Hello -

I'm writng some software to run on a PocketPC with a built-in GPRS phone,
and I need to test the software when the GPRS signal is weak, intermittent
or non-existent. The cheapest way to do this seems to be to build a Faraday
cage with adjustable leakiness. It needs to have some holes in it so that I
can see the screen and tap it with a stylus. Unfortunately I'm working at a
location that has excellent GPRS coverage.

I've already confirmed that a metal tin that previously contained Marks and
Spencers chocolate biscuits is 100% effective, but I can't see through it or
operate the PocketPC. I've also tried making a cage out of a single sheet of
galvanized chicken wire with 12mm square holes, held together with plastic
cable ties, with overlapped joints. This only caused a small amount of
attenuation, the PocketPC hardly noticed. I'm guessing that it failed
because the diagonals of the holes are larger than 10% of the wavelength
that GPRS uses (1800MHz ?) or because the plastic cable ties don't provide
good conductivity at the joints.

Before I go out and buy some expensive perforated copper sheet, can anyone
offer advice on improvements?

Thanks

Before I go out and buy some expensive perforated copper sheet, can anyone
offer advice on improvements?

Thanks

Have you tried covering the open side of the tin with two layers of
chicken mesh slightly offset.

Dave

"Dave Stanton" wrote in message
news

Before I go out and buy some expensive perforated copper sheet, can
anyone
offer advice on improvements?

Thanks

Have you tried covering the open side of the tin with two layers of
chicken mesh slightly offset.

Dave

Thanks for the reply. I did briefly try that, but it wasn't very successful.
I think part of the problem is that the biscuit tin appears to have a layer
of laquer on it, and the chicken wire has a slightly oxidized Zinc coating,
so it may be difficult to get a good electrical connection between the two,
which I understand is important. I think I will try this again.

Dave Stanton wrote:
Before I go out and buy some expensive perforated copper sheet, can anyone
offer advice on improvements?

Thanks

Have you tried covering the open side of the tin with two layers of
chicken mesh slightly offset.

Dave
would it help if you laid on your back and looking up at the P/PC
covered it with tin so you can still operate it inside the tin?

Simon wrote:

I'm writng some software to run on a PocketPC with a built-in GPRS phone,
and I need to test the software when the GPRS signal is weak, intermittent
or non-existent. The cheapest way to do this seems to be to build a Faraday
cage with adjustable leakiness. It needs to have some holes in it so that I
can see the screen and tap it with a stylus. Unfortunately I'm working at a
location that has excellent GPRS coverage.

I've already confirmed that a metal tin that previously contained Marks and
Spencers chocolate biscuits is 100% effective, but I can't see through it or
operate the PocketPC. I've also tried making a cage out of a single sheet of
galvanized chicken wire with 12mm square holes, held together with plastic
cable ties, with overlapped joints. This only caused a small amount of
attenuation, the PocketPC hardly noticed. I'm guessing that it failed
because the diagonals of the holes are larger than 10% of the wavelength
that GPRS uses (1800MHz ?) or because the plastic cable ties don't provide
good conductivity at the joints.

Before I go out and buy some expensive perforated copper sheet, can anyone
offer advice on improvements?

Some fine wire mesh, such as:
http://rswww.com/cgi-bin/bv/initSession.jsp?goto=/rswww/subRangeAction.do&catoid=-1600768109&store=uk


--
Grunff

On Wed, 5 Apr 2006 18:52:22 +0100, Simon wrote:

can anyone offer advice on improvements?

How about some 6mm weldmesh?

Used for bird feeders, get it from the garden centre. If not, I'm sure
I've got an offcut - how big are we talking?

--
Nigel M

In uk.d-i-y Simon wrote:
Hello -

I'm writng some software to run on a PocketPC with a built-in GPRS phone,
and I need to test the software when the GPRS signal is weak, intermittent
or non-existent. The cheapest way to do this seems to be to build a Faraday
cage with adjustable leakiness. It needs to have some holes in it so that I
can see the screen and tap it with a stylus. Unfortunately I'm working at a
location that has excellent GPRS coverage.

Simply purchase a new large fridge, and open the door a crack.

