Hacker Chronicles 2/HACKER2.BIN/290.MN.DOC

Text File | 1988-11-20 | 31KB | 620 lines

                 MN Antenna Analysis


    MN is an enhanced version of the classic MININEC antenna analysis
program for IBM-PC and compatible computers.  MN is much easier to use than
MININEC, and is oriented toward amateur radio.  No changes have been made to
the antenna modeling algorithm contained in MININEC Version 3 Change 11, as
released by the Naval Ocean Systems Center (except to fix a bug involving
Laplace Transform loads), but substantial changes have been made in the way the
program interacts with the user, and many new features have been added.

    This note is just intended to help you with aspects of the program that
are not readily apparent.  How to run the program is largely self-explanatory,
and can be learned by experimenting with the sample antenna files provided.


                New Features


    The most important new feature is a provision for antenna files.  This
allows the antenna characteristics to be captured from a text file instead of
from the keyboard, saving you the considerable trouble of reentering a
complicated antenna geometry by hand every time you start up the program.  It
permits you to interrupt your work, save it away, and come back to it later
when it is convenient, without having to start from scratch.  It also enables
you to build up your own library of designs, from which you can easily retrieve
and modify antennas for new applications.  You can use any text editor or word
processor to create the antenna file, as long as it comes out in ordinary ASCII
characters.  Commands are available for listing, loading, viewing, and editing
antenna files.

    If you have a graphics display card (CGA, EGA, or HGC) you can plot the
far-field azimuth and elevation patterns directly on your screen.  You may
create polar plots using the standard ARRL log dB plotting scale.  These
patterns may be directly compared with those in amateur antenna publications.
You may also plot in a linear dB scale so that small sidelobes are easier to
see.  Alternatively, the rectangular plot reveals all pattern detail uniformly.
The plots are saved automatically and can be viewed at a later time without
redoing the analysis.  For the EGA and HGC a comparison mode allows you to
switch screens instantly between the plots of two antennas without having to
wait while the plots are redrawn.  This provides a very revealing pattern
comparison.  You can make hardcopies of the screen plots on printers having
Epson-compatible dot graphics.

    A new command has been added to compute forward gain, front-to-back
ratio, maximum sidelobe level, beamwidth, and vertical angle of radiation.  You
no longer have to extract these antenna parameters manually by examining
tabulated directive pattern listings.

    The SWR is computed and displayed in two ways, revealing both the match
to a given feedline and the inherent bandwidth properties of the antenna.

    The maximum number of pulses has been increased from 50 to 126.  This
allows complex antenna systems to be modeled, including complete multiband
antenna installations in order to find interactions among separate antennas.

    You may specify the antenna dimensions in feet, inches, meters,
centimeters, or millimeters.  Wire diameter is used instead of radius, and you
may define this by specifying the wire gauge.  You may choose to have results
displayed in dBd or dBi.  Elevation angle (the angle with respect to the
horizon) is used instead of zenith angle (the angle with respect to overhead).
A single file containing a record of the data generated during the antenna
analysis is automatically created and given the same name as the antenna file,
with the extension .RUN.

    The all-capital-letters display style has been done away with, and
upper or lower case is accepted from the keyboard.  Defaults are provided for
all keyboard inputs and are indicated by [brackets].  Entering just a carriage
return selects the default value.


                 System Requirements


    MN.EXE requires an IBM-PC or compatible computer with at least 300K
bytes free memory.  You need at least 450K bytes if you invoke PLOT.EXE
directly from MN.EXE, but only 150K bytes when PLOT.EXE is executed by itself.
A Color Graphics Adapter, Enhanced Graphics Adapter, or Hercules Graphics Card
is required for plotting.  Both programs will run much faster if a math
coprocessor chip is installed, but one is not required.  A hard disk is not
necessary.  An editor or wordprocessor program is needed to create or modify
antenna files.  DOS 3.00 or later is recommended to avoid certain bugs in
earlier DOS versions which may impact MN.


                Antenna Files


    All characteristics of an antenna system, except for details concerning
the ground environment, are specified in an antenna file.  An antenna file must
have the extension ANT.  The antenna file can be specified as a command line
parameter when starting MN; otherwise you will be prompted for it.  Similarly,
when changing to another antenna using the A command, you may specify the new
filename as a command line parameter; otherwise you will be prompted for it.
In any case you need not enter the ANT extension, it will be supplied
automatically.  You may specify a drive and path ahead of the filename if
necessary.

