Re: Low signal switching
I had occasion once to look at the input relay on an NM-37. The set acted as if relay contacts were corroded -- but the sealed reed relay was fine; the problem was a cold-solder joint. Relays sealed in inert gas or vacuum should never fail due to corrosion, and there's no need to limit their small-signal rating on account of that. Of course, the days when we used to carry relay burnishers and contact cleaner in our tool boxes are past, but I am now seeing relay-cleaning routines built into the firmware of Amateur radio equipment, routines which could be emulated by actually cycling input attenuators and switches once in a while instead of leaving them long enough for contact corrosion to become a problem. Cortland 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Lightning coordination in K.20 (2000) versus GR-1089
In a message dated 4/21/2003 Marko writes: I don't have much technical to add but was wondering why you are looking into this standard. Have you customers that are asking for this requirement to be met or is it simply a planning exercise? If it's customer-driven, could you share what type of customer (ILEC, PTT, North America, European, Asian, etc.)? Hi Marko: This issue was first brought to my attention by a client that makes DSL equipment for a PTT customer in Asia. However, it is likely to eventually become a problem for compliance in Europe and South America, where the regulatory requirements typically refer to K.20. I think there may be a transition period, because many of the applicable regulations refer specifically to earlier editions of K.20. However, whenever a regulation that references K.20 is updated, it typically calls out the latest edition. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 j...@randolph-telecom.com http://www.randolph-telecom.com
RE: Lightning coordination in K.20 (2000) versus GR-1089
Joe, I don't have much technical to add but was wondering why you are looking into this standard. Have you customers that are asking for this requirement to be met or is it simply a planning exercise? If it's customer-driven, could you share what type of customer (ILEC, PTT, North America, European, Asian, etc.)? I haven't seen this standard being used at all but I'm presently focussed on North America Service Provider requirements. BTW I agree with the comments that GR-1089 compliant products have proven to be extremely robust in the real-world. Cheers, Marko From: j...@aol.com [mailto:j...@aol.com] Sent: Thursday, April 17, 2003 12:54 PM To: t...@world.std.com; emc-p...@majordomo.ieee.org Subject: Lightning coordination in K.20 (2000) versus GR-1089 Hello All: I have been studying the new 2000 edition of K.20, Resistibility of Telecommunication Equipment Installed in a Telecommunication Centre to Overvoltages and Overcurrents. There appears to be an important change from the previous edition that will have a big impact on line interface design. I would like to get some feedback on whether I am understanding this properly. The change that concerns me is that for test 2.1.2 (4000 volt surge on twisted pair phone lines), K.20 now requires that the primary protector *must* operate. If there is any kind of secondary overvoltage protection internal to the equipment under test (EUT), requirement 2.1.2 pretty much forces the EUT to contain series resistors in front of the internal protection. Otherwise, the internal protection will prevent the external primary protector from operating. The requirement for the primary protector to operate can be waived if the protection internal to the EUT itself meets the requirements for a primary protector. However, this includes passing the test of 2.1.5 with vaguely specified surges of 1000 amps per wire and (presumably) open circuit voltages of 4000 volts. I note that in Telcordia GR-1089, the requirement to coordinate with the primary protector can be waived if the EUT can survive a 10x1000 uS, 100 amp surge (clause 4.6.7.1 of the 2002 edition). This requirement is fairly easy to meet without using series resistors. I find it interesting that series resistors have never been required for compliance with GR-1089, which itself is a pretty rigorous standard, nor were they required for previous editions of K.20. Now, it appears that manufacturers must decide at the outset whether their GR-1089 compliant products might ever go into a market where K.20 compliance is required. If so, the resistors have to go in the design. The series resistors needed to pass the new K.20 requirement are not ordinary resistors. Typically, they are large, wirewound, surge tolerant, flameproof resistors with steady state ratings of several watts. Two of these per port on a high density, multiport board is a big hit on board area. Furthermore, the added resistance is very detrimental to some types of DSL transmission. In other words, this change in K.20 looks like it will have a big impact on line interface design. My questions are as follows: 1) Is my understanding of the new coordination requirement in K.20 correct? 