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"Ferrite core" question.

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Electric Rain

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Hi, I want to build this circuit: http://home.maine.rr.com/randylinscott/feb98.htm and I'm having a problem with L1. It says,
"The inductor L1 is 3 turns of .5 mm wire on a 5 mm ferrite core." and I'm not sure what that means. "5 mm ferrite core" is somewhat broad, as there are many different types of ferrite cores, as I understand. ".5 mm wire"? Since when did they start measuring wire in mms? What happened to AWG? (Though, AWG stands for American Wire Gauge, and this isn't an American site... as I just now saw...) Is this supposed to be enamel wire? I'm confused... and I don't know where to find either of those things, the ferrite core or the wire. Can someone please help me here? Thank you.


P.S. I just looked up a chart, while typing this message, that tells you how many mms and inches AWGs size 50 to 10 are, and according to that, .5mm wire is about 24AWG, right?


Active Member
Amidon Associates makes and sells ( to anyone) ferrite and powedered iron cores of all shapes and sizes. I think I've seen what you need in their catalog - it's likely to be on-line or something you can order. My guess is that the "core" is more like a plastic form with a ferrite slug in it - though it could be something different. Dan's Small Parts, Jamece, Debco Electronics and Ocean State Electronics carry a lot of that stuff too.


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Wire, yes 0.5mm is about 24AWG.

As an alternative to using a ferrite core, you could use an aircored coil of about twice as many turns.
Just make a 6 turn coil on a 5mm former, and away you go!



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Don't build that FM stereo transmitter with its obsolete IC that has its RF frequency drifting all over the place. Its manufacturer has discontinued it and replaced it with a new IC with a quartz crystal and a phase-locked-loop for rock-solid RF frequency control and selection with dip-switches. All the new MP3 to car radio FM stereo transmitters use the new IC.

You can buy a kit (in Australia or New Zealand) with the new IC or get the project's plans on Google. Enter Stereo Micromitter in the search box and you will have a link to Silicon Chip magazine's entire project for free.

Hmmm, the kit is far away, expensive and it uses a tiny surface-mount IC. Last week I saw Maxell's finished product with the new IC, on sale for only $22.00CAN. I was tempted to buy it. :lol:
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