"Simon" wrote in message
...
Hello -

I'm writng some software to run on a PocketPC with a built-in GPRS phone,
and I need to test the software when the GPRS signal is weak, intermittent
or non-existent. The cheapest way to do this seems to be to build a
Faraday
cage with adjustable leakiness. It needs to have some holes in it so that
I
can see the screen and tap it with a stylus. Unfortunately I'm working at
a
location that has excellent GPRS coverage.

I've already confirmed that a metal tin that previously contained Marks
and
Spencers chocolate biscuits is 100% effective, but I can't see through it
or
operate the PocketPC. I've also tried making a cage out of a single sheet
of
galvanized chicken wire with 12mm square holes, held together with plastic
cable ties, with overlapped joints. This only caused a small amount of
attenuation, the PocketPC hardly noticed. I'm guessing that it failed
because the diagonals of the holes are larger than 10% of the wavelength
that GPRS uses (1800MHz ?) or because the plastic cable ties don't provide
good conductivity at the joints.

Before I go out and buy some expensive perforated copper sheet, can anyone
offer advice on improvements?

As a general rule of thumb, grid spacing should be less than (or equal to)
1/10 the wavelength of the highest frequency you are interested in blocking.

Marcus

Have you tried covering the open side of the tin with two layers of
chicken mesh slightly offset.

Dave

Thanks for the reply. I did briefly try that, but it wasn't very successful.
I think part of the problem is that the biscuit tin appears to have a layer
of laquer on it, and the chicken wire has a slightly oxidized Zinc coating,
so it may be difficult to get a good electrical connection between the two,
which I understand is important. I think I will try this again.

What you need to do is use plenty of nuts and bolts with large washers to
hold the mesh in place and yes, scrape the laquer off. Blimey this is
taking me back a few years to Amateur Radio days.
RF will leak around holes so good firm electrical contact is essential.

Dave

"Simon" wrote in message
...
Hello -

I'm writng some software to run on a PocketPC with a built-in GPRS phone,
and I need to test the software when the GPRS signal is weak, intermittent
or non-existent. The cheapest way to do this seems to be to build a
Faraday
cage with adjustable leakiness. It needs to have some holes in it so that
I
can see the screen and tap it with a stylus. Unfortunately I'm working at
a
location that has excellent GPRS coverage.

I've already confirmed that a metal tin that previously contained Marks
and
Spencers chocolate biscuits is 100% effective, but I can't see through it
or
operate the PocketPC. I've also tried making a cage out of a single sheet
of
galvanized chicken wire with 12mm square holes, held together with plastic
cable ties, with overlapped joints. This only caused a small amount of
attenuation, the PocketPC hardly noticed. I'm guessing that it failed
because the diagonals of the holes are larger than 10% of the wavelength
that GPRS uses (1800MHz ?) or because the plastic cable ties don't provide
good conductivity at the joints.

Before I go out and buy some expensive perforated copper sheet, can anyone
offer advice on improvements?

Thanks


========================
Have you considered using a box made from the reinforcing mesh used with car
body filler? It's very easily shaped and reaily available.

Cic.

Or find a friend with a steel Narrowboat or just take the whole lot to
Braunston, Northamptonshire. The signal is next to nothing by the canal
there.
Brian

"Simon" wrote in message
...
Hello -

I'm writng some software to run on a PocketPC with a built-in GPRS phone,
and I need to test the software when the GPRS signal is weak, intermittent
or non-existent. The cheapest way to do this seems to be to build a
Faraday
cage with adjustable leakiness. It needs to have some holes in it so that
I
can see the screen and tap it with a stylus. Unfortunately I'm working at
a
location that has excellent GPRS coverage.

I've already confirmed that a metal tin that previously contained Marks
and
Spencers chocolate biscuits is 100% effective, but I can't see through it
or
operate the PocketPC. I've also tried making a cage out of a single sheet
of
galvanized chicken wire with 12mm square holes, held together with plastic
cable ties, with overlapped joints. This only caused a small amount of
attenuation, the PocketPC hardly noticed. I'm guessing that it failed
because the diagonals of the holes are larger than 10% of the wavelength
that GPRS uses (1800MHz ?) or because the plastic cable ties don't provide
good conductivity at the joints.

