field measurements have cast doubt on some long-held
concepts.

But obviously the question cannot be answered as long as
some people insist on using the lumped circuit model for
the loading coil, e.g. virtually zero delay through the
coil.

I have measured the delay through a 75m bugcatcher coil.
It was approximately 25 nS, a magnitude greater than
w8ji's "measurements". It doesn't matter if my measurements
were off by 20%. The magnitude difference between my
measurements and w8ji's "measurements" is too significant
to be ignored.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com