RE: NEC-LIST: 4NEC2 Optimizer

Hi Brandon,

We used a Genetic Algorithm a number of years ago to optimize two types of
Yagi antennas. For the first application we optimized for gain only. We
used boomlengths from 3.6 to 6.1? at 432 MHz. We allowed both the lengths
and the spacing between elements to float and obtained simulated and
measured gains that were consistently higher than those that could be
obtained using a conventional design approach. This was reported in the
Winter 1998 issue of Communications Quarterly. The second application was
for a broadband Yagi with low sidelobes. This Yagi was simulated for 219 to
251 MHz for sidelobes below 25 dB. It was scaled and measured at 1310 to
1510 MHz. These results are included in a review article in the April 1997
issue of the Antennas and Propagation Magazine.

I was surprised that you kept your spacing and element length constant. I
suspect that you may have obtained a higher performance Yagi if you had
included these parameters in your optimization.

Best regards,

Ed Altshuler

-----Original Message-----
From: Brandon Orchard [mailto:brandon.orchard_at_poynting.co.za]
Sent: Wednesday, December 11, 2002 4:35 AM
To: neclist; mikes_at_signull.com
Subject: RE:NEC-LIST: 4NEC2 Optimizer

Dear Mike

I have optimised a couple of yagi's using SuperNEC's Genetic Algorithm
optimiser(some of my MSc work) and I have listed the results below. Most of
the results were nice and broadband with very good Gains and VSWR's .Please
contact me if you require any of the antenna parameters for any of the
designs listed.
All the yagi designs below use elements with a 0.008m radius, a folded
dipole feed, directors of all equal length, spacing between directors all
equal, and the design frequency was set to 300Mhz (you can always scale the
designs for the right operation frequency) .

-5 element yagi(vswr for 75ohms)
Gain BW 22.3% VSWR<2 BW 8.7% gain @ 300Mhz 10.19dBi
Gain BW 21.7% VSWR<2 BW 5% gain @ 300MHz 10.4dBi

-6 element yagi (VSWR for 75ohms)
Gain BW 14% VSWR<2 BW 5.7% gain @300MHz 11.62dBi

-12 element yagi (VSWR for 200 Ohms)
Gain BW 29.3% VSWR<2 BW 20% gain @300MHz
12.11dBi

-15 element yagi (VSWR for 200 Ohms)
Gain BW 11.3% VSWR<2 BW 11.3% gain @ 300MHz 15.38dBi
Gain BW 14% VSWR<2 BW 12.7% gain @ 300MHz 14.61dBi

-17 element yagi (VSWR for 200Ohms)
Gain BW 15.7% VSWR<2 BW 11% gain @ 300MHz 14.59dBi
Gain BW 17.3% VSWR<2 BW 12.7% gain @300 MHZ 13.97dBi

where %gain BW = ((Fh-Fl)*100)/Fc
where Fc=300MHz(design frequency) Fh=highest frequency at which gain is 3dB
lower than gain at Fc and
Fl=lowest frequncy at which gain is 3dB lower than gain at Fc

Regards,
Brandon

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