Ian White GM3SEK wrote in news:6O1lIpHoLZzKFAM3
@ifwtech.co.uk:

....
[1] All credit to DK7ZB for making the point that it's much easier to
design high-performance yagis with a feedpoint impedance in the region
of 25-30ohms. He feels that increasing the feedpoint impedance to 50
ohms (eg by adding a closely-spaced first director) makes optimization
more difficult, ...

Absolutely, and designing an effective, efficient, reproduceable matching
arrangement is an essential part of system design.

Whilst I have reservations about the design pics etc referenced, the
fundamentals of the Yagi itself look good, and with an impoved matching /
balun element, it looks like a practical high performance antenna. They
are certainly becoming more popular in this part of the world where most
home brew designs are DL6WU based (for good reasons, but peformance isn't
the principle goal).

An improved design could persue a more reproduceable balun that had an
adequately high shunt impedance on one side of the DE, or better, a
symmetric balun, and the shunt impedance was tuned out as part of the DE
tuning adjustment. The latter, if done properly, should result in more
symmetric current distribution on the DE, and pattern closer to that
modelled.

On that point, I am often somewhat amused at the out of hand dismissal of
gamma matches because of pattern distortion, and recommendation of
asymmetric baluns in their place. Symmetric baluns are just not very
popular with hams on VHF and UHF.

Owen