Maker Pro
Maker Pro

Simple screened room integrity test

R

Richard Henry

Jan 1, 1970
0
We recently purchased a used screened room and had it installed in our
new spaces. Is there a simple test to see how well it has been put
together?
 
V

Vladimir Vassilevsky

Jan 1, 1970
0
Richard said:
We recently purchased a used screened room and had it installed in our
new spaces. Is there a simple test to see how well it has been put
together?

Quick test: there should be no reception of cellular and FM/AM/TV
broadcast inside the room if the door is closed. Any reception indicates
a leak.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com
 
J

Joerg

Jan 1, 1970
0
Richard said:
We recently purchased a used screened room and had it installed in our
new spaces. Is there a simple test to see how well it has been put
together?

Yes, Vladimir gave the right hint. Take an AM/FM radio, see which
stations are strongest (on AM that's usually Rush Limbaugh...), go
inside. Then walk around the perimeter of that room. Since you bought a
screen room I assume you have a spectrum analyzer. Put it in the middle
in a shielded box. Seriously, I had a Agilent analyzer spew so much junk
from its LCD that it almost made me sick. Now connect a coax long enough
to reach the corners. Plug in the mid-size EMCO near-field H-probe and
sniff along the seams and especially the door.

Oh, and do _not_ leave the key in the outside of the door lock. There
are usually no phones inside and your cell phone won't do you any good
after you hear the thud of that big door.
 
V

Vladimir Vassilevsky

Jan 1, 1970
0
Joerg said:
Seriously, I had a Agilent analyzer spew so much junk
from its LCD that it almost made me sick.

Indeed. The electromagnetic noise generated by the measurement equipment
itself is very annoying. It is good to have all analysers outside of the
room.

BTW, I have seen some smart people who installed the fluorescent
lighting with the active ballasts inside of the EMC chamber.
Oh, and do _not_ leave the key in the outside of the door lock. There
are usually no phones inside and your cell phone won't do you any good
after you hear the thud of that big door.

:) It is warm and quiet. When doing the EMC measurements, I am always
thinking about taking a nap in the chamber. It is difficult to resist
the temptation during the long wideband sweeps...


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com
 
J

Joel Koltner

Jan 1, 1970
0
Joerg said:
Oh, and do _not_ leave the key in the outside of the door lock. There are
usually no phones inside and your cell phone won't do you any good after you
hear the thud of that big door.

Really? Our screen rooms have a phone (going through a filtered jack) and
Ethernet (going through a fiber-optic converter); I figured this was quite
commonplace...
 
J

Joerg

Jan 1, 1970
0
Vladimir said:
Indeed. The electromagnetic noise generated by the measurement equipment
itself is very annoying. It is good to have all analysers outside of the
room.

Use the old stuff that was designed by guys who really knew what they
were doing.

BTW, I have seen some smart people who installed the fluorescent
lighting with the active ballasts inside of the EMC chamber.

Medieval folks had their version of water boarding for those guys: Put
them in a cage, dunk them into the moat around the fortress a couple of
times, then ask them whether they'd do it again. If they say yes, dunk
again ...

:) It is warm and quiet. When doing the EMC measurements, I am always
thinking about taking a nap in the chamber. It is difficult to resist
the temptation during the long wideband sweeps...

Can't do that. Finding a consultant snoring away would not be a great
motivator. But I did once funnel a piece of wire through one of the
ports and plugged the coax inside into my EMC receiver so it wasn't so
eerily quite in there. Picked up the Don Cossack Choir on shortwave,
when even Radio Moscow would stop their dreaded propaganda. Some of the
best a capella pieces ever.
 
J

Joerg

Jan 1, 1970
0
Joel said:
Really? Our screen rooms have a phone (going through a filtered jack) and
Ethernet (going through a fiber-optic converter); I figured this was quite
commonplace...

Oh, then you must be very young. In the olden days we even had to make
our own electricity :)))

But really, the screen rooms at most of my clients are rather spartan. A
bare plywood floor is considered luxurious.
 
D

Don Bowey

Jan 1, 1970
0
We recently purchased a used screened room and had it installed in our
new spaces. Is there a simple test to see how well it has been put
together?

Go into the room and try to use a TX or RX in the frequency range you expect
to use it.
 
D

Don Bowey

Jan 1, 1970
0
Quick test: there should be no reception of cellular and FM/AM/TV
broadcast inside the room if the door is closed. Any reception indicates
a leak.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

I've never seen a perfect screened room; there was always some leakage. The
best I ever saw was at an airbase with Search Radar and a variety of HF
through VHF radios.... Zinc wall, Ceiling and door panels. Double finger
stock on door, and no windows. All antenna coaxes entered via a well
shielded box that had separate containments for the filters for each
antenna. It was very good, but....
 
R

RST Engineering \(jw\)

Jan 1, 1970
0
The best I ever used was in the microwave lab at Teledyne Ryan Aero in San
Diego. DOUBLE solid zinc walls & doors, brass finger stock coming AND going
on the doors, air filtered in through double tightly woven brass wool, ...
DAMN but I lust for that room.

THen again, we were building stuff in there that we would later be throwing
at the moon, so it had to be absolutely perfect.

