Coil form made of high impact polystyrene 3.5″ diameter by 3″ long. Predrilled as supplied with Crystal Radio Kit 5 and Crystal Radio Kit 6. For AM radio, when used with the plastic variable capacitor dual section 266pf, use 40 turns of 22 AWG magnet wire approximately 40 feet. Includes a location to center tap ground for inductive coupling of longer antennas. You may want to experiment with how many turns on the small coil side work best. I typically use 5 to 10 turns. Other wire can be used with the coil form. The LC Inductance Calculator can be used to help determine the amount of wire and space required. On the large side of the coil there is approximately 1.25 inches and on the short side of the coil there is approximately 0.25 inches.
Click here for instructions for winding the coil.
1 – 3.5″ diameter x 3″ coil form (high impact polystyrene) predrilled
3 – 1/2″ #4 brass screws
9 – #4 brass nuts
6 – #4 brass washers