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@rogerhalstead.com>
>Sent: May 12, 2013 10:13 AM
>To: rfi@contesting.com
>Subject: Re: [RFI] RF tight rooms - somewhat OT
>
>On 5/11/2013 11:34 PM, n0tt1@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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