PLOT PROGRAM
Copyright 1993 by Brian Beezley, K6STI
All Rights Reserved
PLOT Program..................................1
Running PLOT..................................1
Polar Plots...................................2
Rectangular Plots.............................2
Overlaying Plots..............................3
Comparing Plots...............................3
Pattern Synthesis.............................3
Screen Colors.................................3
Printing The Screen...........................4
Graphics Image Files..........................4
DOS Environment...............................4
Plot File Format..............................8
Index.........................................10
---- PLOT PROGRAM ----------------------------------------------
PLOT.EXE displays and prints far-field antenna radiation
patterns. Patterns can be generated by the MN Antenna Analysis
program, the AO Antenna Optimizer, the YO Yagi Optimizer, or
NEC/Yagis. Patterns can be plotted in polar or rectangular
coordinates. PLOT requires a 386+387 or 486DX and VGA.
PLOT can synthesize the gain and pattern for an array of
antennas from the pattern of a single antenna. This feature can
be used to investigate the performance of large EME arrays
without having to do a method-of-moments analysis of the entire
array.
---- RUNNING PLOT ----------------------------------------------
The quickest way to start PLOT is to give the name of a
plot file on the command line, for example, PLOT DIPOLE. If you
don't know which file you want, just type PLOT and plot files in
the current directory will be listed.
Select a file by moving the lightbar with the arrow
keys, PgUp, PgDn, Home, or End. Press Enter to select the
highlighted file. Alternatively, you may type a filename. As
you type, the lightbar moves to the first filename which matches
the characters entered. Press Enter whenever the desired file
is highlighted.
Select the last item ("Other") to enter a file or
directory name not listed. If you enter a directory containing
plot files, PLOT lists them and you may select one. See the DOS
Environment section for information on organizing plot files
into subdirectories.
PLOT normally begins by drawing a polar plot of the
azimuth/E-plane pattern using the log-dB scale. You may start
PLOT in other modes by supplying up to three option letters
after the filename as follows:
E Elevation/H-plane pattern
R Rectangular plot
L Linear-dB scale
For example, PLOT DIPOLE ERL will cause PLOT to draw the
elevation/H-plane pattern in rectangular coordinates. If a
polar plot is later selected, it will use the linear-dB scale.
These options may be entered at Other or on the command line.
Press F1 or any other nonfunctional key for help. The
help panel is context-sensitive; keys which aren't currently
functional are grayed-out. For example, the X and Y keys aren't
highlighted in polar mode.
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---- POLAR PLOTS -----------------------------------------------
Select polar plots with the P key. Either of two radial
scales may be used. The standard ARRL log-dB scale causes
lower-level sidelobes to be compressed toward the center of the
pattern. This emphasizes the shape of the major lobe. The ARRL
log-dB scale is widely used in amateur publications. It
provides a convenient way to compare the patterns of antennas
you develop to those of existing designs. It also produces
patterns having familiar shapes. The center of the plot is
minus infinity dB (no signal) with this scale, but there is
little plot area below -40 dB.
The other polar scale uses linear-dB. This scale cuts
off at -50 dB at the center of the plot. This scale provides
much more area between -20 and -50 dB than the log-dB scale. It
is useful for examining low-level sidelobes which may be hard to
see in a log-dB plot.
The dots forming the radial lines (the ones which are
not multiples of 30 degrees) are spaced every 2 dB. The dots
forming the circles are spaced at multiples of 1 degree. These
calibrations allow directivity values to be read from plots with
good accuracy.
When the antenna is in free space, PLOT draws a 360-
degree elevation polar plot. When over ground, only the upper
180-degree hemisphere is shown.
The polar plots are perfectly circular on monitors with
standard 4:3 aspect ratio. If the plots appear elliptical,
adjust your monitor's vertical height control.
---- RECTANGULAR PLOTS -----------------------------------------
You can change to rectangular (X-Y) plots with the P
key. This coordinate system can reveal small sidelobe detail
even better than the linear-dB polar plot, but the overall
pattern shape is not quite as apparent. The X-axis is azimuth
or elevation angle, and the Y-axis is the antenna response in dB
using a linear scale. The Y-axis cutoff (lower limit in dB) may
be changed using the Y key. This parameter is always a negative
number, but you may enter it without a minus sign for
convenience. The Y-axis cutoff is constrained between -1 and
-100 dB. The Y-axis is easiest to interpret when the cutoff
value is a multiple of 10 degrees, but you may enter any value
and the scale and grid will be drawn correctly. The X-axis
cutoff may be changed using the X key. You may enter any value,
but it will be rounded to the nearest multiple of 10 degrees
within the range of 10 to 180 degrees.
