Featured Product Archive
The inventions and products featured on these pages were chosen either for their
uniqueness in the RF engineering realm, or are simply awesome (or ridiculous) enough
to warrant an appearance.
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There seems to be no such thing anymore as a simple formula for the physical
implementation of an electronic component. Back in the early days of electronics
discovery, frequencies were low and the precision needed for predicting the performance
of circuits was equally low. As techniques for component construction and circuit
analysis improved, more complete formulas were required to have theory match reality.
Simple equations like Wheeler's
 for a
single layer coil was good
enough. Now, the more complete Wheeler model of
 is often more useful (it is the one that produces
the result shown in the screen shot above). Be sure to conform to proper units.
Fortunately, some kind souls have seen to it that software is available free
of charge that removes the laborious task of typing long equations into a spreadsheet
or into a hand-held calculator. In this case, Coil64
(or the Coil32, 32-bit version) is available from Valery Kustarev. He provides calculations
for single layer coils with round or rectangular wire, multi-layer coils, multi-layer
coils with insulative material between the layers (like as found in transformers)
- all on round forms. It also covers rectangular forms. Coils on toroids, flat spirals,
and other types are included as well. Pretty nice for a free program! I have not
attempted to verify the accuracy of all the equations, so
caveat emptor.
The Coil32.net website also provides some theoretical
background on coils such as self-resonance, a handbook of common formulas, helical
resonators, and inductor color codes. A wire gauge table of dimensions, resistances,
diameters, etc., is handy when inputting parameters into the calculator.
Posted January 12, 2023
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