You can block electric fields and RF & microwaves with almost
any kind of sheet metal. It can have holes but not non-conductive seams.
If you can find really thick aluminum (I think 3/8" will do something, .5
inch
or more is ideal) you can block 60 Hz magnetic fields. Note if you are
close to the aluminum there could be strong field gradients near the
edges. If you put a piece close to the source the field should be canceled
somewhat
behind the sheet and also at
long distances. The field lines have to be perpendicular to the aluminum,
so you may need a directional meter or some knowledge that magnetic
fields wrap around wires etc.
You could also try the same trick with very thick copper cables (like what
the
power company uses; actual thickness needed depends on size of
the coil--I think about 3/4 inch will work for a 5 foot coil) arranged into
a Helmholtz coil. If the field you want
to cancel is uniform and the two coils are perpendicular to the field, you
get
a region of low field and low gradient between the coils. If you don't care
about
gradients you can do it with one coil, but theoretically the effects of
magnetic
fields usually come from gradients. Helmholtz described the ideal ratio of
coil separation, but I don't remember it.
Happy hunting,
Bill
On 10/12/07,
[hidden email] <
[hidden email]> wrote:
>
> Could I get mu-metal or similar from old dumped equipment if I were to
> go to
> my local waste tip ? any ideas if this stuff is in everyday equiment -
> probably not but worth asking, I know that its in recrding heads in very
> small
> amounts
>
> Paul UK
>
> [Non-text portions of this message have been removed]
>
>
>
[Non-text portions of this message have been removed]
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