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Old June 20th 07, 04:12 AM posted to rec.radio.amateur.antenna
Bryan Bryan is offline
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First recorded activity by RadioBanter: Jul 2006
Posts: 199
Default blocking radio waves

merlin-7 wrote:

Richard Clark wrote:
merlin-7" wrote:

Would simple aluminum foil work?


Hi Joe,

Sure, but bonding one sheet to the next overlapping one might "foil"
your goal. Few of us with dominant Y genes realize that aluminum foil
is wax (an insulator) coated on one side.


I understand it's typically a very thin plastic or paper, to which the
aluminum is laminated (http://en.wikipedia.org/wiki/Aluminium_foil).
Alternatively, aluminum window screen will work just as well, unless you're
working with frequencies approaching 19 GHz. This assumes screening of
1/16"x1/16" opening, and allowing for no more than 1/10 wavelength.

I understand this and was thinking about overlap and staples or possibley
tacks.


If (before you put the wall panels up) you attach a conductive strip of foil
or screen to the edges of the wall studs, you will have your overlap. If
you then use screws instead of nails, you can then (relatively) easily gain
access for future wiring changes.

I guess I also have the Y gene, the only reason I was thinking about foil
is that it is cheap and easy to work with. Wire screen would work also (I
think) but much simpler, glueing foil to plywood than screen.

If so what frequency range could I expect it to work in?


Most. Depends on the gaps. Staple it every inch, and it may work
from LF to VHF.

I know there is a term for a room like this but I can not rember

it..faraday
chamber?


Farady shield, room, chamber....

The shack will be 12 foot by 16 foot, right next to my 60' tower, with

HF
and 2m antennas on it. I have no idea how they will interact with such

a
building...


Are you doing the windows and doors too? Most doors have a gasket of
fringed fingers making contact with the conductive door.

No window, kinda bytes but needed.


Welded "chicken wire" with ¼x¼" openings over any windows will pass light
but will represent less than 1/10 wavelength up to 4725 MHz.


You did get me on the door, I didnt think of that one (DUH) I guess I

will
have to use a metal door or coat it with foil and strap it to the rest of
the foil.


Chomerics (http://www.chomerics.com/) and Tech Etch
(http://www.tech-etch.com/) -- among others -- produce compressible
shielding material that can be used to make a door RF-tight.

You need to choke EVERY wire penetrating the walls. Any exception and
your room will fill like an RF gong.

This is going to be a whole new problem.
With solar panel wire runs, coax runs for radio gear etc. I can deal with
that even if I have to disconnect everything when needed. I just need a RF
quiet room from time to time for searching for birdies and the like. I may
even section off a small area of the shack for that.( big enough for a
frequincy counter, a few other test instraments and the gear being tested.


In that case, think about using a suitably-sized cardboard box (coated with
conductive material). It has the potential of being folded up when not in
use!

Thanks
joe
KI4ILB

73's
Richard Clark, KB7QHC