Are MilliHenries obselete?

Toko makes them, they used to be available from Rapid Electronics but they don't seem to stock them any more. BEC still stocks them, though:

http://81.137.140.57/PG800/8fixed/p56.htm

Leon

Thanks

martin

Digikey (US): TK4411-ND, fixed 8.2mH US$3.75 TK3212-ND, tuneable 8.2mH US$4.74 M8255-ND, fixed shielded ferrite core 8.2mH US$2.95

Not all of these may be suitable for use in filters, especially audio range. I assume "20K-ish" refers to the cutoff frequency in Hz. Too bad--I know they used to handle a series of nice TDK coils that did work well at audio and weren't too pricy. Don't see them in the catalog now.

Cheers, Tom

I see 13 items total, *none* of them stocked items (not just out of stock at the moment).

Mouser has some different types. Fastron 07MFG-822J-50 and their house brand 43LH282, a couple thousand total currently in stock. They'll ship overseas fairly cheaply if you can't find them from a closer supplier.

Best regards, Spehro Pefhany

I suspect that these have become very 'low volume' items. A gyrator can be done with an op-amp, or one transistor, and in terms of production costs, is so much cheaper, and can actually often perform better, leading to the inductor, tending to die. I'd suspect it'd be easier to use the gyrator for this, than wait for the inductor...

Best Wishes

Or JW Miller 5800-822, Newark part number 28C9699:

Around a Dollar depending on quantities. IIRC Farnell in the UK works with them. Don't know about Espana though but it's all one Europe now I suppose.

Please enlighten me - what is it about a coil besides its inductance and maybe Q that might make one not suitable for audio range. Core properties? But what frequency it's at shouldn't affect the inductance - or do core losses just wreck the Q?

Thanks, Rich

The most important single detail that limits the frequency range of an inductor is its internal parallel capacitance that produces a self resonance at some frequency. You have to stay well below that frequency in order to have it look like a fixed value inductor.

The low frequency limit is the series resistance of the wire it is wound with. at some low frequency, it looks more like a resistor than an inductor.

So an inductor made with lots of turns of very fine wire has a lot of inter winding capacitance that limits the high end, and a lot of resistance that limits the low end.

On Thu, 15 Jun 2006 21:37:50 GMT, in sci.electronics.design Joerg wrote: snip

I spent ages going through the farnell site, their search engine isnt perfectt, its shut down at the moment......

But this job/idea is a "Joerg" type "2 weeks to LandFill" type specification and economy is essential, and hopefully it will annoy an awfull lot of people.

Anyway, back to LTspice

martin

Hello Martin,

Works fine from here (US). As I mentioned to John before this could simply be a DNS server that is down but that your ISP is using. Write down the direct IP addresses for sites you need a lot, then you can bypass that. For Farnell that would be:

http://194.152.77.229/

That looks like you'll have to scope out Asian source. That's where we sourced almost all our inductors. Sometimes a custom wound inductor from Taiwan cost less than a regular line item inductor of similar properties from a mainstream manufacturer.

I just wouldn't do that with electrolytics ;-)

Your RoHS stuff over there isn't exactly going to make this job any easier.

The parallel capacitance can be too high - if the self-resonant frequency of the coil is lower than the frequency you want to filter, the coil isn't much use. The tolerance on the inductance can also be a problem in some applications.

On Thu, 15 Jun 2006 18:01:51 -0400, John Popelish wrote: ...

Thanks! Rich

Thanks! Rich

...Yes!! You are to use 0.001 henry or 1,000 microhenry now.

;^)

Tim

I've just noticed that those 10RB Toko inductors I mentioned, that I use a lot, and are popular for a lot of amateur radio applications at AF, have a lower frequency limit of 10 kHz according to the BEC catalogue! It could be wrong, of course. I'll see if I can find a proper data sheet.

Leon