Re: conducted emissions test setup
Ed: It is advantageous when the connectding line between antenna and EUT is not in line with (or parallel to) the welded gap, but at an angle of 10, 20, 45 degrees (Fahrenheit) or somewhere in the neighborhood. It improves the NSA. I ran across that about 15 years ago, verified the improvement and had to explain the situation to visitors, i.e. if you don't want to repeat yourself, leave things as they are by nature. Greetings, Bogdan. Price, Ed wrote: There's one OATS here in San Diego which uses tack-welded sheets of stainless steel. You really need your sunglasses there! 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 Services Is Our Specialty Shake-Bake-Shock - Metrology - Reliability Analysis :-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-) -Original Message- From: Scott Douglas [SMTP:s_doug...@ecrm.com] Sent: Thursday, February 24, 2000 5:34 AM To: ken.ja...@emccompliance.com; emc-p...@ieee.org Subject: RE: conducted emissions test setup Ken, The ground plane should be non-ferrous? That is a new one to me. Are all the OATS I have been to using non-ferrous ground planes? Never really noticed that before. I thought they were all galvanized steel. Somebody please enlighten me. Scott s_doug...@ecrm.com ECRM Incorporated Tewksbury, MA USA -Original Message- From: ken.ja...@emccompliance.com [mailto:ken.ja...@emccompliance.com] Sent: Wednesday, February 23, 2000 6:22 PM To: mur...@grucad.ufsc.br; emc-p...@ieee.org Subject: Re: conducted emissions test setup Importance: Low The ground plane acts as a sink for common mode CE. Without it, you have an uncontrolled test. The ground plane should be non-ferrous. Cu or bronze or even Al will work, but you can solder to Cu and bronze, but not to Al. The ground plane is common with the green wire. The LISN must definitely be bonded to the ground plane. The analyzer is connected by virtue of the coax connection to the LISN EMI port. That is technically sufficient. The spectrum analyzer should have its power input sufficiently well-filtered to be able to share a power connection with the PC. If not, they can be fed from different circuits. The green wire should be common to both circuits. -- From: Muriel Bittencourt de Liz mur...@grucad.ufsc.br To: Lista de EMC da IEEE emc-p...@ieee.org Subject: conducted emissions test setup Date: Wed, Feb 23, 2000, 8:32 AM Hello Group, Reading CISPR 16 and CISPR 22, I had some doubts about the correct setup for doing conducted emissions testing. I'd like to know if someone can put a light on this subject. My questions are: - The ground plane is really needed? If I don't use one, my results will be wrong? Or without a ground plane I'll be testing for the worse conditions?? - The ground plane can be made of any metal? Or there are specified ones? - The ground plane must be bonded to the GND connector of my mains? (my outlet is three pins: P, N and GND) - If I understood, the ground plane will be my reference ground, right? - My testing equipment (receiver+LISN) must be bonded to this same ground plane? The ground plane is bonded to the ground connector of my mains? - I use a PC to collect the test data. Can it be feeded by the same circuit that feeds the EUT+LISN? The ground connector of the PC (the one that's in the three pin plug) should be at the same ground than the ground plane? Thanks in advance and Regards! Muriel -- 8-)8-)8-)8-)8-)8-)8-)8-)8-)8-)8-)8-)8-)8-)8-)8-)8-)8-)8-)8-)8-)8-)8-) Muriel Bittencourt de Liz, M.Sc. - EMC Engineer GRUCAD - Group for Conception Analysis of Electromagnetic Devices Santa Catarina Federal University - UFSC PO Box: 476 ZIP: 88040-900 - Florianópolis - SC - BRAZIL Phone: +55.48.331.9649 - Fax: +55.48.234.3790 e-mail: mur...@grucad.ufsc.br ICQ#: 9089332 - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Products with high power LEDs
Greetings: May I suggest that you look first on the LED output and what restrictions apply to a laser of that power, considering accessibility etc. This will give you an indications of the major problems. Apply EN60950 and EN60825 and do not use the supply with 24 V as an excuse - sorry, I should say legal leeway - to go for the cheapest approach. Bogdan. wo...@sensormatic.com wrote: Assume a business product with a high power LED for use in the EU and that it operates at 230V. It will be subject to the Low Voltage Directive, so EN60950 and EN60825-1 would apply. Now assume a similar product but it operates at 24V. The LVD would not apply in this case. What are the legal compliance requirements for the LED output? - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Temperature probe
