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ANTPLOT.DOC
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1993-11-11
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ANTPLOT.
SIDE-TOWER MOUNTED ANTENNA
PATTERN PREDICTION PROGRAM VER. 5.3
By Ronald J. Jakubowski and Alex F. Dolgosh
Copyright 1992-93 The Antenna Specialists Co.
All Rights Reserved
Program No. 3 of the Antenna Specialists RF TOOLS Series
INSTALLATION:
The diskette supplied contains the files necessary to run the
ANTPLOT program. It may be run from the floppy, or may be copied
into a subdirectory on your hard disk drive (C:\ANTPLOT, for
example). To run the program, type ANTPLOT and press ENTER.
BACKGROUND:
For years, antenna manufacturers and consultants have known that
antennas mounted off the side of towers exhibit radiation patterns
which are affected by the tower structure acting as a complex
passive reflector. An "omnidirectional" antenna no longer creates
an omnidirectional field.
In 1969, the engineers at The Antenna Specialists Company mounted
a tower on a rotatable platform on their test range and measured
side-mounted antenna patterns by rotating the entire tower. As
more and more patterns were measured at different spacings on
towers with different face dimensions, it finally was concluded
that reasonable accuracy could only be obtained by modelling an
exact installation. The many variables prevented interpolating
results for an installation falling "between" two measured
patterns.
The work done in the 1969-1970 period was archived for possible
future reference.
As time progressed, computers integrated their way into all facets
of business. The need to provide more detailed systems information
grew, and the ability of systems engineers to perform was greatly
tested. Fifteen years after the test range data was archived, the
A/S Systems Engineering Department was tasked with the goal of
writing software to predict these patterns. The result is ANTPLOT
- a program which, when compared to the real data on file for over
two decades, will provide pattern predictions with reasonable
accuracy. Since many other variables can affect the patterns, use
of this data for system design is at your own risk.
SYSTEM REQUIREMENTS:
ANTPLOT will run on most IBM-compatible PCs.
A configuration utility will appear the first time the program is
run which allows ANTPLOT to be configured for output devices for
printing or plotting. It may be recalled from the opening screen
for changes.
The plotting routines are written in HP Graphics Language (HP GL)
and the program will drive either an HP 7475A desktop plotter or a
laser printer that is HP GL compatible, such as the HP LaserJet
IIIp. If a LaserJet IIIp is used, it should have 5 megabytes of
RAM memory, and the "Page Protection" item of the Configuration
Menu should be set to ON to allow complex graphics. See the HP
LaserJet IIIp Printer Getting Started Guide.
Memory usage is not intensive, so minimal 640K machines have no
problem with ANTPLOT.
Because the program draws screen displays and calculates patterns
point-by-point around the azimuth, a math coprocessor is highly
recommended for speedy execution of the graphic display.
PROGRAM OPERATION:
ANTPLOT is essentially user friendly to the Systems Engineer and
most potential users who have a knowledge of antennas and towers
adequate to interpret the pattern generated by the program.
ANTPLOT prompts the user for the input of several variables - tower
shape, geometry of mounting, operating frequency, face dimension of
tower, spacing of antenna from tower and azimuthal location of side
mount.
As an alternative to spacing, the user is prompted to enter 0
(zero) to receive a recommendation where near omnidirectionality is
desired. The program will then calculate the pattern for 0.5 ft.
increments out to 8 feet. A table of ratios of maximum to minimum
signal levels - compared to depth and location of greatest null -
will allow an experienced system designer to select a most
advantageous spacing, with a ratio of 1:1 being omnidirectional.
A pattern may be plotted for any set of variables to study each in
detail.
The menu bar at the bottom of the screen provides options for
output of data.
RFTOOL3A
October 14, 1993