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Re: EMI Filter Freq



Original poster: "davep by way of Terry Fritz <twftesla-at-qwest-dot-net>" <davep-at-quik-dot-com>


> Original poster: "Jim Mora by way of Terry Fritz
><twftesla-at-qwest-dot-net>" <jmora-at-jetlink-dot-net>
 
> Hello All,

> I am about to first light my 8" coil. Assuming my toroid doesn't turn
> out to be too big, my Frs should be around 105 kHz.
 
>  I bought a couple of surplus TDK 20 amp filters (ZAC2220-11). Inet
> research reveals these drop 40dB in differential mode -at- 1.5 - 30 MHz, 
> 5 - 30 MHz, common mode.
 
> EMI question: will most of the noise the coil generates to the mains
> be close to the resonance Freq.

	A lot of it will

> (thus making these TDK's paper weights)

	They can't hurt.  Mostly.

> or am I likely to see much noise in shorter wavelengths in the form of
> harmonics?

	Yep.

	(The spec attenuation is IF USED PER THE TEST METHOD.  Usually,
	this means they must be mounted to an enclosure wall, with
	everything inside the enclosure.  If just inserted in the AC
	line, much of the noise will radiate around the filters.

	Use them, but if some escapes, that is the usual reason.)

	best
	dwp