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Old 12-26-2009, 08:15 AM
JoeOh JoeOh is offline
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Default Is it possible to shield metal objects from MD's?

I don't have a MD yet to test this but I wonder if wrapping a few coins/rings/nails in a faraday cage will keep a MD from picking them up?

A faraday cage is a copper coil mesh that surrounds a box to keep radio signals from entering or leaving the "cage"

Any ideas?
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Old 12-26-2009, 08:29 AM
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I think the cage itself would be highly detectable.

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Old 12-26-2009, 09:01 AM
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Quote:
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I think the cage itself would be highly detectable.
I was thinking the same thing too but how the cage works is by absorbing the radio waves and translates them into heat because the cage is self-short circuiting when the radio waves induce a current in the wire mesh. It may not be a perfect shield, but if buried far enough it'll evade even the best MD.

i just wonder if someone had the forethought to maybe do this to better hide their stash.
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Old 12-26-2009, 09:07 AM
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It will not work. The MD will detect it if not out of range. RickO

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Old 12-26-2009, 09:43 AM
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Much like putting it in a lead safe... you cant tell what in it, but it will read the metal, if it hasnt been disc out. You trying to hide you cash in the back yard from your kids or Uncle SAM?

Dew

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Old 12-26-2009, 09:57 AM
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I know what a Faraday Cage is, I am a geek, LOL. But it won't work because it is used to contain not disperse like what you want it to do. It's design is for what's inside of the cage and not what's on the outside. Know what I mean.
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Old 12-26-2009, 10:55 AM
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Quote:
Originally Posted by JoeOh View Post
I was thinking the same thing too but how the cage works is by absorbing the radio waves and translates them into heat because the cage is self-short circuiting when the radio waves induce a current in the wire mesh. It may not be a perfect shield, but if buried far enough it'll evade even the best MD.

i just wonder if someone had the forethought to maybe do this to better hide their stash.
Well, that is not exactly how the Faraday cage works, but it's close enough.
The cage will protect its interior volume from an external, static --or slowly changing-- electrical field by setting up an equal but opposite electrical field on its surface. Thus whatever is inside, is protected from the external electrical influence. Note that the Faraday shield does not shield the insides from a dynamic or fast changing electrical field, or more importantly for our purposes, a slowly changing magnetic field (ie. a magnetic compass inside a Faraday cage will still point North), which is what the detector uses to induce an Eddy current on the target.

The Faraday cage, being built of highly conductive material will produce a very large Eddy current in response to the detector's transmit field and therefore generate a very large detectable signal, most likely overwhelming any possible signals produced by the targets inside the cage.

During a lightning storm, the inside of an an automobile is one of the safest place to be if you are outdoors, precisely because it is a Faraday cage of sorts. The electrical charge from a lightning hit is confined to the outside surface of the car thus protecting the passengers.

Check out this MIT physics video lecture on Faraday shielding.

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Old 12-26-2009, 11:37 AM
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Here's a human version of a faraday cage--these guys are working on a live 230,000 volt line, and need to block the large electrostatic field; they're wearing mesh metalic suits.

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