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<HTML>
<BODY>
<PRE>
<!-- Manpage converted by man2html 3.0.1 -->
</PRE>
<H2>NAME</H2><PRE>
optimise - Yagi-Uda project antenna optimiser
</PRE>
<H2>SYNOPSIS</H2><PRE>
<B>optimise</B> [ -<B>dhvwO</B> ] [ -<B>a</B><I>angular</I>_<I>stepsize</I> ] [
-<B>b</B><I>boom</I>_<I>extension</I> ] [ -<B>c</B><I>cleanliness</I>_<I>of</I>_<I>pattern</I> ] [ -<B>e</B><I>elements</I>
] [ -<B>f</B><I>FBratio</I> ] [ -<B>g</B><I>GA</I>_<I>optimisation</I>_<I>method</I> ] -<B>l</B><I>percent</I> ] [
-<B>m</B><I>min</I>_<I>offset</I>_<I>from</I>_<I>peak</I> ] [ -<B>o</B><I>optimisation</I>_<I>criteria</I> ] [ -<B>p</B><I>po-</I>
<I>pulation</I> ] [ -<B>r</B><I>resistance</I> ] [ -<B>s</B><I>swr</I> ] [ -<B>t</B><I>length</I>_<I>tolerance</I> ]
[ -<B>x</B><I>reactance</I> ] [ -<B>A</B><I>Auto</I>_<I>gain</I> ] [ -<B>C</B><I>Currents</I>_<I>similar</I> ] [
-<B>F</B><I>weight</I>_<I>FB</I> ] [ -<B>G</B><I>weight</I>_<I>gain</I> ] [ -<B>K</B><I>keep</I>_<I>for</I>_<I>tries</I> ] [
-<B>P</B><I>weight</I>_<I>pattern</I>_<I>cleanliness</I> ] [ -<B>R</B><I>weight</I>_<I>resistance</I> ] [
-<B>S</B><I>weight</I>_<I>swr</I> ] [ -<B>T</B><I>position</I>_<I>tolerance</I> ] [
-<B>W</B><I>Weighted</I>_<I>algorithm</I> ] [ -<B>X</B><I>weight</I>_<I>reactance</I> [ <B>-Z</B><I>Zo</I> ]
filename iterations
</PRE>
<H2>DESCRIPTION</H2><PRE>
The program <B>optimise</B> is one of a number of executable pro-
grams that forms part of a set of programs, collectively
known as the <I>Yagi</I>-<I>Uda</I> <I>project</I> , which were designed for
analysis and optimisation of Yagi-Uda antennas. <I>optimise</I>
attempts to optimise the performance of a Yagi antenna for
one or more parameters that are considered important, such
as gain, F/B ratio, VSWR etc. It does this by randomly
changing the lengths and positions, of one or more elements,
then comparing the performance before and after the change.
Any improvements are written to a new file called
<I>filename</I>.<I>bes</I> where filename is the name of the antenna
description file created by <I>input</I> or <I>first</I>
When Yagi's are designed on paper, or using this program,
its possible that they will be almost impossible to build,
if their performance depends too critically on the dimen-
sions. To determine if this is the case with a design, we
run optimise with just the options 't' and 'T'. These
specify the tolerance with which you can build the antenna,
expressed as a standard deviation in mm. In this case,
instead of trying to optimise a poor design, optimise will
calculate the minimum gain, maximum VSWR, and minimum FB
ratio of a number of designs, all slightly different from
the input file. 99.7% of the components lie within 3 SD of
the mean, so if you think you can cut elements to with 1 mm
99.7% of the time, specify t0.33. If you can put them in the
boom to within 3 mm 99.7% of the time, specify T1.
If while <I>optimise</I> is running using the methods that require
weights to be attached to the gain, FB, SWR etc, it becomes
apparent, the weights are not optimum, its possible to pause
the program and re-adjust the weights. If a file with the
name of <I>changes</I> is created, the program will pause, then
request new weights are entered at the keyboard.
</PRE>
<H2>AVAILABILITY</H2><PRE>
</PRE>
<H2>OPTIONS</H2><PRE>
-<B>d</B> Print the default values of all the configureable
parameters to stdout. Typing this option with any
option that changes a parameter (see below) will
display the new value of the parameter, rather than the
default.
