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Re: MIT study on aluminum foil hats

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On 11/16/2015 1:43 PM, jimp@specsol.spam.sux.com wrote:
> benj <none@gmail.com> wrote:
>> On 11/16/2015 11:12 AM, gilber34 wrote:
>>> On 11/15/2015 8:33 PM, jimp@specsol.spam.sux.com wrote:

>>>>> skin effect is only one part of the problem, re-radiation from the other
>>>>> side is another, a reason most shield rooms have two screens attached at
>>>>> a single point between them. and also lack of sufficient attenuation in
>>>>> material.  Gov switched from copper to galvanized steel sheet for many
>>>>> of their SCIFs, much cheaper, + better attenuation.  Need to knock it
>>>>> down by 90 to 150 Db

>>>> Re-radiation from the other side of a closed, solid conductor is
>>>> impossible
>>>> for practical sheet metal of any kind.
>>>
>>>
>>> True, if the solid conductor is thicker than skin depth, and has some
>>> Iron content to attenuate down to 1KHz.   But the seams, doors can be a
>>> challange, etc.

>>> It is a matter of how much attenuation you want, 20 Db or 150 Db
>>> more material, more layers, more attenuation. (easier as you go up in
>>> frequency)
>>>
>>> Try cutting off a DC magnetic field from a PMT tube

>> Simple. Just need lower resistance.
>
> Mu metal.
>
> Been there, done that for a chamber that had to exclude RF as well
> as magnetic fields.
>
>

Been there, done that too, built a small chamber worked well down to 
about 1 MHz, got a measured 149 Db isolation at 400-500 Mhz, .

and the PMT was a hemispherical 8 inch looking up, had lots of room used 
galvenized sheet metal box, and mu metal wire in a grid across the top. 
the mu metal sheet foil very pricy. slight loss if field tilts beam 
path, can turn tube 90 degrees, for less effect too.

anyhow the OP was about MIT and their Al Foil Deflecter Beniees
apperently the Chinese have patented it this year.

see this site for the latest;
http://zapatopi.net/afdb/

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MIT study on aluminum foil hats Sam Wormley <swormley1@gmail.com> - 2015-11-15 14:59 -0600
  Re: MIT study on aluminum foil hats jimp@specsol.spam.sux.com - 2015-11-15 21:05 +0000
    Re: MIT study on aluminum foil hats "Ross A. Finlayson" <ross.finlayson@gmail.com> - 2015-11-15 13:24 -0800
      Re: MIT study on aluminum foil hats "Ross A. Finlayson" <ross.finlayson@gmail.com> - 2015-11-15 13:26 -0800
      Re: MIT study on aluminum foil hats jimp@specsol.spam.sux.com - 2015-11-15 21:58 +0000
  Re: MIT study on aluminum foil hats Fabian Russell <root@localhost.localdomain> - 2015-11-15 21:37 +0000
    Re: MIT study on aluminum foil hats jimp@specsol.spam.sux.com - 2015-11-15 22:04 +0000
      Re: MIT study on aluminum foil hats Fabian Russell <root@localhost.localdomain> - 2015-11-15 23:00 +0000
        Re: MIT study on aluminum foil hats jimp@specsol.spam.sux.com - 2015-11-15 23:05 +0000
  Re: MIT study on aluminum foil hats gilber34 <fafa@invalid.com> - 2015-11-15 16:06 -0600
    Re: MIT study on aluminum foil hats jimp@specsol.spam.sux.com - 2015-11-15 22:57 +0000
      Re: MIT study on aluminum foil hats gilber34 <fafa@invalid.com> - 2015-11-15 19:51 -0600
        Re: MIT study on aluminum foil hats jimp@specsol.spam.sux.com - 2015-11-16 02:33 +0000
          Re: MIT study on aluminum foil hats gilber34 <fafa@invalid.com> - 2015-11-16 10:12 -0600
            Re: MIT study on aluminum foil hats "nuny@bid.nes" <Alien8752@gmail.com> - 2015-11-16 09:28 -0800
            Re: MIT study on aluminum foil hats benj <none@gmail.com> - 2015-11-16 12:52 -0500
              Re: MIT study on aluminum foil hats jimp@specsol.spam.sux.com - 2015-11-16 19:43 +0000
                Re: MIT study on aluminum foil hats benj <none@gmail.com> - 2015-11-16 21:55 -0500
                Re: MIT study on aluminum foil hats gilber34 <fafa@invalid.com> - 2015-11-16 23:04 -0600
            Re: MIT study on aluminum foil hats jimp@specsol.spam.sux.com - 2015-11-16 19:39 +0000
  Re: MIT study on aluminum foil hats HVAC <mr.hvac@gmail.com> - 2015-11-16 03:24 -0800
    Re: MIT study on aluminum foil hats HVAC <mr.hvac@gmail.com> - 2015-11-16 03:26 -0800
      Re: MIT study on aluminum foil hats benj <none@gmail.com> - 2015-11-16 12:42 -0500
    Re: MIT study on aluminum foil hats benj <none@gmail.com> - 2015-11-16 12:40 -0500

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