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Test Coil For Experimenting With Crystal Sets.

Test coil

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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

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