-<B>h</B> Print a help message.
-<B>v</B> Print verbose status information.
-<B>w</B> Instead of optimising at one fixed frequency (the
design frequency), this directs the program to optimise
at 3 separate frequencies (lowest, design and highest)
then to average data at all 3. This option is better
for wideband antenna. Note that the input impedance
printed is at the design frequency, *not* averaged over
3 frequencies. Averaging an impedance, is likely to
give a very misleading impression. The impedance aver-
aged over 3 frequencies can be 50+i0 Ohms, even if the
VSWR is very poor over all 3 frequencies, as the fol-
lowing 3 pieces of data show.
Z=147 + j 300 SWR= 15.46:1
Z=2 + j 100 SWR= 125:1
Z=1 - j 400 SWR= 3250:1
note in the above three cases, the average impedance is
50 + j 0, but average SWR is 1130:1.
-<B>O</B> Over-optimisation allowed. By default, the program
does not over-optimise a parameter. For example, an SWR
of 1.01 is usually considered good enough and any
change, as long as the SWR stayed good, typically below
1.1:1, would be allowed, even if the SWR rose. By
default, FB's of 27 dB, VSWR's of 1.1 are acceptable.
However, by using the -<B>O</B> option, you can insist the
program always improves things, no matter how good they
are.
centage by setting <I>boom</I>_<I>extension</I> to whatever you wish.
-<I>b30</I> will limit the boom to no more than 30% more than
the original length.
-<B>c</B><I>cleanliness</I>_<I>of</I>_<I>pattern</I>
Specify the number of dB down on the peak gain to aim
to get the pattern. Any antenna pattern cleaner than
this will not effect the fitness, nor will it be con-
sidered any better when comparing to antenna designs.
20 dB seems reasonable, so the default is 20, but this
may of course change if it's deceided too. Check the
source code to be certain (see REASONABLE_SIDELOBE in
yagi.h).
-<B>e</B><I>elements</I>
is an integer which specifies the type of elements that
are changed in the optimisation cycle. Possible values
are:
1 - alter only the driven element(s) length (useful to
bring to resonance)
2 - alter only the driven element position. Don't
change its length.
4 - alter only the reflector length. The position is
always at x=0.
8 - alter only the director lengths. Don't change
positions.
16 - alter only the director positions. Don't change
lengths.
32 - randomly adjust one element length, then makes
all other the same. Don't change the positions.
64 - apply a linear taper to the lengths.
128 - Set the driven element to a resonate length. It
may/may-not be altered after the first run, depending
on the whether or not '1' is invoked too. Eg -e128
will make it resonate and keep it there forever. How-
ever '-e129' will bring to resonance, then alter to
maximuse performance.
The elements altered is made from a logical AND of the
above, so for example to alter everything, except the
driven element length, use -e30, since 2+4+8+16=30. The
default is equivalent to -<I>e31</I> , which changes everything
possible. Note the reflector position is *never*
changed. It's always at x=0.
greater than <I>FBratio</I> dB to be equal to <I>FBratio</I> dB. This
avoids optimising to a very high FB ratio, which is
impracticable, as the bandwidth over which this FB
ratio will be maintained is very small and mechanical
considerations will prevent you from constructing it
with such a high FB ratio anyway. If this was not
prevented, you might just happen to get an antenna with
100 dB FB ratio, but poor gain and swr. Since by
default all parameters must improve, the optimisation
routine will most likely never being able to improve on
the 100 dB FB ratio, so no improvement will result.
Most people would prefer to get a few extra dB of gain,
even if the FB ratio dropped to 30 dB.
-<B>g</B><I>GA</I>_<I>optimisation</I>_<I>method</I>
Use a genetic algorithm. With the genetic algorithm,
the program does not take any account any of the ini-
tial lengths/positions of elements specified in the
input file. Rather it works by initialising a number of
different antenna, then computing a 'fitness' value for
each. The fitness value can depend on the gain, FB,
real part of the input impedance, reactive part of the
input impedance, VSWR or the level of the sidelobes.
The integer after the g tells the optimiser what to
consider. -g1 Use gain
-g2 Use FB
-g4 Use R
-g8 Use X
-g16 Use the SWR
-g32 Use the level of the sidelobes.
