This page lets you do calculations for single layer air cored
coils using the solenoid formula:

L (microH) = (r^{2}n)^{2}) /
(9r + 10 l)

Here r and l are the coil radius and length
in inches and n is the number of turns. Note that
strictly r is not the inside radius of the coil, i.e. that
of the former, but is measured to the centre line of the winding.

You must specify the diameter of the coil, and
its length. You may then either specify the number of turns
and calulate the resulting inductance (`Model'), or specify the
required inductance and calculate the number of turns (`Design').

Design Mode

In this mode the number of turns required
for a given inductance is calculated and a wire gauge recommended,
provided this is less than 40swg. If the length you request
would require a smaller gauge than this, then you will get a warning message.

Notice that this program does not at present allow
you to design a close wound coil directly, although the actual length
of winding using the suggested wire gauge is calculated.

Because winding fractional turns is a bit tricky, Design mode will
round to the nearest whole turn in the results box, although
the fractional number of turns is reported in the large box.

Modelling Mode

This will calculate the exact inductance of a coil with given
former diameter, length, number of turns and, optionally, wire
gauge.

If you click `Model' after `Design' you can
calculate the actual inductance with a whole number of turns and
allowing for the wire diameter.