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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. |
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EZNEC Antenna 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 designer. |
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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 recommended. |
 
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Microsoft OneNote 2010
One of the most useful programs to come along for a long
time, OneNote is the computer version of the three-ring notebook. Full of all
kinds of great features, like being able to cut and paste text and images directly from web
pages right into your notebook pages (and it even adds the URL so you know where
it came from), you'll wonder how you ever got along without it. |