You can use a logical AND of these, so for example -g49
will use a genetic algorithm, optimising for gain, swr
and sidelobe level, since 1(gain)+16(SWR)+32(sidelobe
level)=49.
-<B>l</B><I>percent</I>
is a parameter (floating point number) which specifies
the maximum percentage change in the positions or
lengths of an elements at each iteration. If the option
is not used, it will be set internally at 10% for the
first 25% of the iterations, 1% for the next 25%, 0.1%
for the third 25% of the iterations and 0.01% for the
last 25% of the iterations. If set to a positive number
x (eg optimise -l 0.3 145e10) then the percentage will
be set at x% for 25% of iterations, x/10 for the next
25%, x/100 for the next 25 and x/1000 for the last 25%.
If set to a negative number y (eg optimise -l -0.5
145e10) then the paramters will stay fixed at y% (in
this example 0.5%) all the time.
-<B>m</B><I>min</I>_<I>offset</I>-<I>from</I>_<I>peak</I>
Sets the minimum angle in degrees offset from theta=90
degrees, where the side lobes start and the main lobe
finishes. The higher the gain, the smaller it should
be. It is set internally if not set on the command
line.
-<B>o</B><I>optimisation</I>_<I>criteria</I>
1 - Assume better if the gain has increased.
2 - Assume better if the front to back ratio has
improved.
4 - Assume better if the real part of the input
impedance is closer to the value that the program was
compiled for, or set using the '-Z' option. This will
usually be 50 Ohms, but you may wish to set this to
12.5 Ohms if you use a 4:1 balun. Generally you can
get higher gain from a Yagi if you allow the input
impedance to fall, but of course feeding it becomes
more difficult.
8 - Assume better if the magnitude of the reactive
component of the input impedance is lower (ie. the
antenna is nearer resonance).
16 - Assume better if the VSWR is lower.
32 - Assume better if the level of all sidelobes is
lower.
The <I>optimisation</I>_<I>criteria</I> may be formed from a logical
AND of these numbers, so for example choosing -<I>o19</I> will
only consider a revised antenna better than the previ-
ous, if the SWR, gain and F/B ratio have all simultane-
ously improved.
Clearly an antenna which originally had 12 dB gain and
1.01:1 VSWR but then changes to 20 dB gain @ 1.02:1
VSWR, would to most people be better, even though the
VSWR has increased. By default, <I>optimise</I> only optimises
to sensible maximums, so to not let the optimisation
stall prematurely. By running <I>optimise</I> with no argu-
ments, the program will list the limits of acceptabil-
ity. These might be typically F/B ratio > 27 dB, VSWR <
1.1:1, magnitude of input reactance less than 5 Ohms and
the real part of the input impedance within 5 Ohms of
Zo. Choosing -<I>o19</I> (1+2+16=19) will optimise for gain
(since G=1), FB (since FB=2) and SWR (Since SWR=16), but
would consider a higher gain and FB ratio antenna better
than a previous one, even if the SWR rose, as long as it
stayed below 1.1:1 (or as was set during compilation).
The default behaviour (no options) is equivalent to -<I>o37</I>
which optimiseas for <B>gain(1)</B>, the real part of the input
<B>impedance(4)</B> and <B>sidelobes(32)</B> but this may be changed
at any time, so type <I>optimise</I> -<I>d</I> to check the current
settings. If you insist on the program optimisang for
the very best of all selected parameters, use the -O
option too, but be warned the optimisation will probely
stick once it gets one parameter really good.
-<B>p</B><I>population</I>
This determines the initial population used with the
genetic algorithm.
-<B>r</B><I>resistance</I>
When optimising an antenna, consider any input resis-
tance closer to Zo (usually 50 Ohms) than <I>resistance</I>
Ohms to be acceptable. This avoids optimising to an
input resistance too close to Zo, which is impractica-
ble, as the bandwidth over which the input resistance
could be maintained is very small and mechanical con-
siderations will prevent you from constructing the
antenna with such an ideal input resistance. If this
was not prevented, you might just happen to get an
antenna with an input resistance of 50.000001 Ohms, but
poor gain, FB and possibly even a poor swr, if the
antenna is well away from resonance. Since by default
all parameters must improve, the optimisation routine
will get most likely never being able to improve on the
antenna, whereas we might be happier with a few more dB
gain, if the input resistance went to 50.1 Ohms. It
should be noted that the default optimisation routine
never uses the input resistance directly (only VSWR),
so this option cant be used without the '-o' option to
optimise for other than the default parameters (gain,
VSWR and FB ratio).
