PARASLEEVE ANTENNA ELEMENTS
Parasleeve antenna elements refers to a means of using
multiple parallel coupled elements to achieve multiple
resonances without the use of traps or stubs.
Generally, the longest element (lowest frequency) is
chosen as the directly fed element and higher frequency
elements are added parallel to the main element. Coupling
(spacing) is adjusted to provide a second (and third) match
on the desired higher frequencies.
This is the technique that allows the Force 12 antennas to
provide 3 full size driven elements without traps and only one
feedline in their C3 series of antennas. A continuous 15M
parasleeve element is placed behind the 20M split dipole
and a continuous 10M parasleeve element is placed in front
of the 20M driven element.
One disadvantage of parasleeve elements is that the coupling,
and therefore SWR, changes when the elements vibrate out of
their normal resting position, such as when the wind blows.
Some sort of insulated spacer may help to reduce this effect.
There was an acticle in QST describing a parasleeve vertical
for 40, 20, 15, 10 meters, configured in a square pattern.
I am not aware of anyone making a 5 band parasleeve
driven element yet, but that would seem to be an ideal
means to cover 20, 17, 15, 12, 10 meters combined with
separate reflectors for each band, spaced at 0.15 WL or so.
Would the first commercial manufacturer of this idea please
send me a "sample" for evaluation? :-)
de Tom N4KG
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