When I build my new shack, I was thinking about lining the inside of the
plywood with something, before it is installed, that would block outside
radio transmissions inside the shack.
Mostly in the 2 meter range and higher.

Would simple aluminum foil work?

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

If not any suggestions on material? The cheaper the better.

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



Thanks
Joe

On Tue, 19 Jun 2007 18:50:59 -0400, "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.

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.

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

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
On Tue, 19 Jun 2007 18:50:59 -0400, "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 this and was thinking about overlap and staples or possibley
tacks.

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.

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.

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.

Thanks
joe
KI4ILB

73's
Richard Clark, KB7QHC

On Tue, 19 Jun 2007 21:47:42 -0400, "merlin-7"
wrote:

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.

Hi Joe,

This is far easier to obtain through good grounding practices (as I've
discussed in the past hour in another thread).

73's
Richard Clark, KB7QHC

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

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

It is just plain aluminium, no wax, no paper, no plastic. Just think of the
results if you cooked something wrapped in a foil with a wax or plastic
coating!!! The matt finish on one side is just a result of the way that the
foil is rolled when being manufactured.

Jeff

Try "Bronze, or copper" screen- this is used in
"Radio Shops", to limit RF interference to services
being used, so as to test (proof of performance)
equipment , without causing interference to each
other !
A.K.A. "Faraday Shield" - Jim NN7K

merlin-7 wrote:
When I build my new shack, I was thinking about lining the inside of the
plywood with something, before it is installed, that would block outside
radio transmissions inside the shack.
Mostly in the 2 meter range and higher.

Would simple aluminum foil work?

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

If not any suggestions on material? The cheaper the better.

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



Thanks
Joe

"merlin-7" wrote in message
...
When I build my new shack, I was thinking about lining the inside of the
plywood with something, before it is installed, that would block outside
radio transmissions inside the shack.
Mostly in the 2 meter range and higher.

Would simple aluminum foil work?

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

If not any suggestions on material? The cheaper the better.

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



Thanks
Joe


Joe,

When working with a Faraday cage, remember that safety is of the utmost
importance. Any mains voltage electrical supply fed into the cage must come
in via an isolating transformer so that the mains voltages are floating.
This will reduce the risk of electric shock if a chassis becomes live with
respect to the earthed cage. It should not be possible to reach any
'ordinary' mains powered sockets, switches or devices outside the cage area
when you are within the cage. No external mains earth should be brought into
the cage area. The Faraday cage should be provided with its own completely
separate electrical earth. Mains sockets within the cage area should not
contain an earth connection.

British Standard 7671 contains some basic details but other equivalent
legislation applies in many countries.

It's not just about slapping up some tin foil around the walls, floors and
ceiling and then strapping it to the nearest convenient earth point. Your
safety and that of others who may enter the area are paramount.

Mike G0ULI

" When working with a Faraday cage, remember that safety is of the utmost
importance. Any mains voltage electrical supply fed into the cage must
come
in via an isolating transformer so that the mains voltages are floating.
This will reduce the risk of electric shock if a chassis becomes live with
respect to the earthed cage. It should not be possible to reach any
'ordinary' mains powered sockets, switches or devices outside the cage
area
when you are within the cage. No external mains earth should be brought
into
the cage area. The Faraday cage should be provided with its own completely
separate electrical earth. Mains sockets within the cage area should not
contain an earth connection.


That is certainly not the way any screened room I have worked is has been
wired, and sounds extremely dangerous. Not having the earths connected
inside the room is potentially lethal should a case go live.This is a
particular problem with a lot of test equipment where the input filtering
causes the case to float to 1/2 mains voltage without an earth. An RCD will
not protect you in this situation because of the isolating transformer.

Imaging the situation where you are conducting emc tests with the UUT on an
earthed copper sheet but all the test equipment is floating at 120V!!

It is also a common requirement to have test equipment outside the screened
room but connected to equipment inside, isolating transformers and the lack
of mains earth would complicate this set up immensely.

All the installations that I have seen have not used isolating transformers,
just filtering on the incoming mains with a mains earth connection.
Protection being provided by an RCD on the mains input.

Jeff

"Jeff" wrote in message
. com...

" When working with a Faraday cage, remember that safety is of the utmost
importance. Any mains voltage electrical supply fed into the cage must
come
in via an isolating transformer so that the mains voltages are floating.
This will reduce the risk of electric shock if a chassis becomes live
with
respect to the earthed cage. It should not be possible to reach any
'ordinary' mains powered sockets, switches or devices outside the cage
area
when you are within the cage. No external mains earth should be brought
into
the cage area. The Faraday cage should be provided with its own
completely
separate electrical earth. Mains sockets within the cage area should not
contain an earth connection.


That is certainly not the way any screened room I have worked is has been
wired, and sounds extremely dangerous. Not having the earths connected
inside the room is potentially lethal should a case go live.This is a
particular problem with a lot of test equipment where the input filtering
causes the case to float to 1/2 mains voltage without an earth. An RCD
will
not protect you in this situation because of the isolating transformer.

Imaging the situation where you are conducting emc tests with the UUT on
an
earthed copper sheet but all the test equipment is floating at 120V!!

It is also a common requirement to have test equipment outside the
screened
room but connected to equipment inside, isolating transformers and the
lack
of mains earth would complicate this set up immensely.

All the installations that I have seen have not used isolating
transformers,
just filtering on the incoming mains with a mains earth connection.
Protection being provided by an RCD on the mains input.

Jeff



Jeff

If you are working surrounded on all sides by earth potential and you touch
a mains live wire, then the current has a path through you to earth. In
theory, only the phase (or live) wire represents a serious hazard but in the
event of a chassis going live, this could be fatal.

By having mains voltages floating, earthing either side of the isolated
mains accidently to earth should not result in a lethal shock as the
potential on the touched wire only will move down to earth. An RCD is not
needed because although one side of the mains has become earthed through
you, there should be no return path unless you are touching the other mains
wire somehow, in which case you would get a shock whether you were in
contact with earth or not!

110v Isolating transformers with their central point earthed are used on all
building sites in the UK to limit shock voltages to 55v AC. In this case the
transformer is earthed because it is impossible to work away from other
natural earth points, girders, trusses, rods, etc. To a large extent this
also prevents the risk of inappropriate equipment designed only for domestic
purposes being used on site.

For a Faraday cage installation, the mains supply should be completely
isolated and floating using a double insulated approved transformer, no
autotransformers.

I previously worked in a test environment where isolating transformers and a
rubber mat were regarded as adequate protection against shock. Times change.
A proper Faraday cage setup does represent quite a complex environment to
design, is potentially (sorry) very dangererous to work in and so it is
worth looking at the official documents available for their recommendations.
In the UK at least, the standards are recommendations rather than statutory
requirements although you will have a tough time in court if someone is
injured or killed as a result of non-compliance.

Before attempting to set up this sort of testing room, consider carefully
what your requirements are, the safety implications and design accordingly.
Sticking a load of earthed foil and mesh around the inside of a shed is only
the start.

Better safe than crispy fried critter.

Mike G0ULI