-<B>s</B><I>swr</I>
When optimising an antenna, consider any SWR less than
<I>swr</I> to be equal to <I>swr</I> This avoids optimising to a very
low swr, which is impracticable, as the bandwidth over
which such a low swr could be maintained would be very
small and mechanical considerations will prevent you
from constructing such an antenna anyway. If this is
was not prevented, you might just happen to get an
antenna with an swr of 1.000000000001:1, but poor gain,
FB ratio. Since by default all parameters must improve,
the optimisation routine will most likely never being
able to improve on the antenna, even though in practice
you would like to get a few extra dB of gain if the SWR
would rise to 1.02:1. The default was equivalent to -
<I>s1</I>.<I>1</I> but run <I>optimise</I> -<I>d</I> to display this and any other
defaults.
-<B>t</B><I>length</I>_<I>tolerance</I>
<I>length</I>_<I>tolerance</I> is the standard deviation in mm of the
accuracy with which you can cut elements. Since 99.7%
of elements will be with 3 standard deviations of the
mean length (stats theory says this), set -t0.2 if vir-
tually all (well 99.7%) of elements are within
3x0.2=0.6 mm of the correct length. This option *must*
be used with the '-T' option and can't be used with
any other options apart from
-<B>x</B><I>reactance</I>
When optimising an antenna, consider any input reac-
tance of less than <I>reactance</I> to be <I>reactance</I>. This
avoids over optimising the reactance, at the expense of
something else.
-<B>A</B><I>auto</I>_<I>gain</I>
When the <I>auto</I>_<I>gain</I> option is used. the program maximes
the gain of the antenna (ignoring all other parameters
such as SWR, FB ratio etc) by adjusting the length (not
position) of one element only. -A-1 will maximuse the
gain, by adjusting the length of the reflector, -A0
will maximise the gain by adjusting the length of the
driven element. Its generally *not* a good idea to max-
imise the gain by adjusting the driven element, but the
program lets you do it, but using the option -A0. Using
-A1 will maximise gain by adjusting the length of the
first director, -A2 the second director and so on, up
to the last director. You must check carefully that the
input impedance in particular does not fall to silly
values if you use this option. On a yagi with many ele-
ments (> 10 or so), you can pretty safely maximise the
8th or more director, but doing it on the reflector,
driven element or early directors often leads to silly
input impedances - so beware! Note, no matter how many
iterations you specify, this process is only done
once.Its unlikely you will be able to do it again,
without things going out of hand, but if you must do
it, you must re-run 'optimise' again.
-<B>C</B><I>currents</I>_<I>similar</I>
If this option is used, where <I>currents</I>_<I>similar</I> is an
integer, the program looks to make the currents in the
last <I>currents</I>_<I>similar</I> elements as similar as possible.
It computes the sum of the squares of the deviations of
the absolute values of the element currents from the
mean. If this falls, and the criteria specified with
the -W option is also satisfied, the antenna is con-
sidered better. If <I>currents</I>_<I>similar</I> is three less than
the number of directors, it tries to make the currents
in the the directors (but ignoringing the first 3) all
similar. If <I>currents</I>_<I>similar</I> is equal to the number of
directors, it tries to make all the directors have
similar currents. If <I>currents</I>_<I>similar</I> is one more than
the number of directors, it tries to make all the
directors and the reflector have similar currents. If
<I>currents</I>_<I>similar</I> is equal to the total number of ele-
ments, then it fails with an error message.
