Re: Need a custom Variable Inductor

Sep 17, 2003 4 Replies

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Tweetldee 22 years ago

That's a large inductance for OTS variable inductors. What range of inductance are you looking for?. J W Miller does custom jobs,

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-- Tweetldee Tweetldee at att dot net (Just subsitute the appropriate characters in the address)

Pardon if this is a bit off-topic, but you guys are as likely as anybody

have an answer for me. If I should ask somewhere else, please redirect me.
> :-)
>
> Does anybody know of a company that could build a ~100 mH variable choke,

moderately small quantities, say 900 per year. Or, does anybody know where

can buy an off-the-shelf part in these quantities?
>
> John O
>
>

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John O 22 years ago

Thanks for the lead, I'll check them out. We need about +/-5%.

These are used in classrooms, to teach students about phase shifts and tuned circuits. We could adapt to a range of values, considering our generator is limited to 20 kHz and lower.

-John O

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John Barnes 22 years ago

Can I suggest that you use a tapped inductor with a switch ?

L is proportional to the number of turns squared.

The inductance of an inductor of this type is dominated by the air gap. The magnetic properties of the air gap is constant and therefore repeatable.

I have seen ferrite pot cores with tuning slugs that were used before switched capacitor filters and dsps. I think that these are no longer available.

Regards,

John

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John O 22 years ago

Yep, that's what we're finding, too. I think we started using this kind of coil back when we put them in radio kits, which allowed us to do a bunch of RL & RLC tuned circuit experiments. Our search isn't going well, so it looks like the days of tuning resonant circuits under 20 KHz are over. :-)

John O

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CWatters 22 years ago

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