Is there in existence or has anyone ever thought or is there any possible
usefulness in a rating system for yagi antennas? You ascribe a value to
each of the main the characteristics and you publish the rating along with
the design.

Virtually all the latest Yagi-Uda work is aided by simulation and computer
optimization. This is assessed through a 'cost function' (also known as figure
of merit; objective function) which is a mathematical formula that weights
bandwidth; gain; feed impedance; F/B and so on.

There is no 'one' cost function, and tailoring it requires some finesse. The
tradeoff usually occurs in bandwidth compared to gain and F/B. The bigger the
value of the cost function, the better the candidate design.

A simple expression that could be used is

CF= aG +bF +cW (1)

where G is gain in db; F is F/B in dB; and W is bandwidth in percent. the
a,b,c coefficients thus determine which is a bit more important to you, as
well as allowing relative normalization.

73,
Chip N1IR