Originally posted by Turion
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I remember some old C-band satellite receivers from the 70's/80's/early 90's that had a medium grey casting that was partitioned into internal compartments and they had circuit boards mounted inside the partitions with an aluminum top cover that was attached with screws into the casting. The assembly then was fitted into a metal and plastic cabinet to make it look better and hold the user controls and meters. At first glance one might think the casting was aluminum but the unit was relatively heavy for its size. I'm thinking that casting might have been permalloy to shield the internal microwave signals from each other and any external EM fields. That's how it was used in aviation magnetic compasses.
Since permalloy is mostly nickel and iron I think the coating might be zinc to prevent corrosion. If you scratch the casting it should be bright silver underneath the coating and it would be highly magnetic if it is permalloy or not magnetic at all if aluminum.
I'm thinking I might be able to cut a 6" X 1 3/4" piece out of one of those to make an armature but haven't found one yet.
Or if anyone remembers a make and model of such a C-band receiver that might help me narrow down the search. I opened up a DirecTV receiver a few years old and they no longer use the casting for shielding in the modern units.
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