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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