inducors/form factors/radiation revisited
 

My last attempt on this subject only attracted lurkers and not those
that were technically minded so I thought I would try harder at the
communication side.
If one uses the present day modeling programs, items such as
inductance
are taken as point loads of zero length. Since in the real world
inductance does has length a way of modeling it would be to redraw it
as a distrubited
load along the length of the actual inductor. When doing this modeling
shows that current DOES NOT Change over the length of the inductance,
thus there is no radiation..
Ignoring intercapacitance this supports the previous stand of Tom and
Roy.
Taking this point further, one wonders why inductors in the real world
are not designed to be a point load, albiet in a two dimensional
world.
so that the length origionaly used by following published form factor
can be used to RADIATE . In this sense it follows that inductances
should be made in spiral form with special attention made to reducing
intercapacitance ala basket weave pancake design.
The above flies in the face of what is presently published in books
but so is the relationship of linear designs based on distance
between physical dipoles instead of the distance between current max
points so books are not infallable.
The above does also question the practice of grounding a center
point of a wound inductance since the above suggests that current is
NOT zero at that point! Since Roy was correct in the first place
maybe he will add some comments on what may be fallacious conclusions
that I made on my part.
Best regards
Art

Art Unwin KB9MZ wrote:
In this sense it follows that inductances
should be made in spiral form with special attention made to reducing
intercapacitance ala basket weave pancake design.

Art, I suspect a spiral pancake inductor would have
a low 'Q' and therefore high losses. Have you measured
the 'Q' of such an inductor?
--
73, Cecil, W5DXP

No I have not, but I have made one using hardline coax
for use on the antenna when the weather gets better.
we have ice up here !.
What is the basis of your suspicioun regarding 'Q' ?
Regards
Art

"Cecil Moore" wrote in message
...
Art Unwin KB9MZ wrote:
In this sense it follows that inductances
should be made in spiral form with special attention made to reducing
intercapacitance ala basket weave pancake design.

Art, I suspect a spiral pancake inductor would have
a low 'Q' and therefore high losses. Have you measured
the 'Q' of such an inductor?
--
73, Cecil, W5DXP

Art Unwin KB9MZ wrote:
No I have not, but I have made one using hardline coax
for use on the antenna when the weather gets better.
we have ice up here !.
What is the basis of your suspicioun regarding 'Q' ?

The flux from each loop flows across all the other
loops. A web search for "pancake coil" turns up some
interesting stuff including one company's claim that
their coil-on-chip process turns out coils with double
the 'Q' of pancake coils.

Incidentally, a pancake coil doesn't solve the magnitude
difference problem between current in and current out in
a standing wave antenna. It may not radiate but it certainly
has a delay through the coil which is what causes the current
in to be different from the current out in standing wave
antennas. This is explained on my web page at the bottom
of the page.
--
73, Cecil, http://www.qsl.net/w5dxp/current.htm


--
73, Cecil, W5DXP

Re "delay"
Puting a 'reactance' in series was done with an antenna
in that capacitors were inserted along the radiator..
Beaszely determined by using hiscomputor program that it did nothing to
enhance the antenna despite claims to the contrary. So yes, I agree there is
a phase change but that is where I stop
Regards
Art

"Cecil Moore" wrote in message
...
Art Unwin KB9MZ wrote:
No I have not, but I have made one using hardline coax
for use on the antenna when the weather gets better.
we have ice up here !.
What is the basis of your suspicioun regarding 'Q' ?

The flux from each loop flows across all the other
loops. A web search for "pancake coil" turns up some
interesting stuff including one company's claim that
their coil-on-chip process turns out coils with double
the 'Q' of pancake coils.

Incidentally, a pancake coil doesn't solve the magnitude
difference problem between current in and current out in
a standing wave antenna. It may not radiate but it certainly
has a delay through the coil which is what causes the current
in to be different from the current out in standing wave
antennas. This is explained on my web page at the bottom
of the page.
--
73, Cecil, http://www.qsl.net/w5dxp/current.htm


--
73, Cecil, W5DXP

The current out of one end of a coil of negligible length and diameter in
terms of a wavelength, for practical purposes is the same as the current
going into it - both magnitude and phase.


HOW ELSE CAN A TWO-TERMINAL DEVICE POSSIBLY BEHAVE?


