2019-03-08 Winding a Ferrite Loopstick

also links to this in FB groups Building Transistor Radios and Ferrite Loopstick Exper.

I got some of these ferrite loopstick bars from Goldmine Electronics while the were on sale. They are the small kind that fit into pocket radios. Materials were the bar, a piece of paper for insulation, a roll of 32 AWG enameled copper wire, and heat from a soldering iron. See the attached photo.

I first cut a piece of paper to wrap around the bar and overlap a little. I used my soldering iron to melt some candle wax on the paper to hold it in place while I wound the wire. I used a short length of adhesive tape to hold the wire while I wrapped about ten turns. After that I melted some candle wax on the ten turns. I proceeded with the winding, periodically melting wax on the turns to hold them in place.

The finished coil measured a bit high so I removed turns to bring it to 680 microhenrys, which is what is used with the 140 pF ‘polyvaricon’ capacitors found in the cheap pocket radios.

I’m not sure if this FB group link works for everyone.

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