Someone at work designed a 240 GHz corrugated horn for
me using internally developed EM computer codes. The
dimensions were sent to a local vendor who direct machined
the corrugations using a CNC lathe. The simulated patterns
agreed with the measured patterns down to the -40dB level.
The agreement between computer simulation and measured
data was in fact remarkable (you could hardly tell the two
curves apart). Of course from what I understand, this sort
of thing is routine for these EM folks.
73 de Mike, W4EF.........................
----- Original Message -----
From: "2" <2@vc.net>
To: <g0ruz@btinternet.com>; " AMPS" <amps@contesting.com>
Sent: Saturday, July 27, 2002 10:56 PM
Subject: RE: [Amps] Muffin Fan on Swan Mark 1
>
>
> >
> >
> >-----Original Message-----
> >From: 2 [mailto:2@vc.net]
> >Sent: 27 July 2002 16:04
> >To: g0ruz@btinternet.com
> >Subject: RE: [Amps] Muffin Fan on Swan Mark 1
> >
> >
> >>Sure but fwd gain is important in moonbounce. The trouble with computer
> >>apps is that are created by humans.
> >
> >Ahh now there's where you are wrong, what is important in eme is G/T
which
> >is a combination of gain and antenna noise temperature, these days noise
> >temperature optimisation is what gives you the best performance on the
eme
> >circuit. Of course the best yagis have excellent gain coupled with a very
> >clean pattern and all of them have been computer optimised. In this case
> >computer optimisation works really well and of course the test range and
the
> >eme path prove it. I totally agree however that it computer modelling is
a
> >poor substitute for the real thing. In the case of yagis had Yagi-Uda not
> >given DL6WU something to start on we would be nowhere. DL6WU used the
test
> >range to "tweak" his antennas and then DJ9BV,K6MYC etc took the DL6WU and
> >really optimised it, this saved many hours and lots of metal. I doubt
very
> >much whether we will improve the yagi any further.
> >I have been on 144 and 432 eme since 1990 BTW.
>
> Interesting. thanks.
>
> About 20-years ago, John McDonald, W6SDM built an 11-el 432MHz yagi-uda
> with adjustable matching, element length, and spacing on a non-conductive
> boom. He tried the various publish designs. He arrived experimentally
> at optimal gain compared to an NBS reference antenna. My guess is that
> was little room left for improvement.
>
>
> cheers, Conrad
>
> - R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
> www.vcnet.com/measures.
> end
>
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