    The format of an antenna file is illustrated below by a sample file for
a 3 element beam.  In actual antenna files no comments are permitted on the
lines containing antenna information, but they may be added freely at the end.


3 Element Yagi      {1 line title for the antenna}
Free Space      {Use any other character string for antennas over ground}
14.2 MHz      {"Hz", "KHz", or "GHz" may also be used}
3 wires, feet     {Also "inches", "meters", "centimeters", or "millimeters"}
10  -8,-17,0    -8,17,0   .125     {For each wire: # segments, XYZ coordinates
10  0,-16.5,0   0,16.5,0  1.5"              of each end, and diameter}
10  7,-16,0     7,16,0    1.5in  {All 3 wires are 1.5 inches in diam}
1 source      {Number of sources}
14,100,0      {Pulse number, voltage, phase of the first source}
0 loads          {Number of loads}


    Segments, sources, pulses, and loads will be explained in subsequent
sections.

    To increase readability any combination of spaces, commas, or tabs may
be used as separators.  Any combination of upper and lower case is valid.  The
words "wires", "source", and "loads" may be singular or plural.

    To use a different dimension unit for an individual length you may
suffix the number with one of the following:

            ft  '  in  "  m  cm  mm

Don't put a space between the numerical value and the unit abbreviation.

    You may also specify the wire diameter by entering the wire gauge, for
example, #12.  A wire table is built into the program for even-numbered
standard annealed bare copper wire gauges from AWG 0 through 30.  Odd gauge
numbers are converted to the next larger wire diameter.


                Coordinate System


    X and Y are in the horizontal plane and Z is height.  In MN, if +X is
North then +Y is West.  MN maintains the original MININEC azimuth angle
convention, which is counterclockwise and reversed from normal compass
bearings:  0 degrees azimuth angle is along the +X direction, and 90 degrees
azimuth is along the +Y direction.  +Z is up.  The forward horizon is at 0
degrees elevation angle, 90 degrees is overhead, and 180 degrees is the rear
horizon.  The 180 to 360 degree positive angles can also be referenced by -180
to 0 degree negative angles.  Unidirectional antennas are assumed to be aimed
in the +X direction by the subroutine that computes gain, F/B, max sidelobe
level, and beamwidth.  The Z coordinate can be set to 0 if only free space
modeling is performed.

    To gain a mental picture of the geometry involved, imagine facing a 3
element beam 5 feet off the ground which is aimed at you.  Assume that the
center of the driven element has been put at X=0, Y=0, Z=5.  The main lobe of
the beam points directly at you, in the +X direction.  The elements extend in
the -Y direction to your left, and in the +Y direction to your right.  The
director has a +X coordinate, while the reflector is in -X territory.  Positive
azimuth angle is to your right (counterclockwise when viewed from above), and
positive elevation angle is above your head.


              Wires, Segments, and Pulses


    A wire is always straight in MN.  A bent wire is modeled by connecting
two straight wires.  Two or more wires are considered connected when they share
the same XYZ coordinates at an endpoint, and current will be allowed to flow
between the wires as if they were soldered together.  For example, each loop of
a cubical quad antenna is described by four separate wires whose endpoints lie
at four points.  A 2 element quad is thus modeled by 8 wires in MN, even though
a real antenna would actually have only 2 wires strung around the spreaders.  A
Yagi element composed of tapered sections of telescoping tubing may be
accurately modeled by using several connected wires having different diameters.
Wires which cross or which terminate at midpoints of other wires are not
considered to be connected because connections are allowed only at wire ends.

    MN allows you to specify how many segments each wire is divided into
for analysis purposes.  Generally, the more segments used the higher the
accuracy, but the longer the analysis takes.  The number of segments required
depends on the geometry of the antenna being analyzed and the accuracy
required.  For example, 5-25 segments are generally used for dipole elements
and 15-100 for full-wave loop elements.  Many segments are required for
antennas having very closely-spaced wires, such as folded dipoles.  To be sure
that you are using enough segments you should always increase the number of
segments and try a new run to see if the results change significantly.  This is
very important.

    MN uses the segmentation to divide the current in the wire into
sections called pulses.  The current is uniform within each pulse, and the
pulses are centered on segment boundaries.  No pulses are placed at wire ends,
where the current is always zero, but a pulse is placed at every wire junction,
and overlaps onto all wires making up the junction.  The number of segments
(not pulses) for each wire is specified in the antenna file.  MN will allocate
pulses after unscrambling all the wire connections.  The number of wires is
limited to 50, the number of pulses to 126, and the number of segments to 176.