Greetings: Several years ago I ran some tests on welded, soldered and twisted thermocouples, ten of each type. Immersed in the same liquid. As sensor I used a Fluke, two decimal places. There was no difference between welded and soldered units. The deviation of the twisted thermocouples was less than one degree among the sample and to the others. Bogdan. Ned Devine wrote: Hi, I would think a thermocouple would be OK. It should be close to +/- 1 deg. C. If you need better accuracy, try a RTD. It should be +/- 0.1 deg. C. Ned Devine Entela, Inc. Program Manager III Phone 616 248 9671 Fax 616 574 9752 e-mail ndev...@entela.com -Original Message- From: Leslie Bai [mailto:leslie_...@yahoo.com] Sent: Wednesday, October 06, 1999 2:29 PM To: emc-p...@ieee.org Subject: Temperature probe Hello, group: Seems that my question is not relavent to this group but hope someone there could help. I am looking for an ACCURATE temperature probe ( accuracy is about +/- 1 degree C from -50 to +80 degree C). It will be used to measure the microwave frequency drifting over the temperature. It will be put in a temperature chamber. Although the chamber has a temeprature display, it's not accurate as we expected (about +/-3 degree C), thus we need a more accurate probe to perform the measurement. If you have any info or similiar probe, pls kindly let me know - the brand, model, etc... Thanks in advance. Leslie http://biz.yahoo.com/prnews/991006/ca_digit_m_1.html = __ Do You Yahoo!? Bid and sell for free at http://auctions.yahoo.com - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Attachment Plugs and Power Cords
Richard: If I am not mistaken, IEC 950 refers to IEC 390. Furthermore, attachment caps and appliance inlets you should be abl;e to find in IEC 320. IMHO, you make your life unnecessirily hard on yourself if you try to interpret standards. Bogdan. WOODS, RICHARD wrote: I can find nothing in IEC 950 nor EN 60950 that defines the requirements for an attachment plug for equipment that is not permanently connected. Due to the silence of the standard, I conclude that an attachment plug is not required per the standard. Therefore, it appears that the plug wiring methods and strain relief must be per the national standards and/or electrical codes of each country. For example, UL 1950 has a national deviation that specifies the need for a plug. I conclude that it is acceptable to CE mark a product that has no plug and allow a certified plug to be attached in any of the EU member states. CE marking compliance will not be affected. I conclude that it is acceptable to replace a plug on a CE marked product with a nationally acceptable plug without affecting CE marking compliance. I understand that the power cord must be acceptable for use in the target country. Therefore, it is not possible to ship a single attached power cord to Asia, Eastern Europe, Africa and South America since the power cord may not be legal in the target country even if a national plug is attached. Are my conclusions and understandings correct? - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: FW: UL legal requirement
Greetings: When you want to apply the UL Listing or Registration Mark, you have to comply, right? The same applies to the CSA Monogram, which is a legal requirement, unless my memory is gone entirely. Otherwise you are wasting valuable electrons and time. Bogdan. Price, Ed wrote: Posted for: aimee.l.da...@us.ul.com :-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-) Ed Price ed.pr...@cubic.com Electromagnetic Compatibility Lab Cubic Defense Systems San Diego, CA. USA 619-505-2780 (Voice) 619-505-1502 (Fax) Military Avionics EMC Services Is Our Specialty Shake-Bake-Shock - Metrology - Reliability Analysis :-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-) -Original Message- From: aimee.l.da...@us.ul.com [SMTP:aimee.l.da...@us.ul.com] Sent: Monday, September 20, 1999 8:34 AM To: emc-p...@majordomo.ieee.org Subject: Re: UL legal requirement Doug and others are correct that UL cannot impose regulations on any device. Applying the UL Mark to a product is a voluntary, consumer driven choice--not law. RCIC - http://www.rcic.com Regulatory Compliance Information Center - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Amplifier for measurements above 1GHz
Greetings, May I suggest that you contact Vladan Temer of Sonoma Instrument, Tel. 707- 542-8569; FAX 707-542-1551? Excellent equipment. Bogdan. Knighten, Jim L wrote: John, Another option to consider is the HP 8449B PreAmplifier. It may have higher noise floor than Ed's suggestion below, although at 3 meters it may be sufficient, depending on antenna factors. It is a catalog item. An interesting option that I saw a couple of weeks ago in Seattle at the IEEE EMC Symposium is the HP 84125A Microwave EMI Measurement System (don't know the price). This unit spans 1-18 GHz. The sales literature indicates a sensitivity of 10-20 dB below the FCC limit in this frequency range (assuming a horn antenna and typical spectrum analyzer transducer factors (something like the HP 8593EM). If you investigate this option, please let me know what you find. Jim Dr. Jim Knightene-mail: jim.knigh...