Dave writes:

Since you clearly know more about this stuff than me, do you know of
the best freely available software for this which works under Unix? (I
use Sun's Solaris for 99% of the things I do, including sending this
message. I use Solaris on my laptop too, rather than Windows).

Hence I'm almost certainly looking for source code in either C, C++ or
Fortran. Anything that works under Linux would almost certainly be
able to be compiled for Solaris without too much effort.
I found this page:

NEC-2 can be built for Linux, and binaries are available for some
distributions. I am sure NEC-4 also can, if you get a license.

However, I have seen strange results come out of NEC-2 on Debian
Linux. Looked like numerical instability, and could be caused by a
problem in the toolchain. I don't think these binaries are used much,
so they don't receive the amount of tender loving care that they
deserve.

73
LA4RT Jon, Trondheim, Norway