                Sources


    A source of energy (feedpoint) is permitted at any pulse.  You must
have the feed symmetry in mind when you divide the driven wires into segments.
In the Yagi example above, the driven element uses an even number of segments
(10).  This results in an odd number of pulses between the segments (9), and
thus a centrally located pulse at the feedpoint (pulse #14, including the 9
pulses in the reflector wire which was specified first).  Specifying an odd
number of segments for the driven element would result in an off-center
feedpoint.  The first time MN is run with a new antenna file, the .RUN output
file generated by MN should be examined to verify that the pulses have been
distributed and numbered the way you intended.  In fact, the easiest way to
figure out which pulse number to specify as the feed point is by making an
initial guess, loading the antenna file, quitting, and then examining the
antenna geometry section of the .RUN file to see how the pulses really were
allocated.

    If an antenna has only one source, and you are not interested in the
magnitude of the antenna currents, then the voltage can be any nonzero value
and the phase can be set to 0.  For two or more sources the relative magnitudes
and phases of the sources will directly influence the antenna characteristics.


                  Loads


    You may specify up to 50 lumped loads for an antenna.  Typical amateur
antennas using lumped loads are triband beams, trap dipoles and verticals, and
loaded dipoles and whips.  Loads are always located at pulses.  There are two
different load models, impedance loads and Laplace Transform loads.  An antenna
may not mix the two kinds.  Here is an example of an antenna using one
impedance load, where the load is a simple resistor:


ZL1ACW's Big Rhombic
35 feet up    {Since not "free space" this antenna will be modeled over ground}
24.94 MHz
4 wires, feet
25   -182.7 0 35      0 81.35 35   #12     {Wire gauge specified instead of diam}
25   0 81.35 35       182.7 0 35   #12
25   182.7 0 35       0 -81.35 35  #12
25   0 -81.35 35      -182.7 0 35  #12
1 source
100,200,0
1 load
Resistor      {For impedance loads use anything other than "Laplace Transform"}
50,740,0      {Pulse # of the load, load resistance, load reactance}


    Laplace Transform loads permit complex networks to be modeled, such as
tuned circuits.  A Laplace Transform is a special polynomial representation of
a lumped circuit.  Here is an example of an antenna using two Laplace Transform
loads:


W3DZZ Trap Dipole for 80 through 10 meters
Free space
14.150 MHz
4 wires, feet
10  0 -54 0   0 -32 0  #14
10  0 -32 0   0   0 0  #14
10  0   0 0   0  32 0  #14
10  0  32 0   0  54 0  #14
1 source
20,100,0
2 loads
Laplace Transform
10,2        {Pulse # of load, order of Laplace Transform}
0,1        {Numerator, denominator coefficents of s^0}
8.2,0        {    "           "          "       "  s^1}
0,4.92E-4    {    "           "          "       "  s^2}
30,2        {Second load ... }
0,1
8.2,0
0,4.92E-4    {Scientific notation is OK.  This is .000492}


    The traps for this antenna consist of 8.2uH in parallel with 60 pF.
The Laplace Transform for a parallel LC circuit is Ls/(1+LCs^2).  L should be
given in uH and C in uF, since the program works in MHz internally.  Textbooks
on circuit theory contain explanations of Laplace Transforms.


                    Ground


    For antennas modeled over ground the program will ask a series of
questions to establish the ground characteristics to be used for forming the
far-field directive pattern.  You can specify up to ten concentric ground zones
centered at the origin, each having its own dielectric constant, conductivity,
radius, and height.  This is very useful for modeling antennas on hilltops, in
swamps or marshes, or mounted on vessels above the water line.  The last ground
zone always extends to infinity.  When 0 is entered for the number of ground
zones the antenna will be modeled over a perfectly-conducting ground plane
extending to infinity.

    For antennas over real earth a radial ground screen may be specified.
If you specify a ground screen and one ground zone, the soil characteristics
are assumed to be uniform.  If you specify a ground screen and two or more
zones, the soil under the radials is zone 1, with zone 2 beginning where the
radials end.  This is useful when the soil under the radials has been
chemically treated to increase its conductivity, and thus exhibits different
characteristics than the earth beyond.  The effective impedance of the ground
screen is combined in parallel with that of the earth underneath it when
determining the ground reflection factor used to calculate the far-field
directive patterns.  The ground screen model is most accurate for dense ground
screens employing more than 100 radial wires, but you should still use it for
smaller screens in order to obtain the best overall accuracy.

