Test Coil For Experimenting With Crystal Sets.
Today I wanted to experiment a little with antenna matching for one of my crystal sets. I had the capacitor but no suitable coil for testing my bright idea. This is how this little project got going.
My test coil is wound on a 3 inch mailing tube which I painted with black lacquer a while ago. There are 75 turns of around 22 gauge wire on this coil The wire was surplus so I am not sure of the gauge. Anyway the coil is tapped every ten turns except for the winding on the end, which is 5 turns. Having a winding tapped at half the number of turns of my other taps allows me to have nearly double the inductance values for this coil.
I wound the coil without regard to the specific inductance values. What ever I ended up with was fine with me. After winding the coil I took a scrap piece of Garolite® and drilled 11 holes. Two for mounting the terminal block to the coil and 9 for the windings. I staggered the winding screws to allow for a little extra room.
Now I have a little coil I can use to play around with a couple of circuits. Below are the inductance values I ended up with. Use what you have laying around and how you feel to make your own test coil.
Good luck ~ Dave, N2DS
Terminals Inductance 1 - 2 5 µH 2 - 3 19 µH 1 - 3 35 µH 2 - 4 55 µH 1 - 4 80 µH 2 - 5 106 µH 1 - 5 133 µH 2 - 6 164 µH 1 - 6 164 µH 2 - 7 194 µH 2 - 7 227 µH 2 - 8 259 µH 1 - 8 295 µH 2 - 9 360 µH 1 - 9 396 µH