Faraday Cage

>From: David Trimmell <dwt-at-efn-dot-org>

>I am needing to build a Faraday cage to hopefully reduce the 
>interference my coil causes with my telephone and the AM radio reception 
>around my house.  No neighbor complaints, but just encase the FCC is 
>listening.  My question is: how fine of a wire mesh would you need to 
>block the RF from a coil running from 200 to 350 kHz?  And the 
>associated "noise"?
	OK.  I have worked at pro level here on this in the past.  For the
	fundamental 'any' practical mesh size is ok.  Rule of thumb for
	'FCC Emissions' is 'single longest dimension' no langer than 1/10th
	of a wavelength.  A wavelength at 200KHz is what, 1.5 KM?

	So any metal screening, chicken wire, etc should do.  (The 'threat
	level' from a tesla coils is higher, but the mesh size is WAY UNDER
	so the attenuation is ok.)

	BUT.  The 'single longest dimension' is important.  Say there is a
	door, screen covered, 6 ft by 3 ft.  closed it STILL 'looks' like
	a 6ft opening, the single LONGEST dimention governs, so open or closed
	its a 6 ft hole.  Unless...  The edges are bonded, finger stock, or
	something like that, to 'rub' when closed.  (It may be that the
	attenuation of a 6ft opening would be enough, but i amused to higher
	freqs in FCC work, and have seen 'ungasketed' doors fail.)

	ALL wires in and out must be filtered, with filters 'bonded' to the
	cage wall.  No Exceptions.  (OK OK.  Fiber otic penetrations are
	ok....8)>>)  If there is already a filter on the line side of the
	PSU it becomes somewhat irrelavant, since the noise 'radiates around'
	it, and rides happily out on the power supply lines.