    The height of the first ground zone is always 0.  The height of other
ground zones can be used to approximate elevation variations in local terrain.
If the height drops from one zone to the next, any diffraction from the cliff
edge thus formed is not modeled.  If the height increases, any blockage of
radiation from the wall formed is not modeled.  These are minor effects.

    The antenna need not be located at the center of the ground zones.  The
ground zones are concentric with the origin (X=Y=Z=0), but you may place the
antenna at any coordinates.  You might use this to model reflection from a
small lake near the antenna, for example, or to more accurately model a very
long longwire or Beverage antenna which traverses several types of ground.

    Caution needs to be exercised when modeling antennas over real earth.
MN uses the ground characteristics, including those of the ground screen, only
in determining the ground reflection factor for the far-field directive
patterns.  Perfectly-conducting earth is assumed when the element currents are
calculated.  This implies that neither direct nor induced ground current losses
will be accounted for.  For horizontal antennas at reasonable heights these
losses are negligible, but for vertical antennas fed against poor ground
systems they are not.  In the latter case the antenna gain calculated will be
too high and the impedance too low, and these numbers should be regarded as
upper and lower limits, respectively.  A resistive load may be inserted at the
feedpoint to approximate ground losses.

    The most suitable reference for an antenna modeled over real ground is
not a dipole in free space, but a dipole or monopole substituted for the test
antenna with all other parameters unchanged.  Earth reflection coefficients
vary greatly with polarization and frequency, as well as with dielectric
constant and conductivity, so the reference antenna should operate at the same
frequency, with the same polarization, and with the same ground model as the
antenna being investigated.  Expect to see negative gains at very low elevation
angles, using realistic earth characteristics, for antennas that exhibit gain
in free space.  In particular, vertical antennas have very little response at
elevation angles near 0 degrees unless they radiate over salt water.  The same
is true for horizontal antennas over all types of ground, unless they are very
high.

    Keep in mind that dBd refers to a dipole in free space, not to a dipole
in the same environment as the antenna being analyzed.  dBi is a somewhat more
natural reference than dBd when evaluating antennas over ground.

    It takes 2-3 times longer to analyze an antenna over ground as in free
space.  When optimizing an antenna it is quicker to do as many preliminary runs
in free space as possible, leaving the final optimization over ground for last.


                  Pattern Generation


    Azimuth and elevation patterns are generated to create the plot files
used by PLOT.  MN also searches these patterns to find the beamwidth and
maximum sidelobe level.  Normally, the azimuth and elevation patterns are only
generated for 0 to 180 degrees.  The pattern in the 0 to -180 degree half-plane
is assumed to be the same.  For antennas which do not possess mirror symmetry,
you can cause 360 degree patterns to be generated by using the parameter "360"
with the G command.  This feature can be used to find the true radiation
pattern of an asymmetrical wire antenna erected to take advantage of randomly
positioned tall trees, for example.  If the antenna is modeled over ground the
elevation data is always restricted to the half-plane above ground.

    For free space models an elevation angle of 0 degrees is used during
the azimuth search to obtain the on-axis azimuth response.  For antennas over
ground you will be prompted for the elevation angle.  This permits you to focus
on a wave angle of interest for a particular propagation path.

    The patterns are normally generated in 2 degree increments.  For some
antennas a smaller step size can produce better plots by resolving very sharp
peaks and nulls.  You can force the patterns to be generated in 1 degree steps
by adding the parameter "1" to the G command.  This can be used in combination
with the "360" parameter because MN just looks for "1" or "360" anywhere on the
G command line.  The time required to generate and search the patterns is
doubled when using 1 degree resolution or when generating 360 degree data, and
it is quadrupled when doing both.

    If an azimuth or elevation search finds its maximum gain at 0 degrees
(the normal case for unidirectional antennas aimed in the +X direction) then
the 3 dB beamwidth is computed.  The beamwidth is found by locating the angle
on the positive angular side where the pattern drops more than 3 dB,
interpolating with the previous point, and then doubling the resulting value.
The interpolation enables the beamwidth to be accurately computed (for
symmetrical main lobes) even when searching data with 2 degree resolution.  The
other side of the main lobe is not examined, even if a 360 degree pattern is
generated.

