Tom Ring wrote:

And YO could beat K1FO by only hudredths of a dB. If he'd had more CPU
power to do more runs per day...

YO7 includes a model of K1FO's 40 element 70 cm Yagi. In YO7, it
measures:

Gain 20.93
F/R 24.01
Z 21.8 + j5.4
SWR 1.0
Gain FOM -0.4 (versus theoretical limit for a given boom length)

In 10k iterations (minutes on a 250 MHz Pentium II), YO7 produced:

21.24
19.54
20.9 + j46.1
1.0
0.0 (I stopped it when it reached this)

You can tweak for Gain, F/R, etc depending on how you weight
performance tradeoffs. Looking at the current distribution, it appears
fewer elements might result in a better design. YO7 does not optimize
for number of elements but it doesn't take much effort to remove
elements and see what happens on the same boom length.

Regarding K1FO's design using Basic on a PDP11, here's Brian's
description:

************************************************** *********************************
YO includes an automatic optimizer that can maximize
forward gain and input resistance, and minimize backlobes,
sidelobes, and SWR. The optimizer iteratively adjusts element
lengths and spacings to optimize performance objectives you
specify using parameter tradeoffs you decide. It can perform
both local and global optimization.

YO is calibrated to NEC, the reference-accuracy
Numerical Electromagnetics Code from the Lawrence Livermore
National Laboratory. YO and NEC results normally differ by less
than 0.05 dB in forward gain, a dB or two in F/B, and a couple
ohms in input impedance. You can invoke NEC from within YO to
verify results.

YO's analysis and graphics engines use assembly language
with pipelined floating-point code optimized for Pentium processors.
************************************************** **********************************

The entire yo.exe program is only 82k (and DSP Blaster is only 16k).
The major change from YO6 to YO7 was the addition of global
optimization, so it will not get stalled on local maxima.

The other thing I must give Brian credit for is his excellent command
of English. I have *never* seen a spelling or grammatical error in any
of his documentation, which is very unusual these days.

73, Bill W4ZV