-<B>F</B><I>weight</I>_<I>FB</I>
is the floating point number (default 1.0) specifying
the weight to attach to the FB ratio of the antenna
when using the '-W' option, which calculates a fitness
for the antenna based on one or more parameters (FB,
gain, input resistance, input reactance, SWR, cleanli-
ness of antenna pattern). The '-F' option is similar to
the options -G, -P, -R, -S, -X (which specify weights
for gain, pattern cleanliness, input resistance, SWR
and input reactance). When using the -W option the
exact algorithm used to compute the fitness (and hence
the effect of this parameter) is best checked by look-
ing at the source code (see perform.c). This is one
area of constant program
improvement/changes/development, so its difficult to
say exactly the effect the parameter has. However,
increasing the weight of a parameter (using the -F, -G,
-R, -S or -X options) will make the associated parame-
ter have a greater effect on the fitness. However,
unless you optimise for a high FB ratio with the -W
option, then setting the -F option will have no effect.
For example, setting the options -F2.5 -W1 is a com-
plete waste of time. There you have used the -W1 option
to optimise only for gain (see -W option section of man
page) but have changed the weight of the FB ratio from
its default 1.0 to 2.5. If you are not optimising for
FB ratio, the weight you attach to it is irrelavent.
-<B>G</B><I>weight</I>_<I>gain</I>
is the floating point number (default 1.0) specifying
the weight to attach to the gain of the antenna when
using the '-W' option, which calculates a fitness for
the antenna based on one or more parameters (FB, gain,
input resistance, input reactance, SWR, cleanliness of
antenna pattern). The '-G' option is similar to the
options -F, -P, -R, -S, -X (which specify weights for
FB ratio, pattern cleanliness, input resistance, SWR
and input reactance). When using the -W option the
exact algorithm used to compute the fitness (and hence
the effect of this parameter) is best checked by look-
ing at the source code (see perform.c). This is one
area of constant program
improvement/changes/development, so its difficult to
say exactly the effect the parameter has. However,
increasing the weight of a parameter (using the -F, -G,
-R, -S or -X options) will make the associated parame-
ter have a greater effect on the fitness. However,
unless you optimise for gain with the -W option, then
setting the -G option will have no effect. For example,
setting the options -G2.5 -W2 is a complete waste of
time. There you have used the -W2 option to optimise
only for FB ratio (see -W option section of man page)
but have changed the weight of the gain from its
default 1.0 to 2.5. If you are not optimising for gain,
the weight you attach to it is irrelavent.
-<B>K</B><I>keep</I>_<I>for</I>_<I>tries</I>
<I>keep</I>_<I>for</I>_<I>tries</I> is the number of tries for the optimise
to persist using the original data file as the starting
point for optimisation. By default it is 1, which means
the program immediately looks from a new position once
a better one is found. It is theeoretically possible
that this might result in a quick, but poor local max-
imum. If however, <I>keep</I>_<I>for</I>_<I>tries</I> is 1000, it will stay
at a position for 1000 iterations after finding the
last best result, before considering this to be a glo-
bal optimum. Then it starts for the new position. In
practice, I have found this option to make matters
worst in most cases. It was added to avoid the local-
minimum problem, but it appears the optimisation sur-
face is pretty smooth, so it just slows the program,
without gaining much. Anyway, it can stay as an option,
but check the results with/without carefully before
using extensively.
-<B>P</B><I>pattern</I>_<I>cleanlyiness</I>
is the floating point number (default 1.0) specifying
the weight to attach to the cleanness of the antenna
pattern when using the '-W' option, which calculates a
fitness for the antenna based on one or more parameters
(FB, gain, input resistance, input reactance, SWR,
cleanliness of antenna pattern). The '-P' option is
similar to the options -F, -G, -R, -S, -X (which
specify weights for FB ratio, gain, input resistance,
SWR and input reactance). When using the -W option the
exact algorithm used to compute the fitness (and hence
the effect of this parameter) is best checked by look-
ing at the source code (see perform.c). This is one
area of constant program
improvement/changes/development, so its difficult to
say exactly the effect the parameter has. However,
increasing the weight of a parameter (using the -F, -G,
-R, -S or -X options) will make the associated parame-
ter have a greater effect on the fitness. However,
unless you optimise for a clean antenna pattern with
the -W option, then setting the -P option will have no
effect. For example, setting the options -P2.5 -W1 is a
complete waste of time. There you have used the -W1
option to optimise only for gain (see -W option section
of man page) but have changed the weight of the pattern
cleanliness from its default 1.0 to 2.5. If you are not
optimising for a clean radiation pattern, the weight
you attach to it is irrelavent. With appropiate use of
the -W option (eg -W49 for gain, SWR and a clean pat-
tern), the computer program finds the level of the most
significant sidelobe, wherever it may be outside the
main bean. It then optimises to reduce this. The -P
option tells it how much weight to put on reducing this
sidelobe.
