Antenna physical size
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
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