[HCARC] Computer Programs

[Kerry Sandstrom]

John,

I think some of the software is made to appear intimidating!  I actually did 
a program on VOACAP for the club a couple years ago, but unfortunately I had 
some hard drive problems between then and now and lost it.

VOACAP is not very difficult. Most of the parameters never change.  Once you 
get the inputs set up for your station, you probably won't even notice them. 
VOACAP actually has several very useful features.  First, the is a list of a 
few thousand locations that includes lat and lon by degrees and minutes(Try 
to find that list any place else!).  One portion is by state and for Texas 
it includes Harper.  It is quite complete.  It has lists by continent also. 
Some of the lists are "interesting" such as a list of military 
installations, A DXCC list, an NCDXF list of beacons and a list of locations 
that ITU uses for propagation analyses!  It also has quite a few antenna 
models whose parameters can be adjusted and new antenna patterns plotted. 
I'll bring my laptop to the next few meetings and we can play during the 
pre-meeting time if you like.  Bring a "thumb drive" in case you would like 
some of the files.  After I did the VOACAP program at the meeting there 
wasn't much interest so I would hesitate to do another program on the 
subject.

I hope you realize that no propagation program does any good real-time. 
VOACAP is primarily useful to let you see what should be happening on a 
normal day.  If you see abnormal propagation you have a chance of 
recognizing it and going to a frequency and beam heading that will give you 
the best chance of finding something interesting.  The "big boys" that use 
VOACAP are mainly using it for frequency and station planning for 2-3 years 
in the future.  When I was in the real-time HF business with an OTH-B radar, 
we relied on ionospheric sounders as well as our own backscatter signal.  It 
is pretty clear that SW Broadcasters like Radio Moscow also used their own 
backscatter signal to adjust the elevation angle of their transmitting 
antennas.  I use VOACAP at work and I taught one of my coworkers to use it 
also.  He loves it.  I've tried to teach a couple others, but they just 
didn't have the interest.  Its really not difficult.

I haven't used or even seen ELNEC myself, however it does use NEC2 as the 
"engine".  The non-public domain part of ELNEC seems to be the GUI.  With 
4NEC2, you can either use the GUI to develop the antenna model graphically 
or you can use the original NEC2 input format.  That format is FORTRAN-style 
80 column cards.  No, I don't use cards, but the input screen appears like a 
80 column line of data and spaces.  I find it easier than the graphical 
input.  It is just what you get used to.  I think once you understand what 
is going on it will be easy.

I dont know about ELNEC, but 4NEC2 gives you several hundred antennas and 
the ability to change the parameter on those antennas to modify the design. 
Unless you're doing something weird, you may never have to enter an antenna 
from scratch.  Naturally I've had to deal with some weird antennas where I 
couldn't trust the existing data so I've had to mess with doing an antenna 
from scratch.

Digital copies of the original Lawrence Livermore National Lab documentation 
are available.  4NEC2 included some of the documentation in its files.  Talk 
about a software manual, it runs several volumes each over a hundred pages. 
I have digital copies of a couple of the volumes including the User's Manual 
which describes the input files in excruciating detail.  There are probably 
75 or so different card formats, but I only have had to use a dozen.  Yes, 
it goes out of its way to be intimidating!  The Users's Manual is only about 
500kb so if you need one soon, I can e-mail it to you.

In summary, its really not a big deal to run, it just takes a little time to 
get started.

Kerry