And if by some impossibly remote chance you should discover something
different, so infringing all the known Laws of Physics and several more, of
what possible use could you make of it?


If you please, let's have the equations or forever hold your peace.


Of course, Cec, there never has been any chance of reforming your ideas on
the subject. But having just had a good swig of Vin de Pays D'OC, a
fortifying product of our sensible French friends 21 miles just across the
Channel, I mention it here only to protect, once and for all, professional
and amateur newcomers to the subject of coil-loaded anrennas from being led
unwittingly into the Mire of Despond and the Depths of Ignorance.


Cec, old friend, please forgive my slight tendency to exaggerate. ;o)


For newcomers wishing to appreciate the behaviour of coil-loaded vertical
antennas in a quantitative manner try down-loading in a few seconds program
LOADCOIL If you can't understand it no harm will be done.
----
.................................................. ..........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. ..........





--
.................................................. ..........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. ..........
"Cecil Moore" wrote in message
...
Art Unwin KB9MZ wrote:
No I have not, but I have made one using hardline coax
for use on the antenna when the weather gets better.
we have ice up here !.
What is the basis of your suspicioun regarding 'Q' ?

The flux from each loop flows across all the other
loops. A web search for "pancake coil" turns up some
interesting stuff including one company's claim that
their coil-on-chip process turns out coils with double
the 'Q' of pancake coils.

Incidentally, a pancake coil doesn't solve the magnitude
difference problem between current in and current out in
a standing wave antenna. It may not radiate but it certainly
has a delay through the coil which is what causes the current
in to be different from the current out in standing wave
antennas. This is explained on my web page at the bottom
of the page.
--
73, Cecil, http://www.qsl.net/w5dxp/current.htm


--
73, Cecil, W5DXP

Cecil Moore wrote in message ...
Art Unwin KB9MZ wrote:
No I have not, but I have made one using hardline coax
for use on the antenna when the weather gets better.
we have ice up here !.
What is the basis of your suspicioun regarding 'Q' ?

The flux from each loop flows across all the other
loops. A web search for "pancake coil" turns up some
interesting stuff including one company's claim that
their coil-on-chip process turns out coils with double
the 'Q' of pancake coils.

Cecil
I suspect that the 'Q' of a pancake coil would be higher than
the single layer solenoid coil.
!. Modeling shows that for a given length the inductance supplied
is about equal with the edge going to the pancake coil.
2 I believe it is well established that the'Q' of the standard coil
increases as the former radius increases.
Based on the above one could roughly equate the relative inductances
as somewhat proportional with the mean diameter of coils.
3 Since the first pancake coil would have a diaameter more than zero
I think one could say that the pancake coil would tend to have a
higher "Q'
and not the lower "Q" that you suspect.
If a whip coil was made pancake style would this not present less wind
resistance when going mobile ?
Cheers
Art





Incidentally, a pancake coil doesn't solve the magnitude
difference problem between current in and current out in
a standing wave antenna. It may not radiate but it certainly
has a delay through the coil which is what causes the current
in to be different from the current out in standing wave
antennas. This is explained on my web page at the bottom
of the page.
--
73, Cecil, http://www.qsl.net/w5dxp/current.htm

Reg Edwards wrote:
The current out of one end of a coil of negligible length and diameter in
terms of a wavelength, for practical purposes is the same as the current
going into it - both magnitude and phase.

HOW ELSE CAN A TWO-TERMINAL DEVICE POSSIBLY BEHAVE?

Real world loading coils are not of negligible length and diameter.
Kraus talks about phase-reversing coils. That means that current
is flowing into both ends of the coil at the same time. Please
take a look at the bottom of the web page below for an explanation.
--
73, Cecil http://www.qsl.net/w5dxp/current.htm



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"Art Unwin KB9MZ" wrote in message
m...
Cecil Moore wrote in message
...
Art Unwin KB9MZ wrote:
No I have not, but I have made one using hardline coax
for use on the antenna when the weather gets better.
we have ice up here !.
What is the basis of your suspicioun regarding 'Q' ?

The flux from each loop flows across all the other
loops. A web search for "pancake coil" turns up some
interesting stuff including one company's claim that
their coil-on-chip process turns out coils with double
the 'Q' of pancake coils.

