where can I get 50-300 uH adjustable coils?
I'm trying to build my friend a Theremin for Christmas (obviously wont be finished by then), and I can't seem to find a few parts for it.
Its a design that comes from Popular Electronics November 1967 Issue (http://bit.ly/gNaQVH). It calls for 50-300 uH adjustable coils and I can't find 'em anywhere.
I have found adjustable coils/variable inductors but I haven't been able to find any with this inductance rating.
Aside from building my own, I'm at a loss here.
That's microHenries, correct?
Here's a link to my variable-inductor wah project. The inductor I used was from a reclaimed Wurlizer organ, with a range between 550-70 uH.
Others researching replicating this have found that Morelock's Organ Parts sells NOS inductors, including this one for about $5. It's very close to your needs. Morelock's may even have one that's spot-on. I don't have the link, but they have a website.
Incidentally, the inductor uses two coils either in series or parallel to multiply the mutual inductance (google "vario-coupler"), so it's possible (?) that one coil alone might be close to 300-50uH...
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One more comment: 550 to 70mH is so close your speced part, it's likely that a small adjustment of the associated capacitance (as it's used in an LC tank) would more than compensate.
In fact, with caps being 20% tolerance, it's probably adequate, as-is.
Would be better to find them cheaper than $5, but that's VERY cheap for a variable inductor in the micro range...
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I forgot, there's an image of the inductor on my Orangeboard:
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Wow! Nice. That's back when Pop. Elec. was a great magazine.
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I'd look in your area for an electronics surplus store. they're online as well...
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I'd build my own, but I like inductors. I'd use an RM or P series system from Ferroxcube to do it.
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