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---- OVERLAYING PLOTS ------------------------------------------
The O key lets you overlay a second pattern. Traces and
annotations for the patterns use different colors. Filenames
replace plot titles in the screen annotation.
---- COMPARING PLOTS -------------------------------------------
The C key selects a second plot file for pattern
comparison. The second plot is drawn into a separate screen
buffer. The buffers may be switched instantly with the
spacebar. This permits a precise, instantaneous, pattern
comparison which can reveal differences obscured by screen
clutter in overlay mode.
---- PATTERN SYNTHESIS -----------------------------------------
PLOT can synthesize the pattern and calculate the gain
for an m by n rectangular array of antennas given the pattern of
a single antenna. Since m and n can have any value and the
synthesis is very fast, you can quickly investigate the
properties of very large arrays.
Press the + key to add an antenna to the current array.
The antenna is added in the plane you're viewing. Press the -
key to remove an antenna.
Vary array spacing with the up/down arrow keys. Use the
Home and End keys for finer resolution and PgUp and PgDn for
coarser. Array spacing varies in the plane you're viewing.
Spacing can be different in the two planes, but all antennas are
spaced uniformly within a plane. PLOT uses wavelength units by
default. Press the U key to change to inches or millimeters.
You can compare the pattern of a synthesized array with
another pattern, but you can't normalize patterns or overlay
them. You can synthesize free-space patterns only.
PLOT ignores mutual impedances between individual
antennas when calculating array patterns. This interaction
usually is small for most antennas at the spacings typical of
stacked arrays. PLOT uses pattern integration to estimate array
gain. Calculated gain is generally within a few tenths of a dB
of true array gain. By varying array spacing and watching the
gain figure and pattern sidelobes, you can quickly determine the
best spacing for a desired gain/pattern trade-off.
---- SCREEN COLORS ---------------------------------------------
F5 changes screen colors. You can change colors for the
file-list screen and for the pattern screen. Use the left/right
arrows to select a screen item. Then use the Home/End, up/down
arrows, and PgUp/PgDn to cycle through 64 intensities for each
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of the red, green, and blue color components. This yields 256K
color choices. After selecting colors, save them by pressing S.
This writes color codes to the PLOT.INI file. PLOT reads
PLOT.INI whenever it begins execution and sets the colors
accordingly. If PLOT.INI is not present, PLOT uses a default
color set (simply delete PLOT.INI to return to the default color
set).
---- PRINTING THE SCREEN ---------------------------------------
PLOT prints text and graphics screens to HP LaserJet/
DeskJet printers and to Epson-compatible, dot-matrix printers.
Press F10 to print any screen. See the DOS Environment section
for details on configuring PLOT for your particular printer.
Unless you're in LaserJet landscape mode, PLOT does not eject
the page after printing a screen. This lets you print two
screens on one page.
The PSPLOT utility generates gorgeous plots on
PostScript printers from plot files. PSPLOT can overlay
patterns and can do multiple plots per page. PSPLOT is
available for $25 from Paul Terwilliger, NX1H, 11 North Shore
Rd., Chester, NH 03036, (603) 887-4346.
---- GRAPHICS IMAGE FILES --------------------------------------
PLOT can save the image of any graphics screen in the
.PCX file format. This feature lets you add PLOT graphics to
desktop-publishing and word-processing documents. If your
computer has a fax/modem, you can fax PLOT images.
Press F9 to generate a .PCX file. The output filename
is the antenna filename with the extension .PCX. Whenever you
press F9 again, an incrementing digit is appended to the
filename and another file is created. You can control image
size and centering with a DOS SET command. See the next section
for details.
---- DOS ENVIRONMENT -------------------------------------------
DOS provides a convenient way to specify configuration
information to PLOT. The DOS SET command places information
into the DOS Environment in memory where it can be retrieved
later by a program. SET commands placed in your AUTOEXEC.BAT
file will be executed automatically every time the computer
boots.
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You may view the DOS Environment by typing the
following:
SET
You may eliminate a SET parameter P by typing this:
SET P=
It's possible to run out of Environment space. To
enlarge it to 512 bytes, put a line similar to this one in your
CONFIG.SYS file:
SHELL=\COMMAND.COM /E:512 /P
There are several SET parameters used by PLOT. The
parameters may be entered in upper or lower case. Don't put a
space before or after the equal sign in SET commands.
