[RFI] RF tight rooms - somewhat OT

[Dale]

Roger,

A darned good chance that the room you were in was made by Lindgren RF Enclosures, and probably was one of their DEI rooms.  "DEI" = "Double Electrically Isolated", meaning that the inner and outer walls were separated from each other by wooden framing and the two sets of shields were joined at just one location: usually the panel where the power filters were located and a full length grounding stud shorted the shields together.  If not a Lindgren, the one of their competitors, but only Lindgren had the patents for the DEI concept.

73, Dale
WA9ENA 


-----Original Message-----
>From: "Roger (K8RI)" <k8ri at rogerhalstead.com>
>Sent: May 12, 2013 10:13 AM
>To: rfi at contesting.com
>Subject: Re: [RFI] RF tight rooms - somewhat OT
>
>On 5/11/2013 11:34 PM, n0tt1 at juno.com wrote:
>> Hi Gents,
>>
>> I know a crystal radio enthusiast in CA that lives near
>> a 50KW BCB radio station.  He's been having trouble
>> making Q-meter measurements on some of his hi-Q
>> coils using a HP Q-meter.  He's been making
>> experiments with various shielding methods
>> using an AM BCB portable radio as a detector.
>> He says that the best he's found so far is aluminum
>> foil, as long as the "seal" is tight.
>>
>> To make a room that is large enough for him and a bench
>> takes a LOT of foil.  The floor, ceiling, walls, floor and a
>> good seal on a screened door would be needed for a
>> really good RF room.  The power for the room would also
>> have to be filtered or he could use a computer's UPS.  The
>> shielding would be grounded, and the shielding, whether
>> it's say, chicken wire, AL screen, etc would have to be
>> bonded together at the corners.  Then the door would
>> have to be sealed as well (maybe metal weatherstripping
>> for that?).
>>
>> My question to the group is what, in your opinion, is the
>> best/cheapest RF-tight test room he could build for himself?
>> Has anyone on this list done that?
>
>
>Many years ago, in another life, (I spent 26 years working as an 
>Instrument tech, I did instrument calibration traceable to NBS.
>My work area and desk were inside a double wall screen room.  Thia was 
>about 20 X 10, or 12 feet,  The door was likewise double wall, with 
>what looked like large finger stock all the way around each layer. The 
>"fingers were about 3/4 or 1 inch wide and maybe 1.5 inches long.  The 
>door "cam locked" shit with about a 2' handle on the cam.  The room was 
>constructed out of panels that were ...Guessing...about 4' X 8" and 4" 
>thick. Frames were either brass or bronze as were all bolts were 1/2" "I 
>think".
>All electrical came in through a "filter panel" for lack of a better name.
>
>We could stand just feet apart with 10 watt HTs and still hear each 
>other with the door closed, but not camed shut.  As the handle was moved 
>you could watch the S-meters go down until no signal was left with the 
>cam fully closed
>
>This was a commercial system. Not exotic, but very effective for an example.
>
>73
>
>Roger (K8RI)
>>
>> 73,
>> Charlie, N0TT
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>
>
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