On Fri, 14 Mar 2008 10:09:42 -0500, (Richard
Harrison) wrote:

Mike, N3LI wrote:
"There appears to be one device (two maybe?) and it is in the hands of a
snowbound ham in the great north."

Build a small scale model that can be tested indoors and report its
characteristics. Antennas are scaleable.

Hi Richard,

A scaled model of an antenna the size of two shoe boxes? Gives new
meaning to the toys kids used to collect called "matchboxes."

If going from 160M to half a meter was achievable, then going to a
couple of centimeters should be a walk in the park. If scaling down
300 times was achievable and saw great boon, then scaling down another
tenth must bring even more efficiency gains.

Why was this option left on the table when it results in a vastly
simpler construction and a superior product?

Something tells me NO ONE knows why.

73's
Richard Clark, KB7QHC

Richard Clark, KB7QHC wrote:
"Something tells me NO ONE knows why."

The technique works. Before erection we had a newly designed 6&7 MHz
curtain antenna modeled in the lab at 450 MHz, about a freq. ratio of
70. The as-built antennas were measured and found to perform exactly as
predicted by the scaled-down version.

Cecil`s question about continuously loaded antennas is appropriate. I
suspect the wire size needs to be modeled too, but Cecil knows much more
about loading coils than I do.

Best regards, Richard Harrison, KB5WZI

Richard Harrison wrote:
Cecil`s question about continuously loaded antennas is appropriate. I
suspect the wire size needs to be modeled too, but Cecil knows much more
about loading coils than I do.

I doubt that, Richard. When the length of a dipole is
much, much greater than the diameter of the wire, the
antenna will scale appropriately. But what happens when
the length of the antenna is not a lot greater than the
diameter of the wire?

It is the same problem as trying to use water in scale
models of boats. It just doesn't work.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
"When the length of a dipole is much, much greater than the diameter of
the wire, the antenna will scale appropriately.

Yes. An assumption made to ease calculations is that the diameter of the
radiator is vanishingly thin. Art`s antenna configuration is something
of a mystery to me but I infer that it may be a dipole in which the two
lengths of wire have been wound into coils and not extended to their
maximum length. Further, my guess is that the dipole is resonant so that
it readily accepts energy. Such antenna elements, I believe usually emit
energy in the radial mode and resemble the continuously loaded vertical
antenna as shown on page 6-28 in the 20th edition of the ARRL Antenna
Book.

Description of the resonant element includes:
"The relationship between length of wire needed for resonance and a full
quarter wave at the desired frequency depends on several factors. Some
of these are wire size, diameter of the turns, and dielectric properties
of the form material to name a few. Experience has indicated that a
section of wire approximately one half wavelength long, wound on an
insulating form with a linear pitch (equal spacing between turns) will
come close to yielding a resonant quarter wavelength. Bill Orr says
about the same thing on page 78 of "Vertical Antennas". Continuing from
the Antenna Book: "Therefore, an antenna for use on 160 meters would
require approximately 260 feet of wire spirally wound on the support."

If Art has made a dipole of two such 1/4-wave elements, it should have
about a full wavelength of wire which I believe is consistent with his
miserly description.

Performance of a full wave of coiled wire will be much less than the
performance of the same wire stretched out into a straight line at the
same height above earth.

Best regards, Richard Harrison, KB5WZI