Re: Antenna optimizers
- From: "art" <aunwin@xxxxxxxxxxxxx>
- Date: 9 Mar 2007 06:18:03 -0800
On 9 Mar, 02:37, Ian White GM3SEK <gm3...@xxxxxxxxxxxxx> wrote:
In a different thread, N5MK wrote:
I've tried some programs with "optimizers" etc, etc.. MMANA has one fer
instance, and it's freeware. In many cases, I can manually churn out a
better design by ignoring it, and doing it myself. I've seen a few
churn out some pretty funky designs which were not even close to being
optimum. Overall, I don't have much use for them. I don't need the
program to hold my hand while using it.
Can we start a new discussion, specifically about optimizers?
Having used Brian Beezley's YO and AO (Yagi Optimizer and Antenna
Optimizer) extensively in the past, I'm not quite as pessimistic as Mark
about the value of optimizers.
If they're simply allowed to run wild, they can produce some very
foolish antenna designs. Usually that is not a criticism of the
automated modeling... it mostly means that, for some practical reason or
another, the user would be a fool to build the thing.
On the other hand, an optimizer can be very useful for tasks that have a
very simple target, so it can't go far wrong. For example: "Adjust the
length of that wire to make it resonant at this frequency." That doesn't
take long to do by hand, but an optimizer can also handle more
complicated tasks like: "Adjust the lengths of these three interacting
wires to make the antenna resonant on three different bands." Then you
really start to see some benefit from the automation.
At the other end of the spectrum is the kind of complex optimization for
which YO was developed. You quickly learn that you can't just say
"Optimize that yagi!" Quite the opposite: to use the program at all, you
are forced to think very hard about what you really mean by "optimum" -
for example, how much importance you attach to forward gain, a clean
pattern, a convenient feedpoint impedance, and to maintaining that good
performance over a wide bandwidth. Playing with an optimizer, you
quickly come to understand that it isn't possible to get the best of
everything, all at the same time... which is a very valuable lesson to
learn.
The same applies to all other antenna optimizers, of course; and circuit
optimizers too. The learning process alone can be worth the money.
Having gone through that learning process, an automatic optimizer can
then zip out some really good antenna designs in a matter of minutes -
which leaves you wondering what took you so long :-) But that isn't
going to happen in the first evening, or even maybe the first month.
[Sorry, I don't know how or even if you can buy AO or YO any more.]
--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)http://www.ifwtech.co.uk/g3sek
What bothers me about all this Ian is that AO when allowed to run
freely
does produces an array where all elements are resonant in situ.
Put this same array in NEC4 and the program will concur with the value
of the desirables given. In the early days I thought that this was a
result of programming interference by outsiders but the symetry kept
bugging me. So I gave a rational for why AO was correct to test the
water. Well we all know that it is not in the books therefore I am an
idiot. So we flip the coin and determine why the original NEC code
provided an opening for such a big error but first we determine if
this so called"" error" had spread in any way.
Tho I believe my rational is correct surely the majority would be
interested in the cause of this anomaly, why it produced antenna
arrays that were legitametly smaller than the yagi and since NEC4
verified its performance it should be of interest to all antenna
designers. But no.
Ridicule has been put into motion and true science went out of the
window.
Cheers
Art
Go figure!
.
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- From: Ian White GM3SEK
- Antenna optimizers
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