NEC4WIN95VM is the Virtual
Memory version of NEC4WIN95. The user interface is the same as in
NEC4WIN95 with many additional features:
- Virtual
Memory allows a number of wires and segments limited only by physical memory and
free space on disk
- 3D interactive
display of Near Field data.
- Smith Chart
impedance output on Frequency Range.
- Loop Correction
for more accurate simulation of loops and Quads (also in
NEC4WIN95).
- ICEPAC File 13 generated
by NEC4WIN95VM can be used with powerful ICEPAC (IONCAP or
VOACAP) Propagation Analysis software.
More on Advanced features
What is Virtual
Memory?
Virtual
memory is a mechanism by which the hard disk is used as a transparent external memory
system. When real RAM is not sufficient, blocks of memory are
swapped to the disk to create more space in physical RAM.
NEC4WIN95VM
resolution time for a specific model is not growing in direct proportion to the number of
segments, but as a power 3 of that number.
For an N segments model, computation time
is on the order of N^3 (N power 3). This means that
If Project 1 with N segments takes 1 minute
to compute impedance
Project 2 with 2N (twice) will take (2*N)^2
or 4 minutes
Project 3 with 3N segments will take 3^3 or
... 27 minutes.
Who needs NEC4WIN95VM?
Anybody who simulates large models
with more than 50 wires and/or 250 segments which are the limitations imposed by Mininec
on NEC4WIN95.
50+ wire models are easy to reach with
multi-element beams using tapered tubes, loops and quads, multi antennas systems,
helicoidal antennas etc...
How many wires or segments can I use
with NEC4WIN95VM?
This depends on how much physical
RAM you have and if you have enough free space on disk to swap that
memory out. The main matrix used by the program must fit in physical
memory and can't be split. Look at the projects below and you will see can you can indeed have huge
projects. But don't forget that these projects take hours if not
days to simulate.
NEC4WIN95VM Limitations
The engine is still based on Mininec
and it has the same limitations as the non VM version. Close parallel wires, horizontal wires too close to the ground, sharp
corners may be a problem to simulate. Log Periodics and Transmission
Lines can't be simulated accurately with it. Antenna impedance is always calculated based on
Perfect Ground.
NEC4WIN95VM Projects Gallery
NEC4WIN95VM is currently used by a number
of professionals and amateurs working on large antenna systems. Take a look at
the monster project at the bottom of the page. This monster is a
system from Broadcast Partners in The Netherlands (www.CBT.nl)
and is used to transmit FM
on the tallest antenna in Europe (bigger than Eiffel tower). This will give you an idea of NEC4WIN95VM
capacity to handle large projects.
Loop for 232Mhz with grid reflector by Guenter Koellner, DL4MEA
QFH by G0HPO
and this monster ...
Limitations
Some MININEC3 limitations still
apply. Close parallel wires and wires close to the ground do not simulate well. Sharp
corners need segment tapering except in looped antennas. Impedance calculation assumes a perfect ground.
| Limitation |
Standard version |
Virtual Memory version |
MAXIMUM
NUMBER OF PULSES
MAXIMUM NUMBER OF SEGMENTS
MAXIMUM NUMBER OF WIRES
MAXIMUM NUMBER OF SEGMENTS PER WIRE
MAXIMUM NUMBER OF SOURCES
MAXIMUM NUMBER OF LOADS
MAXIMUM WIRE LENGTH IN ANY UNIT |
250
250
50
50
10
20
10000 |
*
*
*
50
100
100
10000 |
* Limited only by
maximum physical memory and hard disk space to swap all memory to
disk.
