Coil

The coil and variable capacitor designs are a celebration of mathematical art and function. A sturdy 30-gauge magnetic wire is wrapped onto a 4" length 1.5" diameter clear plastic rod to effect 1000uH.

Snap balls to the two nib cells and a base panel.

Variable Capacitor

A middle triangle metal piece interweaves between two other pieces. A 0.25" diameter 0.25" length nib magnet "sandwiches" the two aluminum triangles from the attraction given by the far end steel triangle. Given the formula for capacitance = (permitivity constant of space) * (media dialectric constant) * Area / distance, the capacitance is maximized when the distance between the plates is minimized. Surprisingly, the best dialectric media turned out to be clear plastic tape used in everyday packaging. Swinging the triangle produces a variable capacitance from 29pf onto 311pf. It is capable of producing 367pf with the current triangular dimensions.

Snap the 1N34A detector diode, 0.33uf coupling capacitor, and diagonal 75K ohm rods with the extended nib magnet meeting the detector diode and .

Side panel mount

Snap the 7.5M ohm bias and 150K ohm resistors onto the 2N4401 transistor panel. Note the 0.33uf coupling capacitor feeds a signal to the transistor base.

Cube formation

In a break with tradition and to preserve a simplified cube design, the current sinks into the positive supply voltage.

Assemble the ear piece and 1uf series capacitor.

Coil mount

Mount the coil base (with coil atop) onto the cube. Assure all connections are secure and then connect the battery.

Final Assembly

Snap the antenna connector into the variable capacitor and detector diode node. The aligator clip can be fastened to a free-standing piece of metal such as a bookshelf rail.

At this point you are ready to listen to radio stations! Try different locations to get the best signal - outdoors gets the strongest signals. You may also touch the other end of the variable capacitor to effectivly make your body a "ground" and increase the signal strength.