2) Is there a simpler way to comply with the requirement other than using series resistors? 3) Has there been any industry feedback to the ITU complaining about the coordination requirement as presently written? 4) Is there evidence that the 10x1000 uS, 100 amp waiver in GR-1089 is inadequate, justifying the much more stringent waiver requirement in K.20? Any and all comments on the above would be most welcome. I'm just trying to make sense out of the new requirements. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 j...@randolph-telecom.com http://www.randolph-telecom.com 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: Low signal switching
Don, I have encountered this problem with low-level signals. It seems to vary greatly from manufacturer to manufacturer (the company we had the best results with went out of business). When the contact(s) became dirty I would run a DC current and clean it. The problem would quickly return and the only real fix was to replace the relay. One to two years of life was typical. I also would like to know a good solution. Dave Cuthbert Micron Technology From: djumbdenst...@tycoint.com [mailto:djumbdenst...@tycoint.com] Sent: Monday, April 21, 2003 11:28 AM To: emc-p...@majordomo.ieee.org Subject: Low signal switching Hello Friends, I have an application in which I would like to switch system signals on coax cables. One system is 80 to 1000 MHz, the other is 1-2 GHz. I have found coax switches by Narda, DB Products and Dow Key. Dow Key indicates that the signals should be above -20 dBm to ensure that contact resistance doesn't cause a problem. The others do not spec or address low signal issues. My branches operate at -35 dBm, 0 dBm and 50 dBm. The 2 higher values are not a problem, just the -35 dBm. Are there other companies that you are aware of that make 50 ohm coax switches that are specified to operate at low signal levels? Other ideas? Best regards, Don Umbdenstock Sensormatic 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Low signal switching
There was a thread on this some time ago and I think the consensus was that the -20 dBm limit must be a typo, or a misunderstanding by the sales dept that writes the catalog copy. if the switch is purely mechanical, the signal level shouldn't matter, except for here are some wool-gathering thoughts. If there is any kind of solid-state device in the path like a diode then there could be a lower limit to the signal that would be passed through. But also if it were a purely mechanical contact with any galvanic potential induced, that might inhibit the rf signal. -20 dBm is 87 dbuV which is about 22 mV (converting mentally) and perhaps a galvanic potential could corrupt signals at a level lower than that. Maybe someone else will have a more definitive reply. From: djumbdenst...@tycoint.com Reply-To: djumbdenst...@tycoint.com Date: Mon, 21 Apr 2003 13:27:38 -0400 To: emc-p...@majordomo.ieee.org Subject: Low signal switching Hello Friends, I have an application in which I would like to switch system signals on coax cables. One system is 80 to 1000 MHz, the other is 1-2 GHz. I have found coax switches by Narda, DB Products and Dow Key. Dow Key indicates that the signals should be above -20 dBm to ensure that contact resistance doesn't cause a problem. The others do not spec or address low signal issues. My branches operate at -35 dBm, 0 dBm and 50 dBm. The 2 higher values are not a problem, just the -35 dBm. Are there other companies that you are aware of that make 50 ohm coax switches that are specified to operate at low signal levels? Other ideas? Best regards, Don Umbdenstock Sensormatic --- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Low signal switching
Hello Friends, I have an application in which I would like to switch system signals on coax cables. One system is 80 to 1000 MHz, the other is 1-2 GHz. I have found coax switches by Narda, DB Products and Dow Key. Dow Key indicates that the signals should be above -20 dBm to ensure that contact resistance doesn't cause a problem. The others do not spec or address low signal issues. My branches operate at -35 dBm, 0 dBm and 50 dBm. The 2 higher values are not a problem, just the -35 dBm. Are there other companies that you are aware of that make 50 ohm coax switches that are specified to operate at low signal levels? Other ideas? Best regards, Don Umbdenstock Sensormatic 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: Bulk current injection method for CS101