1. Subdirectories
Once you accumulate many plot files, it's nice to
organize them into subdirectories. You might use the current
directory for antenna experiments, saving optimized plots
elsewhere. You can tell PLOT to automatically reference certain
subdirectories with a SET command.
Define subdirectories like this:
SET PLT=. PLOTS1 PLOTS2 PLOTS3
The period represents the current directory. It may
appear anywhere (or nowhere) in the list. You may define as
many subdirectories as you like. You can organize
subdirectories by antenna type, frequency range, designer, etc.
Without a SET command, the subdirectory list consists of
just the current directory.
PLOT begins by listing files in the first subdirectory
on the list. Subdirectory names are listed after the files.
Select a subdirectory to list its files.
You may specify a plot file from one of the
subdirectories on the PLOT command line without typing the path.
PLOT searches the subdirectories in the order given in the
subdirectory list.
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You may specify any subdirectory (not necessarily from
the list) on the command line and PLOT will list its plot files.
2. Gain Reference
To display gains in dBi rather than dBd, do this:
SET DB=dBi
3. Printer Type
To print graphics screens on many 9-pin, dot-matrix
printers, no SET command is required. However, some printers do
not recognize the special line-spacing command PLOT uses to
print an exact screen image. If your 9-pin printer won't print
PLOT graphics, try the following:
SET PINS=9ALT
For a 24-pin, dot-matrix printer, use:
SET PINS=24
For an HP LaserJet or DeskJet printer, use:
SET PINS=HPLJ
To try a landscape plot (not available on all laser
printers), use:
SET PINS=HPLJ L
For a bigger landscape plot, use:
SET PINS=HPLJ LB
PLOT normally draws LaserJet/DeskJet plots with a
border. To eliminate the border, add an X like this:
SET PINS=HPLJ X or LX or LBX
4. Printer Port
Graphics screens print on LPT1 by default. To print
graphics on another port, use one of the following:
SET LPT=LPT2
SET LPT=LPT3
5. .PCX Output
By default, AO generates .PCX screen images with 640 by
480 pixels. These images can be directly incorporated in
documents. However, the images won't be centered on fax pages
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because they have no margins. You can add margins with the
following command:
SET PCX=left top bottom
The three numbers specify margin size in inches. The
bottom margin is optional. You can use it to pad the image to
form a complete page if your fax software doesn't do this
automatically. Try left = .8 and top = 2.35.
You can create a double-size .PCX image by adding the
keyword BIG to the line (use upper or lower case). BIG is for
high-resolution fax mode.
6. Display Typeface
You can use the standard serif typeface built into your
VGA card with the following:
SET TYPEFACE=Serif
7. VGA Compatibility
PLOT can use a dual-paging scheme to provide smoother
graphics by fully buffering all screen changes. This scheme
requires a compatible VGA card with 512K video memory. If your
card is incompatible or has less memory, you'll get extraneous
graphics images. Dual paging eliminates the blink when you
change to a new screen. To try it, do the following:
SET PAGES=2
PLOT programs the VGA overscan register to extend the
background color into the overscan region surrounding the active
screen. This improves the appearance of text at screen edges.
However, some VGA cards generate the wrong overscan color,
yielding a distinct, off-color border. To fix this problem, try
the following:
SET OVERSCAN=FIX
8. Screen Bounce
When switched from graphics to text mode, the screens of
many monitors bounce or break up during resynchronization. PLOT
can blank the screen for a short period while the monitor
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settles. To try this, specify a short delay (like 0.1) in
seconds as follows:
SET BOUNCE=Delay
---- PLOT FILE FORMAT ------------------------------------------
If you have an output device not supported by PLOT (such
as a pen plotter), a program may be written to read a plot file
and drive the device directly. Here's a sample plot file with
comments in brackets:
W2PV 4-element 12-meter Beam {Title}
Free Space {Ground description}
24.900 {Frequency, MHz}
0 {Elevation angle, degrees}
1025 {Abs level in dBi*100 of largest azimuth data point}
91 {Number of azimuth points in the following data block}
0 2 6 14 25 40 58 79 104 132 163 199 ...
712 794 883 97810811190130814351571171618722038 ... {20 points
358337503969429248699999480041553767348832713096 ... per line}
238223572341233123302335234823692397243524812538 ...
40384513468742813938370535453434336133193306-2 {Field code}
0 {Azimuth angle, degrees}
1025 {Abs level in dBi*100 of largest elevation data point}
91 {Number of elevation points in the following data block}
0 1 3 8 14 22 32 44 58 74 92 112 ...
