The Progressive Crystal Set

This set is called a "progressive" set since you start with the basic unit and can get progressively more sophisticated by adding a trap and antenna matching network.

The prototype version uses a homemade vernier made from a
CD and rubber grommet. The tapped trasformer will match many
different headset or speaker impedances.
of plexiglass and poly-coated wood.

The tuning knob shaft is in a panel mount piece made for a
1/4" shaft. The threaded part of a an old potentiometer could be used,
along with its 1/4 inch shaft.

Here is a rear view of the set. Notice the Bogen model T725 transformer.

Schematic of set.
Click for large view.