On Wed, 11 Jan 2006 18:53:06 -0800, Roy Lewallen
wrote:

A very good source of starting designs is _Yagi Antenna Design_ by James
Lawson, W2PV, published by the ARRL. It clearly illustrates the various
tradeoffs which can be made in Yagi design, and gives lots of
alternatives. There is no "ideal" design, since there are so many
tradeoffs to be made -- gain, front/back ratio, bandwidth, size, which
you can't maximize all at once.

EZNEC doesn't have an optimizer -- if you use EZNEC you have to tweak
the design yourself. People who have used optimizing programs have told
me they've often been able to improve on the "optimized" design by hand
tweaking with EZNEC.

Roy Lewallen, W7EL

I second Roy's recommendation and add one. If Yagi antennas are the
interest then in addition to Lawson, you need Leeson; "Physical Design
of Yagi Antennas", by David Leeson, W6QHS.

It is not enough to come up with a super-duper electrical design if
you can't actually assemble it or keep it in the air after it's
assembled.

For example many "optimized" or "fifty-ohm feedpoint" designs are so
mechanically unbalanced that they put a large unbalanced strain on the
rotator if mounted near the boom center. If mounted at a static
balance point they turn into a windcock and damage the rotor from that
stress.

So a well engineered antenna is one that not only performs well from a
gain, FB and SWR standpoint, but is also easy on the tower and rotator
and will last years in the air without degradation.