PMW1@psuvm.psu.edu (Peter M. Weiss) (07/19/90)
Please relate your experiences in using either cellular or cordless phones in a computer room, especially as it relates to any EMI that affected the operation of a computing or electronic media device. Pete Weiss, pmw1@psuvm or @vm.psu.edu Penn State U
amanda@mermaid.intercon.com (Amanda Walker) (07/21/90)
In article <9939@accuvax.nwu.edu>, PMW1@psuvm.psu.edu (Peter M. Weiss) writes: > Please relate your experiences in using either cellular or cordless > phones in a computer room, especially as it relates to any EMI that > affected the operation of a computing or electronic media device. I haven't tried one in an actual computer room, but our company regularly uses cell phones from the floors of computer trade shows, which are pretty rich in EMI from all of the computers and jury-rigged cabling. The biggest factor we've found is that it *really* helps to have a 3W radio. 1.5W units don't seem to be as good at punching out of the building to the nearest cell site. Amanda Walker <amanda@intercon.com> InterCon Systems Corporation
mrapple@uop.uop.edu (Nick Sayer) (07/21/90)
PMW1@psuvm.psu.edu (Peter M. Weiss) writes: >Please relate your experiences in using either cellular or cordless >phones in a computer room, especially as it relates to any EMI that >affected the operation of a computing or electronic media device. I have a Sun 2/170 in my living room and a cordless phone. The "magnetic media devices" I use are built like an aircraft carrier and are pretty immune to RF (as an example, my 300 MB hard disk weighs 165 lbs [70 kg or so]). However, depending on your location, it's nearly impossible to talk on the cordless when its within about six feet of the Sun. Computers use lots of square waves rich in harmonics. Really yucky. Can't comment on cellular. I am a Ham, and the highest frequency I deal with on a regular basis is 162.995 MHz. Everything from there down gets trashed pretty good unless you use an outdoor antenna (which is forbidden in my #&^@&#@^#*^*@!! condo complex) or cable (catv/cafm). Nick Sayer quack!mrapple@uop.edu 209-952-5347 (Telebit)
Dan Flak <flak@mcgp1.uucp> (07/22/90)
In article <9939@accuvax.nwu.edu> PMW1@psuvm.psu.edu (Peter M. Weiss) writes: >Please relate your experiences in using either cellular or cordless >phones in a computer room, especially as it relates to any EMI that >affected the operation of a computing or electronic media device. We have a whole office full of people using portable (cellular) phones from any where in the building to "point blank" range. So far, no problems. We have PC's, Macs, Vaxen, 3B2's, 386's ... Dan Flak - McCaw Cellular Communications Inc., 201 Elliot Ave W., Suite 105, Seattle, Wa 98119, 206-286-4355, (usenet: thebes!mcgp1!flak)
alans@hp-ptp.hp.com (Alan_Sanderson) (07/23/90)
In article <9939@accuvax.nwu.edu>, PMW1@psuvm.psu.edu (Peter M. Weiss) writes: > Please relate your experiences in using either cellular or cordless > phones in a computer room, especially as it relates to any EMI that > affected the operation of a computing or electronic media device. We have computer systems installed in telco central offices along with T1 carrier systems, D4 banks, DACS frames, and other network equipment. Some of our CEs are equipped with portable cellular phones. I have been called by the CEs from these locations, and transmission quality has been quite good. The computer equipment is FCC Class B certified for RFI emissions (computer room environment - not personal computer Class A). Alan Sanderson Hewlett-Packard AMSO alans@hpams0a.HP.COM US Snail: 1266 Kifer Rd. MS102F MaBell: 408-746-5714 Sunnyvale, CA 94086 FAX: 408-746-5571 Disclaimer: <Standard Disclaimer Applies>
alans@hp-ptp.hp.com (Alan_Sanderson) (07/23/90)
