[GreenKeys] What ever happened to "Pot Cores"?

[Jones, Douglas W]

I did an image search on pot cores and got piles of pictures of familiar looking cores -- think of a chunk of ferrite shaped like a pot with lump sticking up through the center, and a slot in the side where the pot handle would have been attached.  Wind a simple coil and sandwich it between two such pots and you have a ferrite core inductor.  You can get them with the two halves dead flat, designed to meet with no air gap.  A few have the central boss replaced by a third part, a ferrite cylinder that, if attached to a screw, can be screwed in and out to tune the pot.  Even the ones with no air gap and no movable center can be tuned a bit by rotating one half relative to the other half so the cut-outs in the side align more (higher inductance) or less.

Then I did an eBay search on "pot core" and got piles of them.  You can get piles and piles of new pots dirt cheap.  Kits with two pots and a plastic bobbin cost more, and pre-wound pot cores cost more.  There are new old-stock pot cores and brand new ones, fresh from some ferrite factory somewhere.

         Doug Jones
         jones at cs.uiowa.edu