"Fractenna" wrote in message
...
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


I was thinking that for every published or generic design maybe there could
be a kind of master list that you could consult.

ie like:
Rating
Antenna Gain F/B Bandwidth

OWA (5 ele) 3 3 5

Standard Yagi (5 ele) 4 3 2

DL6WU (10 ele) 5 6 2

DL6WU (15 ele) 6 6 2

But, you could just use the actual values I suppose. You would have in this
case three seperate tables, this one above if low to high on the gain
parameter.