-<B>R</B><I>weight</I>_<I>resistance</I>
is the floating point number (default 1.0) specifying
the weight to attach to the obtaining an input resis-
tance close to Zo on the antenna when using the '-W'
option, which calculates a fitness for the antenna
based on one or more parameters (FB, gain, input resis-
tance, input reactance, SWR, cleanliness of antenna
pattern). The '-R' option is similar to the options -F,
-G, -P, -S, -X (which specify weights for FB, gain,
pattern cleanliness, SWR and input reactance). When
using the -W option the exact algorithm used to compute
the fitness (and hence the effect of this parameter) is
best checked by looking at the source code (see
perform.c). This is one area of constant program
improvement/changes/development, so its difficult to
say exactly the effect the parameter has. However,
increasing the weight of a parameter (using the -F, -G,
-R, -S or -X options) will make the associated parame-
ter have a greater effect on the fitness. However,
unless you optimise for an an input resistance close to
Zo, with the -W option, then setting the -R option will
have no effect. For example, setting the options -R2.5
-W1 is a complete waste of time. There you have used
the -W1 option to optimise only for gain (see -W option
section of man page) but have changed the weight of the
resistance from its default 1.0 to 2.5. If you are not
optimising for an input resistance close to Zo, the
weight you attach to it is irrelavent.
-<B>S</B><I>weight</I>_<I>swr</I>
is the floating point number (default 1.0) specifying
the weight to attach to the SWR of the antenna when
using the '-W' option, which calculates a fitness for
the antenna based on one or more parameters (FB, gain,
input resistance, input reactance, SWR, cleanliness of
antenna pattern). The '-S' option is similar to the
options -F, -G, -P, -R, -X (which specify weights for
FB, gain, pattern cleanliness, input resistance and
input reactance). When using the -W option the exact
algorithm used to compute the fitness (and hence the
effect of this parameter) is best checked by looking at
the source code (see perform.c). This is one area of
constant program improvement/changes/development, so
its difficult to say exactly the effect the parameter
has. However, increasing the weight of a parameter
(using the -F, -G, -R, -S or -X options) will make the
associated parameter have a greater effect on the fit-
ness. However, unless you optimise for SWR with the -W
option, then setting the -S option will have no effect.
For example, setting the options -S2.5 -W1 is a com-
plete waste of time. There you have used the -W1 option
to optimise only for gain (see -W option section of man
page) but have changed the weight of the SWR from its
default 1.0 to 2.5. If you are not optimising for SWR,
the weight you attach to it is irrelavent.
-<B>T</B><I>position</I>_<I>tolerance</I>
<I>position</I>_<I>tolerance</I> is the standard deviation in mm of
the accuracy with which you can cut elements. Since
99.7% of elements will be with 3 standard deviations of
the correct position (stats theory says this), set -T2
if virtually all (well 99.7%) of elements are within
3x2=6 mm of the correct position.This option *must* be
used with the '-t' option and can't be used with any
other options apart from
-<B>W</B><I>Weighted</I>_<I>algorithm</I>
Try to get an antenna which is better according to a
weighted combination of parameters, rather than require
them all to improve. The integer specifies what to con-
sider in the weighted parameters.
W1 Gain.
W2 FB
W4 R
W8 X
W16 SWR
W32 SIDE_LOBE
You can logically AND these together, so for example
-W3 will optimise using a weighted combination of gain
and FB. -W49, will use a weighted combination of gain,
swr and sidelobe leve, since 32+16+1=49.
-<B>X</B><I>weight</I>_<I>reactance</I>
is the floating point number (default 1.0) specifying
the weight to attach to achieving a low input reactance
on the antenna when using the '-W' option, which calcu-
lates a fitness for the antenna based on one or more
parameters (FB, gain, input resistance, input reac-
tance, SWR, cleanliness of antenna pattern). The '-X'
option is similar to the options -F, G, -P, -R and -S
(which specify weights for FB ratio, gain, pattern
cleanliness, input resistance, and SWR). When using the
-W option the exact algorithm used to compute the fit-
ness (and hence the effect of this parameter) is best
checked by looking at the source code (see perform.c).
