An expression calculator and unit converter which allows you to directly enter an expression to be evaluated. It is a handy and nice skinnable replacement for the standard Windows calculator with many additional features.
http://www.romanlab.com/1stcalc/
This calculator is designed to give the vertical length (height) of a particular antenna, for the frequency and wavelength chosen.
http://www.csgnetwork.com/antennaevcalc.html
Visualizing what a standing wave looks like is always difficult. Type in any reflection coefficient, VSWR, mismatch loss, or return loss and this Java applet will not only convert among the values, but it will also present an animation of the incident, re
http://www.bessernet.com/Ereflecto/tutorialFrameset.htm
Replacement for the standard Windows calculator with many additional features.
http://www.rayslab.com/calculator/
http://www.opamplabs.com/cfl.htm
An RPN calculator applet and supporting Java library.
http://www.hpl.hp.com/personal/Hans_Boehm/crcalc/CRCalc.html
http://www.qsl.net/kd4sai/quad1.html
Want to know what resistor to use with some led? Take this calculator for a spin and see how it goes.
http://metku.net/index.html?sect=view&n=1&path=mods/ledcalc/index_eng
http://www.mogami.com/e/cad/coil-01.html
http://www.opamplabs.com/dbm-v-z.htm