I have not modeled the "ZL Special", but it's obviously a Log-Yagi with 2-Element LPDA driven pair and
a bunch of passive directors (and NO reflectors????). A Log-Yagi CAN be better than the sum of its parts:
http://www.hamuniverse.com/gi6jpozl-special.pdf
If you were to simply rescale it to Hi-VHF or UHF bands, it probably would cover only a few channels.....
W-G YA-1713 is a Log-Yagi with 2-Element LPDA driven pair, a reflector and 7 directors.
RCA ANT-751 is a Log-Yagi with 2-Element LPDA driven pair for Hi-VHF, NO reflector and 2 directors.
Although Raw Gain is believable, I ran into difficulties trying to calculate SWR for both using 4nec2.....
Cebik has some articles re "Log-Cell Yagis" here:
http://www.cebik.com/content/radio.html
FREE Registation required to access....
There is a DOS based design program LOGYAGI.EXE you might want to take a took at,
but be sure to run any downloaded software through a virus check program....
BTW: I found LOGYAGI.ZIP which contained a RUSSIAN spread sheet....but it was LPDA, not LogYagi.
The difficulty with DIY designs, whether standard Yagi or Log-Yagi, is determining the
OPTIMUM design parameters....the big boys use optimization routines to "find" a solution
that provides good Gain and F/B Ratio across the entire band....not an easy accomplishment.....