Cecil
I suspect that the 'Q' of a pancake coil would be higher than
the single layer solenoid coil.
!. Modeling shows that for a given length the inductance supplied
is about equal with the edge going to the pancake coil.
2 I believe it is well established that the'Q' of the standard coil
increases as the former radius increases.
Based on the above one could roughly equate the relative inductances
as somewhat proportional with the mean diameter of coils.
3 Since the first pancake coil would have a diaameter more than zero
I think one could say that the pancake coil would tend to have a
higher "Q'
and not the lower "Q" that you suspect.

Cecil,
Correction needed here! The mean diameter of a pancake coil depends mainly
on the radius of the first coil form thus the "Q" can easily made of either
a higher "Q" or a lower "Q" over a standard solenoid style coil.depending on
the relative diameters'
Cheers
Art


If a whip coil was made pancake style would this not present less wind
resistance when going mobile ?
Cheers
Art





Incidentally, a pancake coil doesn't solve the magnitude
difference problem between current in and current out in
a standing wave antenna. It may not radiate but it certainly
has a delay through the coil which is what causes the current
in to be different from the current out in standing wave
antennas. This is explained on my web page at the bottom
of the page.
--
73, Cecil, http://www.qsl.net/w5dxp/current.htm

Art, KB9MZ wrote:
"Taking this point further, one wonders why inductors in the real world
are not designed to be a point load, albeit in a two dimensional world."

Seems we exhausted this topic some time ago. The ends of a coil do not
have to be 180-degrees out of phase due to the configuration and
composition of connections external to the coil. Waves traveling in
opposite directions through the coil can produce a standing wave within
the coil regardless of coil position. Energy into one end of a coil does
not necessarily equal energy out because radiation and conversion to
heat may not be uniform throughout the coil.

Nevertheless, I`m elated. I`ve found my copy of Terman`s "Electronic and
Radio Engineering".
On page 11, Terman says:
"Inductance in microhenrys = (F)(nsquared)(d)
n = number of turns
d = diameter of coil measured to center of wires
F = constant that depends only upon the ratio of length to diameter,
given in Fig 2.2"

The inductance formula above is for a single-layer solenoid. The
footnote says:
"A comprehensive collection of such formulas is given by F.E. Terman,
"Radio Engineers` Handbook" pp 48-64, McGraw-Hill Book Company, Inc.,
New York, 1943."

On pages 59 and 60 of Terman`s "Handbook" he treats a "Flat Retangular
Coil". He gives a formula (47) for its inductance, which is complicated
by multiple dimensions, length, width, etc. Inductance is nevertheless
proportional to the square of the number of turns as in the case of a
solenoid.

My Terman`s Handbook is difficult for me to read due to its damage in a
flood a few years ago. Its pages are stuck together and torn, but it`s
worth trying to use.

Doubts about radiation from shortened antennas can be resolved by
reference to "Terman`s "Radio Engineers` Handbook". On page 795 Terman
says:
"Top loading has the same effect on field distribution in a vertical
plane as a greater height."

Terman also says of a loading coil inserted in an antenna a little way
down from the top:
"This method of top loading gives results equivalent to those obtained
with a capacity top."

Maybe a flat coil is more equal than a solenoid. Were it of great
importance, Terman would have told us.

Best regards, Richard Harrison, KB5WZI

Richard Harrison wrote,

Maybe a flat coil is more equal than a solenoid. Were it of great
importance, Terman would have told us.


A flat coil should work fine as a capacitance hat.
73,
Tom Donaly, KA6RUH

A flat coil should work fine as a capacitance hat.

I have thought about trying this. With a spiral or flat coil you have a hat
and a loading coil all rolled up in one. Winding spiral coils is not easy, and
the mechanics of mounting on my mobile antenna have kept me from trying, but I
may yet. What do you think Tom?
73 Gary N4AST

Gary wrote,

A flat coil should work fine as a capacitance hat.

I have thought about trying this. With a spiral or flat coil you have a hat
and a loading coil all rolled up in one. Winding spiral coils is not easy,
and
the mechanics of mounting on my mobile antenna have kept me from trying, but
I
may yet. What do you think Tom?
73 Gary N4AST


Hi Gary,
it may not be worth all the work involved. I'm not an expert on
mobile antennas, so don't take anything I write on the subject too seriously.
On the other hand, there should be some current into the coil causing a
changing charge density at the other end which would, in turn, cause a
changing electric field in the vicinity of the antenna, which would cause
electromagnetic radiation, so you might see some improvement over
what you're using now, after all.
Try it out.
73,
Tom Donaly, KA6RUH

JGBOYLES wrote:
With a spiral or flat coil you have a hat
and a loading coil all rolled up in one. Winding spiral coils is not easy, and
the mechanics of mounting on my mobile antenna have kept me from trying, but I
may yet.