409 457 510 566 627 693 764 841 923101111051205 ... {20 points
175917181671162415821544151214871468145514471445 ... per line}
161516521693173717861838189519572024209821782266 ...
39664455464242463912368835333427335833193306
Each data point consists of four digits. Data values
are relative to the maximum data point in units of dB*100 down
from maximum. The points are ordered from the smallest angle to
the largest.
The number of points must be one of the following:
Angular Resolution Angular Span Number of Points
2 deg 0-180 deg 91
1 0-180 181
2 0-358 180
1 0-359 360
PLOT uses the number of points to determine the angular
resolution and angular span of the plot.
When a plot file is generated by MN or AO, the last data
point in the azimuth data block is followed by a numerical code.
The code identifies the electromagnetic-field component used to
generate the plot data. When a nonzero code is present, PLOT
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annotates the plot with the field component. Here are the
codes:
Field Code Component
0 Total
1 Horizontal
-1 Vertical
2 Right-Circular
-2 Left-Circular
3 Maximum-Linear
-3 Minimum-Linear
4 Axial Ratio
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INDEX
+ key 3
- key 3
.PCX file 4
24-pin 6
64 intensities 3
9-pin 6
Angular resolution 8
Angular span 8
Annotate 8
Annotations 3
AO Antenna Optimizer 1
Array 1, 3
ARRL log-dB scale 2
Arrow keys 1, 3
Aspect ratio 2
AUTOEXEC.BAT 4
BIG 7
Blink 7
Boot 4
Border 6
Calibrations 2
Circles 2
Color 3
Color codes 4
Command line 1
Comparing Plots 3
CONFIG.SYS 5
Current directory 1, 5
Data point 8
DBd 6
DBi 6
Default 3
Default color set 4
DeskJet 4, 6
Directivity values 2
Display Typeface 7
DOS Environment 4
Dot-matrix printers 4, 6
Dots 2
Dual-paging scheme 7
Eject 4
Electromagnetic-field component 8
Elliptical 2
EME 1
End 1, 3
Enter 1
Epson-compatible 4
10
Estimate array gain 3
Extraneous graphics images 7
F10 4
F5 3
F9 4
Fax 4
Free space 2
Gain 3
Gain Reference 6
Gain/pattern trade-off 3
Graphics Image Files 4
Graphics screens 6
Help panel 1
Hemisphere 2
Highlight 1
Home 1, 3
HP LaserJet 4, 6
Inches 3
Landscape plot 6
Lightbar 1
Linear-dB 2
Linear-dB scale 1
List 1
Log-dB scale 1
Lower-level sidelobes 2
LPT 6
Major lobe 2
Millimeters 3
MN Antenna Analysis 1
Mutual impedance 3
NEC/Yagis 1
Normalize 3
NX1H 4
Option letters 1
Other 1
Output device 8
Over ground 2
Overlay 3
Overlaying Plots 3
Path 5
Pattern comparison 3
Pattern integration 3
Pattern Synthesis 3
PCX file 4
PCX Output 6
Pen plotter 8
PgDn 1, 3
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PgUp 1, 3
Plane 3
Plot File Format 8
PLOT.INI 4
Polar Plots 2
PostScript 4
Print 4
Print graphics 6
Printer Port 6
Printer Type 6
Printing The Screen 4
PSPLOT 4
Quickest way to start PLOT 1
Radial lines 2
Radial scales 2
Rectangular array 3
Rectangular coordinates 1
Rectangular Plots 2
Resolution 3
Rounded 2
Run out of Environment space 5
Running PLOT 1
Sample plot file 8
Save 4
Screen Bounce 7
Screen buffer 3
Screen clutter 3
Screen Colors 3
Select a file 1
Serif typeface 7
SET BOUNCE 8
SET command 4
SET DB 6
SET LPT 6
SET OVERSCAN 7
SET PAGES 7
SET PINS 6
SET PLT 5
SET TYPEFACE 7
SHELL 5
Sidelobe detail 2
Smoother graphics 7
Spacebar 3
Subdirectories 5
Synthesize 1, 3
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Terwilliger 4
Traces 3
True array gain 3
U key 3
Vertical height control 2
VGA Compatibility 7
Video memory 7
Wavelength 3
X-axis 2
X-axis cutoff 2
Y-axis 2
Y-axis cutoff 2
YO Yagi Optimizer 1
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