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Author Topic: Blocking cell phone signals in theaters John Eickhof Jedi Master Film Handler Posts: 588 From: Wendell, ID USA Registered: Jan 2000 posted 01-18-2006 11:18 AM                        I helped a friend install a farday sheild on the roof and side walls in his 2 screen theatre a couple years ago, he used 1/2" galvanized steel mesh soldered together and isolated then grunded to earth. So far it works very well and he has yet to receive a complaint form ANYONE regarding loss of signal or missed calls! Plus he says He can sit and watch the film with everyone else without the rude interruption of ringers! The mesh is sandwiched in the roof system and behind the accustic drapes so it is completely hidden. Thus, no lightning threat.  |  IP: Logged Jason Miller Expert Film Handler Posts: 241 From: Little Rock, AR, Registered: Mar 2004 posted 01-18-2006 05:54 PM                    has he tested it with different carriers to see if it works on all towers? I was under the impression that a close enough tower would be able to penetrate that shield.  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 01-19-2006 10:28 AM                        At that frequency, a Faraday shield should be very good. The degree to which it is effective depends upon the per cent coverage and workmanship that you have. My guess is that this is hard to do after-the-fact. I have seen broadcast facilities with 100 Kw transmitters where the studio was encased in a Faraday shield that was 100% effective. Louis  |  IP: Logged Lyle Romer Phenomenal Film Handler Posts: 1400 From: Davie, FL, USA Registered: May 2002 posted 01-20-2006 09:52 AM                     An average building will attenuate a cell phone signal 15-20 dB. A decently put together faraday cage should get you another 50 or 60 dB. Using the low end of those estimates, you should be attenuating at least 65 dB. Cell phones (GSM) will work down to around -100 to -110 dBm. In order to have at least -110 dBm in your auditorium the exterior signal would have to be -45 dBm or stronger. This is an extremely strong signal. The strongest I've personally seen is -35 dBm a few hundred feet from the tower. Basically, as long as the tower is 1/4 mile or so away, there is very little chance that any phone will work. Even if the tower is in the parking lot, most phones probably won't work because people are sitting with them in their pockets which will further attenuate. CDMA technology phones will have different measurments but the coverage radius from a given tower is similar to GSM. It is extremely possible to do a passive cell phone blocker with a faraday cage, it's just a matter of the expense.  |  IP: Logged John Eickhof Jedi Master Film Handler Posts: 588 From: Wendell, ID USA Registered: Jan 2000 posted 01-24-2006 11:54 AM                        It's been in place for several years in a medium sized metro area (45,000 + pop ) There are at least 3 servers in town and I asked him about it and he said that he has not heard of anyone receiving a call signal inside the auditorium! He also said the local PD, EMT, & FD personnel always leave their fones with him or have their dispatch call his thru line for emergencies, and had no prblems or complaints yet!  |  IP: Logged

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