There was a magazine article a couple of years ago about such
in one of the ham rags - sorry, don't remember which one.
--
73, Cecil http://www.qsl.net/w5dxp



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Tdonaly wrote:
On the other hand, there should be some current into the coil causing a
changing charge density at the other end which would, in turn, cause a
changing electric field in the vicinity of the antenna, which would cause
electromagnetic radiation, so you might see some improvement over
what you're using now, after all.

If the pancake coil is in the horizontal plane, it will probably
radiate horizontally polarized radiation and probably straight up.
--
73, Cecil http://www.qsl.net/w5dxp



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Cecil wrote,

Tdonaly wrote:
On the other hand, there should be some current into the coil causing a
changing charge density at the other end which would, in turn, cause a
changing electric field in the vicinity of the antenna, which would cause
electromagnetic radiation, so you might see some improvement over
what you're using now, after all.

If the pancake coil is in the horizontal plane, it will probably
radiate horizontally polarized radiation and probably straight up.
--
73, Cecil http://www.qsl.net/w5dxp



It might. Do you want to tell us why you think so, Cecil?
73,
Tom Donaly

Pancakes have been written about for a while in RADCOM of the U.K.
In Europe there is some experimenting going on below the
broadcast band but it is limited to a few watts.
The basket weave was mainly introduced to REMOVE the
intercapacitance of the coils and a capacity hat was
introduced immediately AFTER the inductor.
Because they were only using a few watts there was not a concern
regarding voltage breakdown, a concern that should be reviewed before
entertaining the idea at the end of a high powered whip !
Regards
Art



Cecil Moore wrote in message ...
JGBOYLES wrote:
With a spiral or flat coil you have a hat
and a loading coil all rolled up in one. Winding spiral coils is not easy, and
the mechanics of mounting on my mobile antenna have kept me from trying, but I
may yet.

There was a magazine article a couple of years ago about such
in one of the ham rags - sorry, don't remember which one.

Tdonaly wrote:
Cecil wrote,
If the pancake coil is in the horizontal plane, it will probably
radiate horizontally polarized radiation and probably straight up.

It might. Do you want to tell us why you think so, Cecil?

Just off the top of my head - since the coil exists essentially only
in the horizontal plane, the radiation from the coil is likely to be
horizontal. If it is mobile, it is a very low antenna. Very low
horizontal radiation usually tends to result in an NVIS radiation
pattern in the far field. Hope there are no bugs in that logic.
--
73, Cecil http://www.qsl.net/w5dxp



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Cecil wrote,

Tdonaly wrote:
Cecil wrote,
If the pancake coil is in the horizontal plane, it will probably
radiate horizontally polarized radiation and probably straight up.

It might. Do you want to tell us why you think so, Cecil?

Just off the top of my head - since the coil exists essentially only
in the horizontal plane, the radiation from the coil is likely to be
horizontal. If it is mobile, it is a very low antenna. Very low
horizontal radiation usually tends to result in an NVIS radiation
pattern in the far field. Hope there are no bugs in that logic.
--
73, Cecil http://www.qsl.net/w5dxp


The only way to be sure is to make or model this thing. I'd like to
make a point or two, though. 1. Since it's a coil, and a small one at that,
it would need current in order to make the B field which would produce
the horizontal E field which would define its polarity. The fact that it would
be
small and placed at the end of the antenna makes me think it would
be starved for current. 2. Since one end of the coil isn't attached to
anything, all it could do would be to accumulate and release charge. This would

create a changing E field, the lines of which, would end on the vehicle.
Since these lines would be roughly vertical, they might produce some
(probably undetectable) advantage in the radiation field. 3. A real
capacitance hat would probably do a much better job and be easier
to make. (How do you keep a flat coil from jiggling and
bouncing around like a clock spring as you're driving down the road?)
4. You might be better off thinking about ground losses in order to improve
your signal. Maybe a bigger truck would help.

73,
Tom Donaly, KA6RUH, COW (Certified Old Wife)