Greetings all, Sorry for the late reply - summer :o) I have done some work with cell phones and have found that certain digital bands cause much greater interference than others. Specifically, I had reason to measure emissions of phones from several well known but unnamed dual band and tri-band cell phone brands. Across brands, a certain mode of digital operation caused the phones to be about 10-15 dB above the class A limits from 40 MHz all the way to 1 GHz (isolated, but MANY frequencies - not continuous broadband). Granted, this pales by 20+dB in contrast to the fundamental, but I still found it amazing that a 4 inch long device could emit those levels of RF at frequencies around 40 MHz. I forget which band (normal 800 MHz digital or 1800(?) MHz GSM) caused the most interference, but the operation in the other band & analog was dead quiet except for the transmitter related signals (very few centered about the fundamental). For some of the phones I tested, there were setup options that allowed modes to be locked out if one knew the codes.
BTW in case anyone is wondering, these levels are acceptable for cell phones. Perhaps this contractor's phone was only capable of (or software limited to) operation in the 'quiet' mode of operation above? (or just happened to be in that mode of operation at the time of "test"?) This might constitute an "approved for CO use" phone. Regardless, every piece of CO equipment (at least owned by the RBOC) should be immune to 9.8 or so V/m signals and any exceptions should be known by the CO administrators as such information is included in a NEBS report (Immunity to 10V/m is a conditional requirement only - I believe 1.7 V/m is the Requirement but any malfunctions from 1.7 < level < 10 V/m must be noted in the report with frequencies, symptoms, and minimum susceptibility levels). If the phone was tested, it could have been checked to ensure that it was not emitting high levels of RF at these sensitive frequencies - basically ensuring that the maximum ambient for the equipment in the CO was not exceeded. Any competetive co-located equipment is up in the air for immunity, but I'm sure the Bells don't care to take precautionary measures on those (realistically, at least - I'm sure it's not policy but they certainly don't ask for RF immunity data on such equipment). Best regards, Dave Heald "Price, Ed" wrote: > > A few days ago, I got a little involved in a Usenet discussion about a > contractor using his cell phone within a Telco CO while working on equipment > repairs / upgrades. My position was that I didn't think this was a good > idea, since I know that a cell phone will create about 5 to 10 V/M at about > 2 meters distance. > > The contractor made a statement that his cell phone had to be submitted to > the "CO switching engineer", who, after doing some kind of measurements, > allowed the use of the phone within the CO. I asked the contractor what kind > of criteria the "switching engineer" used to evaluate the cell phone. The > contractor replied (not very clearly) that the "switching engineer" used a > "network analyzer with a plug-in S-parameter head." > > Well, I'm not sure if the contractor got the mushroom treatment, as that > doesn't sound like what you need to evaluate RF field strength! But, what > criteria should have been applied, and are there approved cell phones for > such instances? > > Regards, > > Ed > > > Ed Price ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: [email protected] Dave Heald [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.rcic.com/ click on "Virtual Conference Hall,"