This is one area of constant program
improvement/changes/development, so its difficult to
say exactly the effect the parameter has. However,
increasing the weight of a parameter (using the -F, -G,
-R, -S or -X options) will make the associated parame-
ter have a greater effect on the fitness. However,
unless you optimise for a low input reactance with the
-W option, then setting the -X option will have no
effect. For example, setting the options -X2.5 -W1 is a
complete waste of time. There you have used the -W1
option to optimise only for gain (see -W option section
of man page) but have changed the weight of the reacti-
ance from its default 1.0 to 2.5. If you are not
optimising for a low input reactance, the weight you
attach to it is irrelavent.
-<B>Z</B><I>Zo</I>
<I>Zo</I> is the characteristic impedance used when evaluating
the VSWR, reflection coefficient and other similar cal-
culations. The optimiser usually tries to bring the
input impedance of the antenna to this value. It is set
by default to 50 Ohms, so the default is equivalent to
-<I>Z50</I> but may be set to any positive number. Set to 12.5
Ohms if you are going to feed the antenna with a 4:1
balun. Generally speaking, the gain of a Yagi can be
higher for low input impedances, but of course such
antennas are more difficult to feed.
<I>filename</I>
This is the name of the file containing the antenna
description. It is expected to be in a format created
by either <I>input</I> or <I>first</I> - two other programs in the
<I>Yagi</I>-<I>Uda</I> <I>project</I>. This is an ASCII text file.
<I>iterations</I>
is an integer specifying the number of iterations for
the optimiser to perform to try to get the best
antenna. Time will limit the number you choose. 1000
iterations of a 1ele yagi takes about 5 seconds, a 6ele
approximately 60 seconds, an 11 element 350 seconds, a
20 element 1030 seconds, a 33ele 2440 seconds, a 50ele-
ment 5400 seconds, 100ele 21320 seconds all on an old
25MHz 486 PC with no external cache. When using the -<I>A</I>
option the <I>iterations</I> is automatically set internally
so only one attempt is made. When using the '-t' and
'-T' options, <I>iterations</I> specifies the number of itera-
tions to attempt to get a poorer design, to check the
sensitivity of the design to small manufacturing toler-
ances.
</PRE>
<H2>EXAMPLES</H2><PRE>
Here are a number of examples of using <I>optimise</I>.
1) optimise 5ele 1000
Here the file 5ele will be optimised using the default sys-
tem for 1000 iterations. The default might typically require
gain, FB and SWR to all improve, but this may be changed at
any time. In any case, the program tells you what its
optimising for. By default the program will only optimise to
the selected parameters are good, not over-optimising any
one at the detrement of the others.
2) optimise -b30 -f50 -s2 5ele 1000
This is similar to above, but the boom can not extend by
more than 30% from its original length, FB ratios above 50
dB are considered acceptable, as are SWR's less than 2:1.
The optimised resultant antenna is likely to have better FB
ratio, but poorer SWR than in (1) above.
3) optimise -o1 5ele 1000
This will simply optimise 5ele for maximum forward gain. The
resultant antenna may have a poor FB ratio and is likely to
have an unacceptably low input impedance and hence high
VSWR. This is not a very sensible method of optimisation.
4) optimise -W49 -l7 5ele 10000
This will optimise the file 5ele using for 10000 iterations.
It will require that the weighted performance of the antenna
in three important parameters (gain, sidelobe level and SWR)
improves from one design to the next. One or two parameters
can actually get worst from one design to the next, but the
weighted performance is better. The positions of the ele-
ments or lengths of elements will not change by more than 7%
in each iteration.
5) optimise -g -S30 -G50 -F20 -p1500 5ele 10000
This will optimise the file 5ele using a genetic algorithm.
1500 antennas will be randomly designed. The performance of
each of these will measured using a 'fitness' function,
weighted 30% to SWR, 50% to gain and 20% to FB ratio. The
probability of breading from a pair of antennas is propor-
tional to the fitness function.
