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)