Make a Crystal Radio Coil Form

This Instructable will help you to make a strong and firm tube on which to wind a wire coil.

Crystal radios, or “foxhole” radios are still fun, a hundred years after boys and girls began making them in the early years of radio. While many things will serve as the coil form needed, it seems that nearly everyone has access to the old standby, toilet paper tubes. However, a single one is rather weak and collapsable. Here’s a way to make a good coil form with almost no expense.

Start by gathering the tools and materials.

2-3 toilet paper tubes

A scissor

White glue

A pencil or pen

A couple of disposable plastic shopping bags

First, using the scissors cut 1-2 of the tubes in a straight line, from end to end, keeping one of the tubes whole and uncut.

Insert one of the sliced tubes into the whole tube, and mark the “overlap” with the pen.

Remove and cut the inside tube from end to end, probably about a 1/4 inch slice. This will allow the inside to tube to fit with no overlap. Smear glue on the whole outside of this one and slide it in, pressing to make contact with the outside tube.

Repeat with the third tube, cutting a bit more off along the overlapping edge. Glue it in the same way and stuff a disposable plastic shopping bag inside to help press the whole assembly together as the glue dries.

When the glue is dry, adjust any overhangs with the scissors and proceed with the radio of your dreams.