Jim
 
R

Richard Henry

Jan 1, 1970
0
The best I ever used was in the microwave lab at Teledyne Ryan Aero in San
Diego.  DOUBLE solid zinc walls & doors, brass finger stock coming AND going
on the doors, air filtered in through double tightly woven brass wool, ...
DAMN but I lust for that room.

THen again, we were building stuff in there that we would later be throwing
at the moon, so it had to be absolutely perfect.

Jim

Ours isn't nearly that good. It has what looks like copper window
screen all around, so you can breathe and talk through the walls no
problem. The door is solid metal with copper finger stock all around
and the power passes through filter modules. I haven't got inside yet
to do any testing - the area is roped off while cubicles are being
assembled in the surrounding open area. Once I get in, I intend to do
the cell phone test described in theis thread and haul in a scope to
look at the noise of the lights.
 
V

Vladimir Vassilevsky

Jan 1, 1970
0
Don said:
I've never seen a perfect screened room; there was always some leakage.

It takes a lot of effort to drop all leakages at all bands to the noise
floor of the analyser. There are the test chambers like that at the big
companies I worked for; I can only imagine how much did it cost.

However what is really required that the leakages should be at least
10dB below the EMC limits that you are after. This implies no reception
of cellular or AM/FM/TV.
best I ever saw was at an airbase with Search Radar and a variety of HF
through VHF radios....

Best I ever saw was the 25 x 15 x 100 meters hall for the indoor
experiments on the radar antennas. It was a perfectly shielded building
inside the other building. That was back in the USSR. In our days, they
couldn't find better use for this chamber then giving it for rent as a
warehouse.
Zinc wall, Ceiling and door panels. Double finger
stock on door, and no windows.

How could be any windows in the schreened room?
All antenna coaxes entered via a well
shielded box that had separate containments for the filters for each
antenna. It was very good, but....

Fixing all leaks requires the special equipment and a lot of work. It is
very costly, too.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com
 
R

Richard Henry

Jan 1, 1970
0
I've never seen a perfect screened room; there was always some leakage.  The
best I ever saw was at an airbase with Search Radar and a variety of HF
through VHF radios.... Zinc wall, Ceiling and door panels.  Double finger
stock on door, and no windows.  All antenna coaxes entered via a well
shielded box that had separate containments for the filters for each
antenna.  It was very good, but....

We were selling some displays to a company making USN shipboard
radars. They had huge screened rooms. They also had a different
attitude about some other things. At the first engineering meeting
there, they asked us hom much cooling water we would need.
 
M

Mark

Jan 1, 1970
0
We were selling some displays to a company making USN shipboard
radars.  They had huge screened rooms.  They also had a different
attitude about some other things.  At the first engineering meeting
there, they asked us hom much cooling water we would need.- Hide quoted text -

- Show quoted text -

you don't want to operate a transmiter inside a screen room..

think about where the power goes.

Mark
 
J

Jim Thompson

Jan 1, 1970
0
[snip]
you don't want to operate a transmiter inside a screen room..

think about where the power goes.

Mark

Where DOES it go ?:)

...Jim Thompson
 
J

Joel Koltner

Jan 1, 1970
0
"you don't want to operate a transmiter inside a screen room.."

Sure you do, if you hook up an appropriate dummy load with a reasonably low
VSWR. We've got some 500W dummy loads around that make nice little space
heaters...
 
T

**THE-RFI-EMI-GUY**

Jan 1, 1970
0
Jim said:
[snip]

you don't want to operate a transmiter inside a screen room..

think about where the power goes.

Mark

Where DOES it go ?:)

...Jim Thompson
Into the DUMMY load hopefully. But, if you have an antenna hooked up,
guess who/whats the dummy!

--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©

"Treason doth never prosper: what's the reason?
For if it prosper, none dare call it treason."

"Follow The Money" ;-P
 
B

Barry Lennox

Jan 1, 1970
0
We recently purchased a used screened room and had it installed in our
new spaces. Is there a simple test to see how well it has been put
together?

Years ago I helped with the commissioning of a couple of Belling-Lee
rooms. These were used to stop emitters getting out, so only about 3
freqs were of interest. The usual tests were to use a Spec An outside
to see the ambient environment, then take them inside to verify the
atttenuation. This was an HP141 type, some of the newer one generate
significant internal noise that can screw up your results.

Then we fired up the emitters inside to verify that they were
sufficently attenuated outside.

The Belling-Lee engineer also mentioned that one of his clients (UK
MOD ?) used a high-power sweep oscillator inside the room, while
monitoring outside.

The biggest problems were torquing down the panels evenly and the door
fingerstock being adjusted correctly.This took about 2 days to get it
near-perfect. Unfortunately, these items require periodic checking
throughout the room's life, as they do shift with time and use.

Barry
 
D

Don Bowey

Jan 1, 1970
0
you don't want to operate a transmiter inside a screen room..

think about where the power goes.

Mark

I used a kW transmitter in the room I described before. The power went out
the coax to the antenna of choice.

Where else would it go?
 
P

Paul Burke

Jan 1, 1970
0
Richard Henry

A colleague was involved in installing a Faraday cage for emc testing.
When they'd finished, the boss came to look at it. Just after they shut
the door, his mobile phone rang...
 
Top