    If a sidelobe is found which is larger than the rear lobe then its
level and angle are displayed.  This is useful when optimizing the pattern of
an antenna.  It is easy to get carried away and lose sight of the overall
pattern when optimizing F/B, a measurement which describes the pattern at only
a single point in the rear plane.  You might achieve 45 dB F/B but still have a
sidelobe at 120 degrees that is only 20 dB down.  The sidelobe display will
alert you to this.  Only the first 180 degrees in each plane is searched for
sidelobes.

    If the main lobe is found at an azimuth angle other than 0 then no
azimuth beamwidth or sidelobe information is given.  Instead, the gain and
azimuth angle of the main lobe are displayed, along with the level 180 degrees
to the rear, and the subsequent elevation search takes place in this plane
instead of at 0 degrees azimuth.  This is useful for longwires and other
antennas with skewed radiation patterns.

    The radiation pattern used in all cases is the total pattern, which is
the RMS sum of the horizontal and vertical components.  This is realistic for
evaluating HF antenna performance on randomly polarized incoming skywave
signals.  It also facilitates the analysis of imperfect antennas.  For example,
cubical quads typically show only 20-30 dB front-to-side ratio due to
incidental vertically polarized radiation from the mostly out-of-phase sides of
the quad loops.  As another example, the performance of Beverage antennas can
be accurately modeled.  This antenna consists of a long low horizontal wire
which responds principally to vertically polarized signals.  The unintended
pickup of horizontally polarized fields will reduce directivity, but MN will
account for this.  Note that for linearly polarized antennas the magnitude
computed for orthogonal polarization terms is typically down more than 130 dB
in MN analysis, so that the use of both fields will not lead to inaccurate
results when the response at only one polarization is of interest.


                    SWR


    MN computes SWR in two ways.  The first computation finds the SWR in a
50 ohm feedline attached to the antenna feedpoint.  This SWR value is displayed
every analysis run and is useful for antennas intended for direct feed.  (See
the "DOS Environment Variables" section below to change the 50 ohm value.)  The
second SWR computation uses the antenna input impedance at one frequency,
rather than the feedline impedance, as the SWR reference impedance.  This SWR
computation is designed to reveal the inherent bandwidth characteristics of the
antenna.

    The second SWR value is displayed whenever you use the F command to
change frequency.  This value is based on a perfect match having been made to
the antenna at the first frequency analyzed after reading the antenna file.
The matching network is modeled as a series coil or capacitor followed by a
broadband transformer.  The coil or capacitor tunes out any residual reactance
in the antenna input impedance, and the transformer matches the resulting pure
resistance to the feedline impedance.

    The variation in this second SWR will give you an idea of the inherent
bandwidth properties of the antenna, independent of any particular narrowband
matching network.  The only frequency-dependent aspect of the modeled matching
network is the smooth change in coil or capacitor reactance with frequency.
(If you run the first analysis at the antenna resonant frequency this small
effect is eliminated altogether.)

    If the antenna has multiple sources the SWR is computed at the first
source only.


                Aborting Calculations


    Because some of the calculations can take a long time (particularly if
a math coprocessor chip is not used), a provision has been made for aborting
from various program loops by pressing the <Esc> key.  The order of calculation
is such that the most fundamental results are available first.  This allows you
to use the abort feature to terminate unwanted calculations, as well as to
escape from command mistakes.  For example, if you are only interested in
obtaining input impedance, SWR, gain, and F/B, you may hit <Esc> after these
are displayed to terminate the azimuth and elevation pattern generation.  The
pattern data is used to find the beamwidth and maximum sidelobe levels, and
also for any subsequent plotting.  If you abort but later reanalyze, without
changing any parameters, the program will display the results previously
calculated, and immediately return to the pattern generation.  This avoids
duplicating the calculations already performed.

    If it takes more than one minute to fill and factor the mutual
impedance matrix the program will beep when it is done to alert you that
results are ready.


                DOS Environment Space


    DOS provides a convenient way for you to specify configuration
information to MN and PLOT.  The DOS SET command places information into the
DOS Environment Space in memory, where it can be retrieved later by a program.
SET commands can be put into your AUTOEXEC.BAT file and they will be
automatically executed every time you boot the computer.

    You may see what is currently in the DOS Environment Space by typing
SET.  You may eliminate an individual parameter by typing SET [parameter]=.

