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

David wrote:
Can someone explain to me how a new antenna design is started. Do you
take an initial standard design and then enter it into a modeling
program and optimize it for the required parameters ?

Is there a suitable reference book that would explain this process. I am
thinking about the Cebik antenna modeling book but think this may only
cover how to model and change an existing design,would it cover how to
come up with the initial design in the first place ?

Example: Say I want to design a 4 Element Yagi at 921 MHz using 6mm
diameter elements.

Is there a standard formula that would be used to calculate initial
lengths and distances between elements. Then you enter this design into
say EZNEC and use the optimizer to tweak the design.

Thanks in advance

Regards

David