There's yet another tradeoff -- bandwidth, of both the pattern and the
impedance. Close spacing, in particular, reduces the range of
frequencies over which the pattern is acceptable ("acceptable" being in
itself subject to compromise) and over which the SWR is acceptable. But
close spaced or not, it's much easier to tweak a design to work
perfectly at a single frequency than make one that will retain some
semblance of that perfection over a wider range of frequencies.

Roy Lewallen, W7EL

Richard Harrison wrote:
Art Unwin wrote:
"But my main question still remains a pointer to a technical article
that discusses the possibility or impossibility of what I have stated."

I don`t get the question, but it seems to me, Art wants to know if
anyone has written of a method to make maximum gain correspond with
maximum front-to-back ratio in a Yagi.

I haven`t seen it. There is a third factor in the compromise, 50-ohm
feedpoint (or some other convenient impedance).

Kraus gives the Yagi-Uda story in "Antennas" There has been much
experimentation and the tradeoffs still exist. Don`t close the patent
office yet. Almost everything can be improved. Art may be implying that
he thinks he has a way to make a better Yagi. I hope so.

The "ARRL Antenna Book" is a good place to see where the art was at the
time of publication. The Antenna Book devotes a chapter to the Yagi, No.
11 in my 19th edition. The directional patterns show a pair of
troublesome sidelobes in addition to the mainlobe. It`s the sidelobes
which are suppressed at the sacrifice of a little gain. Parasitic
arrays are close-spaced for significant excitation. Close-spacing means
close-coupling which lowers the drivepoint impedance. It`s a tradeoff
again because low impedance eventually limits the antenna`s efficiency.

Best regards, Richard Harrison, KB5WZI