I was reading up on the above antenna which is a take off
of an antenna I patented ,( Constant Impedance
Matching System) and written up in QST March, 1998
I also described this system in earlier postings on this
newsgroup.
Those who use this antenna should look at moving the
extra director back closer to the driven element as the
constant impedance is drawn not from the inferred
increased diameter of the driven element but from the
change over power point between the two close
radiators which changes as frequency changes,
i.e. the cross over point is related to the matching
impedance point.
(Coupling distances measured as low as 1 mm have
been used successfully with mylar as an interface)
There is absolutely no reason why this matching system
should not be used more extensively where the search
for gain has resulted in shortened bandwidth where
the addition of this matching system has allowed for
increases in gain.
( It should be noted that as the frequency is raised
the input impedance requires extra inductance and
capacitance for a better match and thus moves further
along the radiator before tranference to the coupled
antenna)
ART