In article <9939@accuvax.nwu.edu>, PMW1@psuvm.psu.edu (Peter M. Weiss) writes: > Please relate your experiences in using either cellular or cordless > phones in a computer room, especially as it relates to any EMI that > affected the operation of a computing or electronic media device. We have computer systems installed in telco central offices along with T1 carrier systems, D4 banks, DACS frames, and other network equipment. Some of our CEs are equipped with portable cellular phones. I have been called by the CEs from these locations, and transmission quality has been quite good. The computer equipment is FCC Class B certified for RFI emissions (computer room environment - not personal computer Class A). Alan Sanderson Hewlett-Packard AMSO alans@hpams0a.HP.COM US Snail: 1266 Kifer Rd. MS102F MaBell: 408-746-5714 Sunnyvale, CA 94086 FAX: 408-746-5571 Disclaimer: <Standard Disclaimer Applies>
peter@ficc.ferranti.com (peter da silva) (07/23/90)
In article <9971@accuvax.nwu.edu> quack!mrapple@uop.uop.edu (Nick Sayer) writes: > Can't comment on cellular. I am a Ham, and the highest frequency I > deal with on a regular basis is 162.995 MHz. Everything from there > down gets trashed pretty good unless you use an outdoor antenna (which > is forbidden in my #&^@&#@^#*^*@!! condo complex) or cable (catv/cafm). Have you tried the old slinky-in-a-soup-can technique? When you want reception, "accidentally" knock the slinky off your windowsill so it hangs down over the edge. Peter da Silva. `-_-' +1 713 274 5180. 'U` <peter@ficc.ferranti.com>
huopio@lut.fi (Kauto Huopio OH5LFM) (07/24/90)
In article <10011@accuvax.nwu.edu> flak@mcgp1.uucp (Dan Flak) writes: > >Please relate your experiences in using either cellular or cordless > >phones in a computer room, especially as it relates to any EMI that > >affected the operation of a computing or electronic media device. Well, I went to a local store once and made a "RF-Reset" to an Omron cash register :) by talking at a NMT cellular phone operating around 450 MHz, with about five watts out.. The cash register wrnt totally mad, printing random numbers, but it did NOT open the cash box. NMT 900 is _nice_ !! I can take a phone from Finland and go to Switzerland and the cellular works just fine. Kauto Huopio (huopio@kannel.lut.fi) *US Mail: Kauto Huopio, Punkkerikatu 1 A 10, SF-53850 Lappeenranta, Finland * *WARNING! We have holiday season here, so be patient with my answers.. *
johns@scroff.uk.sun.com (John Slater) (07/24/90)
In article <9971@accuvax.nwu.edu>, quack!mrapple@uop.uop.edu (Nick Sayer) writes: >I have a Sun 2/170 in my living room and a cordless phone. > ... it's nearly >impossible to talk on the cordless when its within about six feet of the >Sun. The 2/170 is *old*! Our latest desktop machines (SPARCstation 1+ for instance) leak very little RF. I think they're even shielded sufficiently for use in residential areas, but I'm not certain. If you upgrade to one of our modern machines you shouldn't have any problems. I forget exactly which FCC regulations we comply with - they're not really relevant in the UK. Contact your local Sun sales office for more details. John Slater Sun Microsytems UK, Gatwick Office
darrel@prc.unisys.com (Darrel J. Van Buer) (07/25/90)
Computers and radios have an uneasy coexistence. I have had problems of mutual interference at home between a PC and my ham radio gear. Most of the time, problems are minor (slight interference with radio reception mostly), but on some bands my shortwave transmitter causes the PC to act like someone is leaning on the keyboard. They do share a power circuit and cables from both share a rats nets of wires behind my desk. Problems will vary with distance, orientation, power levels and operating frequency (since some poorly shielded wire in the computer could resonate and absorb a lot of energy). Some hams have had problems with transmitters confusing the new computerized cars. I would certainly avoid trying novel combinations of gear during important computer activities. Since power falls off rapidly with distance, you can also move away before transmitting to reduce risks. Darrel J. Van Buer, PhD; c/o Unisys; 5731 Slauson Ave, Culver City, CA 90230 (213)338-3760 KI6VY darrelj@CULV.UNISYS.COM
rpw3%rigden.wpd@sgi.com (Rob Warnock) (07/25/90)