-Original Message- From: Low, Aaron S [mailto:aaron.s@lmco.com] Sent: Thursday, April 17, 2003 1:24 PM To: emc-p...@majordomo.ieee.org Subject: Bulk current injection method for CS101 I am wondering if any of you have had experience using a current probe to inject current into a power line for a modified MIL-STD-461 CS101 test? I am trying to envision how I am going to run CS101 on a 150 Amp system without blowing up the test equipment amplifiers. I cannot use two identical transformers and two identical loads to help protect the amplifiers. Thanks Aaron Aaron S. Low Systems Engineer Naval Electronics and Surveillance Systems EP5 D5 MD45 Syracuse, NY 13221-4840 Phone: (315) 456-1203Fax: (315) 456-0509 Aaron: A current probe is a very inefficient coupler at the very low frequencies that CS101 covers. I don't think it's possible to use a current probe to do this. Using the technique described in Figure A-5 of 50.7 of MIL-STD-461E, you only need two transformers and ONE dummy load. I don't understand why you say you cannot do this. One further thing you could do is use an older, vacuum tube amplifier. These amplifiers tolerate load-impressed voltages better than newer, solid-state amplifiers. I'm not sure about how much a given amplifier will tolerate, but, as a benchmark, I have done CS101 on 80 Amp, 400 Hz powerline using a single Solar 6220 transformer and a McIntosh MC-60 (tube) amplifier. I have also done 50 Amp 400 Hz lines with a McIntosh MC-100 (solid-state) amplifier. I suggest you get a few more opinions; contact Solar Electronics and maybe Fischer Custom Components. Watch out for on/off transients; you may want to put a shorting bar across the injection transformer secondary winding terminals during turn-on turn-off. You could try to design a high-pass filter for the circuit between the amplifier output and the injection transformer. I'm assuming that your power is 400 Hz, so the CS101 test starts at 800 Hz. That might be a very interesting filter design, but anything would help. Finally, try brute force! Get a variable speed motor generator, and adjust the frequency by generator RPM. This method might carry you up to several kHz, where you could then switch over to an electronic generator protected by a more reasonable high-pass filter. Wow; what a science project! Ed Ed Price ed.pr...@cubic.com Electromagnetic Compatibility Lab Cubic Defense Systems San Diego, CA USA 858-505-2780 (Voice) 858-505-1583 (Fax) Military Avionics EMC Is Our Specialty Shake-Bake-Shock - Metrology - Reliability Analysis 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: Symbols vs. text - was EN61010-1, Symbol 14
Richard, Thank you for your ongoing comments on this situation. This issue is mixed between the technical and legal communities. In the US, there have been a number of cases lost where sufficient information was not given to the user on the equipment and the user was seriously hurt or killed. Because of this outcome, it is incumbent upon manufacturers who provide products in the US to provide proper hazard markings. This includes hazard markings on farm machinery written in both English and Spanish here. The US ANSI Z535 standards recognize the use of symbols in conjunction with the written message as the basis for US markings. This is the standard that manufacturers will be held to in the US. Certainly providing a hazard marking that combines the symbol with the written explanation begins the education process. The symbol means exactly what the language expresses. In a generation or so there will be a common understanding of the symbol. Certainly the octagonal STOP sign seems to have gained worldwide recognition, I remember when some countries used a different sign, but have now changed; many are using the English word STOP on the sign as well, altho it is not a native word in their language. I understand the frustration of international/multinational companies who are trying to provide a single product into every market but it is not yet possible without some additional effort in communicating with customers in their cultural context - including their local language. So, I am not opposed to moving toward symbols, but believe that we need to continue the language markings for some time to come. br, Pete Peter E Perkins, PE Principal Product Safety Consultant Tigard, ORe 97281-3427 503/452-1201 fone/fax p.perk...@ieee.org 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