Before I go out and buy some expensive perforated copper sheet, can anyone
offer advice on improvements?

How about putting it in a microwave oven (with the microwave off,
obviously!)

You could control it with PocketVNC with a cable connected to it if you need
to operate it with the door closed.
You could just open the door a bit the get the required signal strength.

Sparks...

In article , Simon
writes
Hello -

I'm writng some software to run on a PocketPC with a built-in GPRS phone,
and I need to test the software when the GPRS signal is weak, intermittent
or non-existent. The cheapest way to do this seems to be to build a Faraday
cage with adjustable leakiness. It needs to have some holes in it so that I
can see the screen and tap it with a stylus. Unfortunately I'm working at a
location that has excellent GPRS coverage.

I've already confirmed that a metal tin that previously contained Marks and
Spencers chocolate biscuits is 100% effective, but I can't see through it or
operate the PocketPC. I've also tried making a cage out of a single sheet of
galvanized chicken wire with 12mm square holes, held together with plastic
cable ties, with overlapped joints. This only caused a small amount of
attenuation, the PocketPC hardly noticed. I'm guessing that it failed
because the diagonals of the holes are larger than 10% of the wavelength
that GPRS uses (1800MHz ?) or because the plastic cable ties don't provide
good conductivity at the joints.

Before I go out and buy some expensive perforated copper sheet, can anyone
offer advice on improvements?

Thanks



You'll need quite a fine mesh to do that!. And no gaps either. Solder
all of them and operate the keys with non conductive rods of a very
small diameter.

Try the lower sub basement floors of a car park or concrete building.

Or failing that take the whole shooting match out into Norfolk where
you'll fine a lack of GSM GPRS UMTS and much else!....
--
Tony Sayer

The message
from "Simon" contains these words:

Before I go out and buy some expensive perforated copper sheet, can anyone
offer advice on improvements?

Door from an old microwave should make a nice seethrough radio-opaque
wossname.

--
Skipweasel
Pay no attention to that man behind the curtain.

In an earlier contribution to this discussion,
Simon wrote:

Hello -

I'm writng some software to run on a PocketPC with a built-in GPRS
phone, and I need to test the software when the GPRS signal is weak,
intermittent or non-existent. The cheapest way to do this seems to be
to build a Faraday cage with adjustable leakiness. It needs to have
some holes in it so that I can see the screen and tap it with a
stylus. Unfortunately I'm working at a location that has excellent
GPRS coverage.

I've already confirmed that a metal tin that previously contained
Marks and Spencers chocolate biscuits is 100% effective, but I can't
see through it or operate the PocketPC. I've also tried making a cage
out of a single sheet of galvanized chicken wire with 12mm square
holes, held together with plastic cable ties, with overlapped joints.
This only caused a small amount of attenuation, the PocketPC hardly
noticed. I'm guessing that it failed because the diagonals of the
holes are larger than 10% of the wavelength that GPRS uses (1800MHz
?) or because the plastic cable ties don't provide good conductivity
at the joints.

Before I go out and buy some expensive perforated copper sheet, can
anyone offer advice on improvements?

Thanks

I've got an excellent Faraday Cage. It's better known as a caravan!
--
Cheers,
Roger
______
Please reply to newsgroup.
Reply address IS valid, but not regularly monitored.

"Simon" wrote in message
...
Hello -



Before I go out and buy some expensive perforated copper sheet, can anyone
offer advice on improvements?

Try a old biscuit tin (a metal one)- you may find just putting the top in
with a "crack" open is enough.

--
73
Brian
www.g8osn.org.uk

Guy King wrote:
The message
from "Simon" contains these words:

Before I go out and buy some expensive perforated copper sheet,
can anyone offer advice on improvements?

Door from an old microwave should make a nice seethrough
radio-opaque wossname.

Ooooh - lateral thinking! Nice one Skip!

A microwave oven is a good choice, because it will NOT completely block
the signal. This is because the door seals use a quarter wave
transmission line structure which means that an open circuit is
converted into a short circuit at the operating frequency. Hence they
avoid the need for metallic contacts which would become ineffective
when covered in food residues. They just need close proximity between
the door and the oven.

