I started RF antenna modelling using various
versions of NEC, like EZNEC. You can play around with
simple wire structures and see what happens as you change
sizes, spacings and frequency. There are many free sources
of this software. It grew out of a DOS version to which a
number of people added Windows front-ends.
simulation, again free I believe, there is APPCAD, which
can be downloaded from
If you can get hold of a copy of Mathcad, then the
following site has a number of Mathcad routines for RF
design, including filter synthesis
Hope that helps.