In article <10066@accuvax.nwu.edu> alans@hp-ptp.hp.com (Alan Sanderson) writes: | FCC Class B certified for RFI emissions (computer room environment - | not personal computer Class A). Sorry, you got it backwards (typo, no doubt): FCC Part 15 Sub-Part J Class B Computing Devices is stuff used in residential environments (PC's, answering machines, smart phones, Teddy Bears that record/echo you, etc.); Class A is office/industrial. A "Computing Device" as defined and covered by Part 15/J is *anything* which contains a device for generating frequencies in excess of 10 KHz, except things covered in other FCC Parts (radios, microwave ovens, etc.), and wrist watches (which are specifically exempted in 15/J, although I would assume they have the potential to emit harmonics of 32,768 Hz, the most commonly used crystal). Rob Warnock, MS-9U/510 rpw3@sgi.com rpw3@pei.com Silicon Graphics, Inc. (415)335-1673 Protocol Engines, Inc. 2011 N. Shoreline Blvd. Mountain View, CA 94039-7311
julian@bongo.uucp (Julian Macassey) (07/26/90)
In article <10066@accuvax.nwu.edu>, alans@hp-ptp.hp.com (Alan_Sanderson) writes: > The computer equipment is > FCC Class B certified for RFI emissions (computer room environment - > not personal computer Class A). The above statement is logical but not right. Equipment meeting Class A requirements are Industrial/commercial. Class B covers domestic. The requirements for class B are far more stringent. The FCC recommends that all equipment should strive for Class B compliance. The requirements of Part 15 Subpart J have recently been revised. In reality you may find Class A equipment that causes less interference than Class B equipment. You may also find equipment that is supposed to be Class B that causes so much interference as to be unusable. I usually get flamed mercilessly for saying this sort of thing. Alas, no one ever wants to pay to challenge me at a test site. The reason for the above anomaly is that the model that passes the FCC class B test is often not the model that goes into production. All the capacitors, lumps of ferrite, bits of finger-stock etc that were used to reduce emissions and meet compliance, often fail to enter the production bill of material. Only a cynic would say this was callous cost cutting. The other thing is that peripherals are usually tested in an old IBM PC, well shielded and running with a nice slow clock. That peripheral then is sold to put in high speed poorly shielded clones. Just as a matter of interest, I have an apartment loaded with a PBX, several CPUs, and sundry radios (both receivers and transmitters). My main source of interference is a light dimmer in the apartment building next door. When are the FCC going to do something about light dimmers? Julian Macassey, n6are julian@bongo.info.com ucla-an!denwa!bongo!julian N6ARE@K6IYK (Packet Radio) n6are.ampr.org [44.16.0.81] voice (213) 653-4495
russ@unmvax.cs.unm.edu (Russ Kepler) (07/28/90)
In article <10150@accuvax.nwu.edu> julian@bongo.uucp (Julian Macassey) writes: >In article <10066@accuvax.nwu.edu>, alans@hp-ptp.hp.com >(Alan_Sanderson) writes: >[regarding 'good' class A and 'bad' class B] > The reason for the above anomaly is that the model that passes >the FCC class B test is often not the model that goes into production. >All the capacitors, lumps of ferrite, bits of finger-stock etc that >were used to reduce emissions and meet compliance, often fail to enter >the production bill of material. Only a cynic would say this was >callous cost cutting. The other thing is that peripherals are usually >tested in an old IBM PC, well shielded and running with a nice slow >clock. That peripheral then is sold to put in high speed poorly >shielded clones. This isn't always the case. In the one certification I worked on there was an intense effort to add extra shielding to the serial and parallel cables. In addition the cables were cut to the exact length to reduce the peak power radiated in those frequencies where we were radiating the most. Changing the cables or using cables with poor shielding would have removed the B compliance. But the real killer in a PC chassis is the single point ground on a lot of the cards in the cage. I've always wondered if you could DX on CW with the power switch on a PC... Russ Kepler - Basis Int'l SNAIL: 5901 Jefferson NE, Albuquerque, NM 87109 UUCP: bbx.basis.com!russ PHONE: 505-345-5232