> Hi, does anyone know the historical origin of the ZL-Special antenna? I
> have made one out of 300 ohm TV twin-lead and with the matching network I
> came up with, its SWR is 1:1 across the 17 meter band. Am wondering if
> this adaptation has ever been done before and would love to read anything
> I can get my hands on about this antenna.
The ZL special is a derivative of the W8JK array by John Kraus,
If you go to a library, look at Antennas by Kraus. The section
"Array of Two Driven 1/2 wavelength Elements. End-fire case."
covers this antenna and also a section on "flat-top beam".
The modification made in the ZL special was the offset of the
feedline resulting in cross-fire phasing. Too bad there aren't books
available in amateur radio that discuss cross-fire phasing in detail,
since it is superior in bandwidth and performance.
Cross-fire phasing was popularized by use in broadband TV
antennas. If you remember, Channel Master had a "Color-crossfire"
antenna that was very popular.
Log periodics are an offshoot of this, and I use that phasing method
in all my phased antennas including my four square arrays. You
are right, it is definitely better than traditional phasing methods.
73, Tom W8JI
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