I finally ordered a bunch of parts to start playing with a simple crystal radio. The main two I needed were some germanium diodes and high impedance earphones. I figured I could wind the coil and build a variable capacitor (though I ordered a small inductor kit and also some 365pF variable caps).
The germanium diodes came in but the earphones did not, and I would like to play with this over Thankgiving with my daughter. So I am thinking to use some earphones I have around here. I think they are 32Ω, but they might only be 16Ω. So I want to make a transformer to scale the impedance. Ideally, if I use a turns ratio of 10:1 that would get me either 3200Ω or 1600Ω, either of which is probably enough. Not looking for performance, here, just that it work.
I have some enameled magnet wire - a few different sizes in the 28 AWG range - to work with. My question is, how do I determine how many turns to use -- or at least a minimum number of turns that is likely to work. Also, can I use an air core form, such as an empty toilet paper roll? Would a smaller diameter, such as a soda straw, work better? Would it work better if it were wound on an iron (or steel) rod. I have some large nails (3/8" diameter) I could use.
I'll be experimenting a lot, but I'm looking for some thoughts to guide my starting point. Thanks!
The germanium diodes came in but the earphones did not, and I would like to play with this over Thankgiving with my daughter. So I am thinking to use some earphones I have around here. I think they are 32Ω, but they might only be 16Ω. So I want to make a transformer to scale the impedance. Ideally, if I use a turns ratio of 10:1 that would get me either 3200Ω or 1600Ω, either of which is probably enough. Not looking for performance, here, just that it work.
I have some enameled magnet wire - a few different sizes in the 28 AWG range - to work with. My question is, how do I determine how many turns to use -- or at least a minimum number of turns that is likely to work. Also, can I use an air core form, such as an empty toilet paper roll? Would a smaller diameter, such as a soda straw, work better? Would it work better if it were wound on an iron (or steel) rod. I have some large nails (3/8" diameter) I could use.
I'll be experimenting a lot, but I'm looking for some thoughts to guide my starting point. Thanks!