I've played with parasitic elements in antenna arrays for almost three
decades and the current antenna system I have used parasitic elements
both director and reflectors.
With very careful tuning performance that of a all driven array can be
achieved. Tree is correct they due tend to be somewhat limited in in
bandwidth with relation to F/B ratio. Gain remains fairly constant.
The tuning procedure that Tree suggested is absolutely correct. You
detune all unused elements and adjust the center frequency of the
parasitic for best F/B one element at a time. Parasitic elements I might
add are no different than driven and must have extensive ground system
to be effective. No exceptions. You know you have right by F/B ratio.
You can go one step further and measure the actual antenna currents
which I have done. In my system the parasitic elements achieve 80-85% of
the theoretical current at the base.
de Bob W7RH
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W7RH DM35OS
It has become appallingly obvious that our technology has exceeded our humanity.
Albert Einstein
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