Useful software for electronic design and simulation, and for everyday use--and it's all free.
LTspice IV Circuit Design and Simulation Software - Free
Although there's no substitute for actually building circuits, simulation
software can help you to lay out schematic diagrams, and design, and test with
speed and ease.
Included in this download are over 200 op-amp models, as well as resistors,
transistors, and other components, and it's all free. Highly recommended.
Design and Simulation Software -- Free Version
This is the full EZNEC antenna design and simulation program with all of the
features and a complete on-line manual. The only difference between this free
version and the standard programs is that this version allows only 20 antenna
segments, which limits the complexity of antenna you can analyze.
Even with the 20 segment limit, however, the demo program does a very
respectable job of analyzing a two-element quad, two- and four-element phased
vertical arrays, a simple Yagi, a W8JK, and many other antennas -- including
ones you create from scratch. You'll find this program interesting and
educational, and you'll get many useful tips about antennas and modeling from
the extensive on-line manual. Give it a try. It has no time limit or other
restrictions, and it's free!
You can read about antenna modeling software's capabilities and limitations in
MININEC: The Other Edge of the Sword, a great article written by the
FreeMind Mind Mapping Software -- Free
FreeMind mind mapping software is as fun and interesting to use as it is useful.
Much better than doodling ideas on the back of an envelope. Highly