Mobile phones use different frequencies to microwave ovens, so the oven
door seals will attenuate but not totally block the signal. (I just
tried it with my GPRS phone on Orange - the signal dropped from 4 bars
to 1.

John

In message , Simon
writes
Hello -

Before I go out and buy some expensive perforated copper sheet, can anyone
offer advice on improvements?


Rather than getting the Faraday cage to come to you how about going to
it?
Any underground car parks nearby?

--
Bill

In message .com,
writes
A microwave oven is a good choice, because it will NOT completely block
the signal. This is because the door seals use a quarter wave
transmission line structure which means that an open circuit is
converted into a short circuit at the operating frequency. Hence they
avoid the need for metallic contacts which would become ineffective
when covered in food residues. They just need close proximity between
the door and the oven.

Mobile phones use different frequencies to microwave ovens, so the oven
door seals will attenuate but not totally block the signal. (I just
tried it with my GPRS phone on Orange - the signal dropped from 4 bars
to 1.

Didya switch the microwave on ?
`
--
geoff

Rather than trying to see in, why not put a camera (Web Cam ?) and light
bulb in the box, and bring the cables out ?

you could then have a sliding aperture to leak in as little or as much as
you want..

Nick

In article
Simon wrote:
Hello -

I'm writng some software to run on a PocketPC with a built-in GPRS phone,
and I need to test the software when the GPRS signal is weak, intermittent
or non-existent. The cheapest way to do this seems to be to build a Faraday
cage with adjustable leakiness. It needs to have some holes in it so that I
can see the screen and tap it with a stylus. Unfortunately I'm working at a
location that has excellent GPRS coverage.

I've already confirmed that a metal tin that previously contained Marks and
Spencers chocolate biscuits is 100% effective, but I can't see through it or
operate the PocketPC. I've also tried making a cage out of a single sheet of
galvanized chicken wire with 12mm square holes, held together with plastic
cable ties, with overlapped joints. This only caused a small amount of
attenuation, the PocketPC hardly noticed. I'm guessing that it failed
because the diagonals of the holes are larger than 10% of the wavelength
that GPRS uses (1800MHz ?) or because the plastic cable ties don't provide
good conductivity at the joints.

Before I go out and buy some expensive perforated copper sheet, can anyone
offer advice on improvements?

Get a large cardboard box (or old wardrobe), wrap it in kitchen foil and
sit inside it. :-)

You'll need to make very good joins betweeen the sheets of foil to make
that work.

Copper tape with conductive adhesive is ideal for this, but you had
better be sitting down when you look up the price.

Bringing a cable into an enclosure is the best way to bring in mobile
phone signals as well. When I needed to do almost exactly what you are
doing in a commercial test chamber I had to filter every signal
separately with feedthrough capacitors.

The chamber was quite impressive. They tested military vehicles in
there - even tanks - and could rotate them on a huge turntable.

John

Bill wrote:
In message , Simon
writes
Hello -

Before I go out and buy some expensive perforated copper sheet, can
anyone
offer advice on improvements?


Rather than getting the Faraday cage to come to you how about going to it?
Any underground car parks nearby?

Try placing the phone inside some chicken wire or rabbit wire...not sure
what the attenuation would be, but pretty high.

Rob Morley wrote:
In article
Simon wrote:
Hello -

I'm writng some software to run on a PocketPC with a built-in GPRS phone,
and I need to test the software when the GPRS signal is weak, intermittent
or non-existent. The cheapest way to do this seems to be to build a Faraday
cage with adjustable leakiness. It needs to have some holes in it so that I
can see the screen and tap it with a stylus. Unfortunately I'm working at a
location that has excellent GPRS coverage.

I've already confirmed that a metal tin that previously contained Marks and
Spencers chocolate biscuits is 100% effective, but I can't see through it or
operate the PocketPC. I've also tried making a cage out of a single sheet of
galvanized chicken wire with 12mm square holes, held together with plastic
cable ties, with overlapped joints. This only caused a small amount of
attenuation, the PocketPC hardly noticed. I'm guessing that it failed
because the diagonals of the holes are larger than 10% of the wavelength
that GPRS uses (1800MHz ?) or because the plastic cable ties don't provide
good conductivity at the joints.

