Antenna Modeling Software
NEC2 3-dimensional pattern for the KK1D Dipole on 17 meters.
Antenna modeling software is handy for designing new antennas and documenting as-built antennas. There are numerous free and proprietary programs available for the task. Most are based on the well documented Numerical Electromagnetics Code (NEC) or MiniNEC algorithms.
The main HF antenna at my location is a 125 foot (38 meter) dipole at a height of 10 meters fed with ladder line. The antenna is oriented North-South to within +/- 5 degrees or so. It works out pretty well, it has more gain than a dipole towards Europe and some other DX locations. It has come down during the last two hurricanes (Irene, Sandy), but is easy to restring with my trusty slingshot.
I found it handy to work up the antenna patterns in Arie Voors' 4nec2, then plot them "sandwiched" with an azimuthal equidistant chart centered on the QTH. Gabriel Rivat's (F6DQM) AziWorld software is used to create the maps, and the GIMP is used to sandwich the NEC2 and Aziworld images.
NEC will do a lot more, like compute impedances, SWR, Smith Charts, and even geographic coverage diagrams for specific times and ionospheric conditions. Here are some links to many NEC variants.
Another good antenna modeling program is MMANA-GAL, which is based on MININEC-3 algorithms.
MMANA-GAL patterns for the 36m dipole on 15 meters