Re: Audio EMF coil?

From: John Woodgate (jmw_at_jmwa.demon.contraspam.yuk)
Date: 01/10/05 

Date: Mon, 10 Jan 2005 13:08:39 +0000

I read in sci.electronics.design that Tim Shoppa <shoppa@trailing-
edge.com> wrote (in <1105361603.082010.196320@c13g2000cwb.googlegroups.c
om>) about 'Audio EMF coil?', on Mon, 10 Jan 2005:
>> There is no practicable way of making a *uniform field*.
>
>The other extreme of terminology is "partial vacuum". There's no
>perfect vacuum, so of course all vacuums are partial vacuums...
>
>Interestingly, it is possible to do significantly better than the
>Helmholz coil for uniformity. See, for example,
>
>http://www.iop.org/EJ/abstract/0950-7671/43/7/311
>
>I think that actually winding the sperhical coils is left as an
>exercise for the reader!
>
First find you spherical room.

I have somewhere a paper about a circular room with a hollow pillar in
the middle which allowed a toroidal coil to be installed! But the very
uniform field is horizontal, of course, whereas hearing aid pick-up
coils are almost always vertical. 

-- 
Regards, John Woodgate, OOO - Own Opinions Only. 
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk