Use this calculator to find the inductances of the primary and secondary windings of a Mystery Crystal Set coil. Refer to the following diagram for the definition of the input variables.

In the diagram, primary turns are shown in blue. Secondary turns are shown in red.

For more information about the mystery coil please refer to the Mystery Crystal Radio page.

Conductor size is the size of the actual current carrying conductor, excluding insulation. For a close wound coil, set the pitch equal to the overall wire diameter including the insulation. For space wound coils, set the pitch to any larger value.

This calculator assumes that both primary and secondary conductors are the same size.

When calculating inductance, the variable pitch of the primary winding is taken into account.

To
calculate inter-winding capacitance, an estimate of the effective
dielectric constant **ε**_{R} is required. This
will be a combination of the dielectric constants of air, the wire
insulation and the coil form material. It's suggested that the
calculation be done with the minimum possible value of 1 (air
dielectric constant) and the maximum value (wire insulation, or coil
form material, whichever is greater). The two resulting capacitance
values will bracket the true value.

Back to:

Calculators

Radio Theory

Home

This page last updated: January 29, 2023

Copyright 2010, 2023 Robert Weaver