need variable inductor

[John M]

I'm working on a metal detector project and have run into a problem. It's all built except one part - a variable inductor (Miller #6196A), .054 millihenry to .5 millihenry powdered iron core. That's all I know about it.

I need two, or I need to know what kind of core form and how many windings are needed to make an equivalent part. Or if there is an equivalent available somewhere. I have searched the internet thoroughly with no luck.

I'm a beginner at building electronic projects, so I don't really understand the inductance formulas I've found. Any help would be greatly appreciated. Thanks!

The project is from this website - http://www.geocities.com/Paris/Musee/3308/About/md_plans_ocr.pdf

 

[Agent 009]

I bought once a variable inductor though i didn't figure out how it worked, cause it was all bundled in a tiny case... I know this isn't much of use, but at least, put in mind that u can find variable inductors :lol: !

 

[Nigel Goodwin]

They are quite simple (and common), they have a metallic core which screws in and out - either iron dust (ferrite) or brass. Iron dust increases inductance, brass decreases it.

 

[Agent 009]

yeah, i've seen one of those, but i thought there's another type...