John,
This antenna replaces traps or interlaced resonant elements or trap loading
for each band with motorized metal tape elements that crank out to half wave
on each element, for the band in use. It is an approach to do away with
trap losses.
However, it as I understand it, it does not adjust the element to element
boom spacing of this Yagi. Thus, the fixed spacing will be a compromise of
gain and front to back over a monoband Yagi. I think it would of necessity
be a bit lower in performance to Yagis which have individual elements for
the bands, such as Force 12 design. However, it keeps your profile to only
3 elements. Am not sure what the wind load implications of for the added
mechanical mechanism. My concern would be that in areas with freezing
winter rain and ice, the elements could get hung up, unless they are
enclosed adequately. And, would they be locked in length sufficiently to
withstand wind? What kind of lifetime do the small motors required have?
I guess the analogy would be to the screwdriver type antenna. But inside of
motorized tap changing on a coil, you are moving the actual element length.
A novel idea!
73,
Stuart K5KVH
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