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QRZ! Ham Radio 6
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QRZ Ham Radio Callsign Database - Volume 6.iso
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nec81inf.txt
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1994-11-27
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The modified source codes of NEC-81 antenna analysis program are located in
this directory.
The Sun-4 Fortran 77 compiler can read this code and the code works in
Sparc-based SUN-4 computers. Some f77 compilers (e.g. Stardent) do not
accept this code, though.
The compiling process is performed as follows (under UNIX OS):
f77 -0 nec3000 *.f >& errors
which makes an executable file nec3000 and directs the compiler messages to
the file named errors.
The array dimensions in the source code are modified to allow the maximum
number of segments to be 3000. The altered variables are listed below:
Variable Original Altered Purpose
name value value
------------------------------------------------------------------------
LD 300 3000 Max. number of segments
and surface patches
IRESRV 8100 1000000 Nr. of words in core
storage
NETMX 30 100 Max. number of non-
NDIMN 30 100 radiating neworks.
NDIMNP 31 101 NETMX, NDIMN and NDIMNP
must all be specified
NSMAX 30 50 Max. nr. of voltage sources
LOADMX 30 100 Max. number of loads
(LD Cards)
The program executes reasonably fast, if the simulation fits in the CPU
memory. If the machine has to use disk as a virtual memory, the execution
time grows rapidly. The core size is about 20 Mb, when the listed variable
values are used.
The core can be made smaller by reducing the value of IRESRV. The program
then makes temporary files on the disk, if the simulation does not fit in
the core.
nec_bat is a shellscript-file, which reads the names of the input- and
outputfiles from the file necfiles and writes the start- and endtimes of
the execution to the file dates. The program messages are directed to the
file nec_run_log. The purpose of the batch file is to allow running NEC on
background. nec_bat should be used as follows:
nec_bat &
which starts the process and leaves it running on background. Of course,
the NEC program can be used interactively as well, by typing the compiled
program name (e.g. nec3000) at the command line, in which case the program
prompts for the input- and outputfilenames and continues running on
foreground.
The results of the program have been compared to the results of the PC
version and they seemed to match. Only small differences in 3rd and 4th
decimal of the computed gains were noted. The execution time was about 1/10
of the PC version when computing a 250-segment simulation.
This is the first modified version, any comments and suggestions are welcome.
Petri Kotilainen OH3MCK