Before I go out and buy some expensive perforated copper sheet, can anyone
offer advice on improvements?

Get a large cardboard box (or old wardrobe), wrap it in kitchen foil and
sit inside it. :-)


Right. Another thing to try is metal building lath.

This is used as a base for rendering. Its a deal smaller bore than
chicken or rabbit wire.

And its dirt cheap.

The Natural Philosopher wrote:
Right. Another thing to try is metal building lath.

This is used as a base for rendering. Its a deal smaller bore than
chicken or rabbit wire.

And its dirt cheap.

I did some work with GSM signals, our faraday cage used mesh with ~6mm
dimaond perforations.

--
Spamtrap in use
To email replace 127.0.0.1 with blueyonder dot co dot uk

Simon wrote:
Hello -

I'm writng some software to run on a PocketPC with a built-in GPRS
phone, and I need to test the software when the GPRS signal is weak,
intermittent or non-existent. The cheapest way to do this seems to be
to build a Faraday cage with adjustable leakiness. It needs to have
some holes in it so that I can see the screen and tap it with a
stylus. Unfortunately I'm working at a location that has excellent
GPRS coverage.

I've already confirmed that a metal tin that previously contained
Marks and Spencers chocolate biscuits is 100% effective, but I can't
see through it or operate the PocketPC. I've also tried making a cage
out of a single sheet of galvanized chicken wire with 12mm square
holes, held together with plastic cable ties, with overlapped joints.
This only caused a small amount of attenuation, the PocketPC hardly
noticed. I'm guessing that it failed because the diagonals of the
holes are larger than 10% of the wavelength that GPRS uses (1800MHz
?) or because the plastic cable ties don't provide good conductivity
at the joints.

Before I go out and buy some expensive perforated copper sheet, can
anyone offer advice on improvements?

Thanks

Why not control the PPC remotely using software such as SOTi Remote
Controller? Then you could szeal the PPC in the biscuit tin and have only a
single cable to the PC?

--
Darren Griffin
PocketGPSWorld - www.PocketGPSWorld.com
The Premier GPS Resource for News, Reviews and Forums

Why not open the phone up and remove the antenna. Loads of attenuation
can be achieved by that method

In article .com, Rob
writes
Why not open the phone up and remove the antenna. Loads of attenuation
can be achieved by that method


And possible PA damage!...
--
Tony Sayer

"Simon" wrote in message
...
Hello -

I'm writng some software to run on a PocketPC with a built-in GPRS phone,
and I need to test the software when the GPRS signal is weak, intermittent
or non-existent. The cheapest way to do this seems to be to build a
Faraday
cage with adjustable leakiness. It needs to have some holes in it so that
I
can see the screen and tap it with a stylus. Unfortunately I'm working at
a
location that has excellent GPRS coverage.

I've already confirmed that a metal tin that previously contained Marks
and
Spencers chocolate biscuits is 100% effective, but I can't see through it
or
operate the PocketPC. I've also tried making a cage out of a single sheet
of
galvanized chicken wire with 12mm square holes, held together with plastic
cable ties, with overlapped joints. This only caused a small amount of
attenuation, the PocketPC hardly noticed. I'm guessing that it failed
because the diagonals of the holes are larger than 10% of the wavelength
that GPRS uses (1800MHz ?) or because the plastic cable ties don't provide
good conductivity at the joints.

Before I go out and buy some expensive perforated copper sheet, can anyone
offer advice on improvements?

Thanks


I would use the tin idea with a small hole cut and connect the USB cable and
then use "active sync remote display" to control and view the screen. Easy!

Then you can chop the tin up and creat some leaks to simulate different GPRS
strength.

Paul

tony sayer wrote:

In article .com, Rob
writes

Why not open the phone up and remove the antenna. Loads of attenuation
can be achieved by that method

And possible PA damage!...

Same could apply operating it in a biscuit tin, unless you introduce
some RF absorbent lining.

So how about a dummy load connected via a length of coax into the outer
of which you cut some slots, leaky-feeder style?

