Crystal Radio Project - Taps

[lynnewillis1]

I am trying to help my 8th grader with the crystal radio project that he got directions for off of Science Buddies. We are having trouble "tapping" the wire - he is clipping/cutting the wire when he tries to clip the insulation off of it. Can you give us some pointers on the best way to do this? Do we need a special tool? We would greatly appreciate any help you can offer.

[rmarz]

I looked at the Science Buddies project for this experiment (https://www.sciencebuddies.org/mentorin ... p014.shtml) and it appears that the loop brought out for the tap probably wouldn't need to be a continuous wire. If you brought out enough wire for a 1/2" loop, the wire could be cut, the insulation stripped from each end, and the stripped ends twisted together. I never built this particular radio, but in my youth built literally dozens of similar crystal sets. Many used the old galena crystal with a 'cat's whisker' contact. Germanium diodes like the 1N34 simplify the task.

Rick Marz

[deleted-71588]

What kind of insulation is on the wire you are using? What kind of tool are you attempting to strip it with?

Stripping PVC insulated wire with a pocket kife is a skill that isn't too hard to master with a bit of practice on some scrap wire. Hold the knife body in the palm of the hand with the fingers with the blade at a small acute angle (about 20 degrees for this guage) to the wire with the thumb on opposite side of the wire pressing the wire against the blade. With practice, you should be able to slice off the insulation down to the wire without nicking it. Once you have an opening showing bare wire, you can bend the wire and insulation in opposite directions and cut the insulation away from the wire on both ends of the opening.

If it is a soft PVC insulation, you could melt it with a soldering iron. If it has a teflon or nylon outer layer of insulation, it will be hard to work with for this project.

Enamel insulated wire is best stripped by scraping, pulling or dragging the knife edge at a small acute angle and you have to do this several times rotating the wire so that it goes against places where the lacquer enamel is still adhering.