    There are several SET parameters used by MN and PLOT:

1.  MN Editor

    Your favorite text editor or word processor may be invoked from within
MN to edit the current antenna file.  To set this up do the following:

            SET EDITOR=Editorname

where Editorname is the name of your editor (no .EXE or .COM needed).  Whenever
the E command is given to MN, the current antenna filename will be appended to
Editorname and the resulting DOS command will be executed.  You may specify a
drive and path ahead of Editorname.  After you exit the editor MN will reread
the antenna file.  All antenna parameters will be reset to those in the newly-
edited file, so any temporary changes made using the Change commands will be
lost.  The .RUN file is also overwritten each time the antenna file is read
back in.

2. Library Directories

    When you accumulate many antenna and plot files it is nice to have
separate directories for them, so that the current directory doesn't get so
cluttered up.  You might use the current directory for antenna experiments,
saving optimized antenna files and their plots elsewhere.  You can tell MN and
PLOT to automatically reference another directory with SET commands.  You may
specify a directory for an antenna library and another for a plot library.
These libraries are used only for loading files; when MN creates a plot file
(or a .RUN file) it always writes it to the current directory.

    If your antenna library is in the subdirectory ANTENNAS and your plot
library is in PLOTS then do the following:

            SET ANTLIB=ANTENNAS
            SET PLTLIB=PLOTS

    You may specify a drive and path for the directories if necessary.
When this library facility is used MN and PLOT will list available files both
in the current directory and in the appropriate library directory.  To specify
a file from the library directory you only need to enter the filename.

    MN and PLOT always search the current directory first.  If you need
to force the program to use the library (when the same filename appears in the
current directory) just specify the complete path and filename.

    If you are using a dual floppy disk system you can put your antenna
library and plot library on a second disk drive.  This will give you plenty of
working space on your main drive and still allow access to the library files.

3. Reference dB

    To cause MN and PLOT to display gain figures in dBi rather than dBd
do the following:

            SET DB=dBi

    You may use any combination of upper or lower case for the three dBi
letters.  Gains in dBd are referenced to the peak gain of a half-wave dipole in
free space.  This is common for amateur antennas and is the MN default.  Gains
in dBi are referenced to an isotropic antenna in free space, which is an
antenna that radiates equally in all directions.  A dipole has 2.15 dB gain
over an isotropic antenna, so MN converts from one gain reference to the other
by adding or subtracting 2.15 dB.

4.  Feedline Impedance

    The reference feedline impedance for the SWR computation can be changed
from the default 50 ohms by doing the following:

            SET Z=Feedline impedance

5.  Location of COMMAND.COM

    MN needs to have access to the DOS command interpreter COMMAND.COM in
order to list antenna files, call your editor, and call PLOT.  PLOT needs
COMMAND.COM to list plot files.  Normally the DOS Environment Space will
contain the location of COMMAND.COM.  If it doesn't then you should do the
following:

            SET COMSPEC=[Drive:\]COMMAND.COM

where Drive indicates the disk drive whose root directory contains COMMAND.COM
while MN is executing.  If you are using a single floppy disk system you must
copy COMMAND.COM from your DOS system disk onto the MN disk, or use a RAMDISK.


             Summary of SET Commands


    SET EDITOR=Editorname
    SET ANTLIB=Antenna library directory
    SET PLTLIB=Plot library directory
    SET DB=dBi
    SET Z=Feedline impedance
    SET COMSPEC=[Drive:\]COMMAND.COM


            Summary of MN Command Parameters


MN Command    Parameter            Function
----------      ---------               --------

    G           1        Force 1 degree resolution for azimuth and
                elevation patterns

    G          360        Force 360 degree coverage for azimuth and
                elevation patterns

    A        Filename    Specify a new antenna file without waiting
                for the listing of available files

    P        Filename    Create a plot file with a root name
                different from that of the antenna file


                Additional Information


    NOSC Technical Document 938 contains a detailed description of the
original MININEC program, including mathematical formulation of the analysis
algorithm, model validation against empirical data, error analysis, and BASIC
program listing.  This 100+ page manual is available from the U.S. government
for $22.95.  It may be ordered by mail with a check, or by phone with a credit
card.  Request NTIS document number ADA181682 from:

            U.S. Dept. of Commerce
            National Technical Information Service
            5285 Port Royal Rd.
            Springfield, VA  22161
            [phone]