--
Andy

"Skier" wrote in message
...
"Simon" wrote in message
...
Hello -

I'm writng some software to run on a PocketPC with a built-in GPRS
phone,
and I need to test the software when the GPRS signal is weak,
intermittent
or non-existent. The cheapest way to do this seems to be to build a
Faraday
cage with adjustable leakiness. It needs to have some holes in it so
that
I
can see the screen and tap it with a stylus. Unfortunately I'm working
at
a
location that has excellent GPRS coverage.

I've already confirmed that a metal tin that previously contained Marks
and
Spencers chocolate biscuits is 100% effective, but I can't see through
it
or
operate the PocketPC. I've also tried making a cage out of a single
sheet
of
galvanized chicken wire with 12mm square holes, held together with
plastic
cable ties, with overlapped joints. This only caused a small amount of
attenuation, the PocketPC hardly noticed. I'm guessing that it failed
because the diagonals of the holes are larger than 10% of the
wavelength
that GPRS uses (1800MHz ?) or because the plastic cable ties don't
provide
good conductivity at the joints.

Before I go out and buy some expensive perforated copper sheet, can
anyone
offer advice on improvements?

Thanks


I would use the tin idea with a small hole cut and connect the USB cable
and
then use "active sync remote display" to control and view the screen.
Easy!

Then you can chop the tin up and creat some leaks to simulate different
GPRS
strength.

Paul



Thanks for all the replies. I think I will seek out some finer mesh and try
the cage route again. The cage built out of 12mm mesh does decrease the
reading on the signal-strength icon, so I think smaller mesh may do the
trick.
I tried some other things, with limited success:
- I have tried disconnecting the internal antenna, but the connector is a
tiny coax connector about 2mm in diameter, which will almost certainly break
after a few repetitions.
- I don't want to activesync to the device under test, as that has an effect
on the network configuration of the device. In fact, the device stops using
GPRS altogether and sends its network traffic over the activesync cable.

declared for all the world to hear...
- I don't want to activesync to the device under test, as that has an effect
on the network configuration of the device. In fact, the device stops using
GPRS altogether and sends its network traffic over the activesync cable.

Only if you allow it to. Open activesync and un-check the "passthru"
mode.
--
Regards
Jon

Why not just download the Pocket PC remote viewing/control software from
Microsoft and operate it in the tin from a locally connected PC?

declared for all the world to
hear...
Why not just download the Pocket PC remote viewing/control software from
Microsoft and operate it in the tin from a locally connected PC?

What software is this you speak of?
--
Regards
Jon

Jon wrote:
declared for all the world to
hear...
Why not just download the Pocket PC remote viewing/control software from
Microsoft and operate it in the tin from a locally connected PC?

What software is this you speak of?

Remote Display Control for Pocket PC

http://www.microsoft.com/technet/pro...ctoys.mspx#ELD

"Simon" wrote in message
...
Hello -

I'm writng some software to run on a PocketPC with a built-in GPRS phone,
and I need to test the software when the GPRS signal is weak, intermittent
or non-existent. The cheapest way to do this seems to be to build a
Faraday
cage with adjustable leakiness. It needs to have some holes in it so that
I
can see the screen and tap it with a stylus. Unfortunately I'm working at
a
location that has excellent GPRS coverage.

I've already confirmed that a metal tin that previously contained Marks
and
Spencers chocolate biscuits is 100% effective, but I can't see through it
or
operate the PocketPC. I've also tried making a cage out of a single sheet
of
galvanized chicken wire with 12mm square holes, held together with plastic
cable ties, with overlapped joints. This only caused a small amount of
attenuation, the PocketPC hardly noticed. I'm guessing that it failed
because the diagonals of the holes are larger than 10% of the wavelength
that GPRS uses (1800MHz ?) or because the plastic cable ties don't provide
good conductivity at the joints.

Before I go out and buy some expensive perforated copper sheet, can anyone
offer advice on improvements?

Thanks



Thanks for all the replies, I have put together a webpage at
http://www.sgurr.co.uk/lundycam/faradaycage.html
describing the faraday I eventually built, based on biscuit tin and chicken
wire technology. It does block GPRS signals.