6) optimise -w atv_antenna 10000
This will optimise the file atv_antenna for a best average
performance over a wide band. The progrram calculates the
gain, FB and SWR at three frequencies, then computes an
average (mean) performance of the antenna over the band. N
iterations will take 3x as long to execute as N iterations
on the same antenna without the '-w' option.
7) optimise -t0.1 -T1 good_design 100
This will take the file good_design and make 100 different
antennas from it, to simulate the effects of building toler-
ances. Each element is assumed to be cut so that the mean
error of all elements is 0 mm, but a standard deviation of
0.1 mm, so 68.4% of element lengths are within 0.1 mm, 95.4%
within 0.2 mm and 99.7% with in 0.3 mm. The accuracy of
placing elements along the boom is much lower, so here we
have specified a standard deviation of 1.0 mm, so 68.6% of
elements are placed within 1 mm of the correct position,
95.4% within 2 mm of the correct position etc. The program
will report the *worst* performances achieved. If the per-
formance dips too mush, then you either need to build them
better, or get a design that's less critical!
</PRE>
<H2>STOPPING</H2><PRE>
<I>Optimise</I> will stop after the number of iterations specified
in the parameter <I>iterations</I>. It will also stop if a file
<I>stop</I> exits in the current directory of the executable
<I>optimise</I> This file can of course only be created using a
multi-tasking operating system such as Unix. It is *not*
advisable to stop the program by hitting the DEL key (Unix)
or CONTROL-C (DOS), as one of the files may be open at the
time, resulting in an empty file. Files are not open for any
longer than necessary (they are closed immediately after
writing to them), so this is not a likely occurrence, but
can still occur.
</PRE>
<H2>LIMITATIONS</H2><PRE>
I'm not aware of any limitations, apart from that filenames,
including full path, can't exceed 90 characters.
</PRE>
<H2>FILES</H2><PRE>
filename Antenna description, created by input or first.
filename.up Update file, listing achievements of optimise.
filename.bes Best file, containing the best design to date.
changes File that causes the program to pause to re-adjust weights.
stop File that stops optimisation process.
</PRE>
<H2>SEE ALSO</H2><PRE>
<B>first(1)</B>, <B>input(1)</B>, <B>output(1)</B>, <B>yagi(1)</B>, <B>first(5)</B>, <B>input(5)</B>
<B>output(5)</B> and <B>optimise(5)</B>.
</PRE>
<H2>PLATFORMS</H2><PRE>
Both DOS and Unix versions have been built. The DOS version
as distributed requires a 386 PC with a 387 maths coproces-
sor.
Although I have altered the source to make it more compati-
ble with DOS (reduced file name lengths etc), my wish is to
build a decent program, rather than fit the program to an
outdated operating system. If there is a *good* reason to
use code that is incompatible with DOS, this will be done.
Since <I>optimise</I> takes a while to optimise an antenna (I've
optimised one design for a week), it is obviously more sen-
sible to build this program under a multi-tasking operating
system, as otherwise a PC can be tied up for days.
</PRE>
<H2>BUGS</H2><PRE>
Bugs should be reported to <B>david.kirkby@onetel.net</B>. Bugs
tend actually to be fixed if they can be isolated, so it is
in your interest to report them in such a way that they can
be easily reproduced.
The program will dump core (crash) if asked to optimise a
1ele beam, without any arguments. This is because a 1ele
beam has no parasitic elements and by default the program
only changes parasitic elements.
Some of the options are not checked for sensible values,
although most are now checked and report if they are out of
range.
If the user specifies very large manufacturing errors using
the '-t' and '-T' options, its possible for elements to
overlap or for element lengths to become negative. This will
cause numerical errors. Any reasonable values will not cause
this.
On long Yagi's (50 elements) optimise can go a bit silly. It
can optimise say a 1296MHz Yagi to get 20 dB at 1296 MHz,
but less than 0 dB at only 1 MHz away. Needs some thought!
The level of the sidelobes is not computed with the GA or
some other optimisation types. This will be corrected later.
All those I don't know about.
</PRE>
<H2>AUTHORS</H2><PRE>
Dr. David Kirkby G8WRB (david.kirkby@onetel.net). with help
with converting to DOS from Dr. Joe Mack NA3T
(mack@fcrfv2.ncifcrf.gov)
</PRE>
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