@sandiegoca.ncr.com mailto:jim.knigh...@sandiego.ncr.com Senior Consulting Engineer NCR 17095 Via del Campo San Diego, CA 92127 http://www.ncr.com http://www.ncr.com Tel: 858-485-2537 Fax: 858-485-3788 * Notice the Area Code change from 619 * -Original Message- From: Price, Ed [mailto:ed.pr...@cubic.com] Sent: Wednesday, August 25, 1999 3:41 PM To: 'John Cronin'; emc-p...@ieee.org Subject:RE: Amplifier for measurements above 1GHz John: So you need another 10dB of gain between 1 5 GHz. I have used Miteq low-noise preamps in the past, but I bought octave-band models and I paid a lot extra for absolute lowest noise figure with about 35dB of gain. I suggest you call Miteq (get the noise figure of your spectrum analyzer first) and see what combinations they recommend. You might need only a 1dB noise figure, with about 20dB of gain, which may mean they have one unit that can span the frequency range. Site at: http://www.miteq.com :-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-) Ed Price ed.pr...@cubic.com Electromagnetic Compatibility Lab Cubic Defense Systems San Diego, CA. USA 619-505-2780 (Voice) 619-505-1502 (Fax) Military Avionics EMC Services Is Our Specialty Shake-Bake-Shock - Metrology - Reliability Analysis :-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-) -Original Message- From: John Cronin [SMTP:croni...@hotmail.com] Sent: Wednesday, August 25, 1999 2:50 PM To: emc-p...@ieee.org Subject: Amplifier for measurements above 1GHz I am hoping to purchase a 1 to 5 Ghz amplifier to be used in conjunction with a spectrum analyzer to measure emissions at 3m to FCC requirements. With a 1 MHz bandwidth into a HP microwave analyzer we can only currently measure at 1m. Can we get away with measurements at 1m? Can anyone recommend a low cost microwave amplifier that is suitable for the task? Thanks in anticipation of your response. John Cronin __ Get Your Private, Free Email at http://www.hotmail.com - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion
Re: Fault Testing Electrolytic Capacitors
Bob: My ha'penny's worth: What about increasing the voltage rating of the subject electrolytics? This may be expensive, requiring costly capacitors. Something el cheapo: what about a fuse on the input side of the cap? Are the electrolytics by-passed with capacitors about 0.1 uF or less, with short, wide leads? This would help with the higher frequency currents. Please let me know what the final verdict will be. Bogdan. Bob Designer wrote: A company I represent has a problem with their switching power supply. A single point failure in the regulator can cause the output voltage to rise higher than the voltage ratings of the electrolytic capacitors. As a result, the capacitors are overstressed and fail in a variety of ways depending upon the capacitor venting method. Sometimes the vent will pop and thats the end of it. Other times, the capacitor will overheat and expel ethylene glycol in the form of vapor or liquid. In some cases, the conductive fluid will bridge the primary circuits to earth causing a failure of the hypot test. This is unacceptable for IEC950 compliance. I have spoken to several power supply designers and they inform me that it is common practice not to provide overvoltage protection. Of course, if that is true, then there appears to be a lot of power supplies in the world, perhaps including the one in my pc, that may or may not pass the fault testing of IEC950 depending on how the electrolytic capacitors fail. Obviously, my client does not want the extra cost of adding overvoltage protection when it appears that others dont do it. I would appreciate your comments concerning this failure mode, the use or non-use of protective circuits, and passing the IEC950 fault test if a protective circuit is not used. Regards, Bob _ Do You Yahoo!? Free instant messaging and more at http://messenger.yahoo.com - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Immunity requirements for equiment sold to research labs.
Chaz: To state the obvious first, I know of no EMC standard which refers specifically to laboratory equipment. However, I would think that talking to your customers about EMC may result in the most sensible approach. Aside from those who never heard of EMC, you may find customers who perform very sensitive experiments where even compliance with Class B will overload their input amplifiers etc. As a general statement I would venture to say that you should strive to stay below Class B (CISPR22 of course) by a viable margin, 6dB or more. I would also talk to customers to find out what kind of equipment the use. This may show that even 10 V/m immunity of your equipment may not be enough. Regards, Bogdan. Grasso, Charles (Chaz) wrote: Can anyone tell me what the Immunity requirements for equiment sold to research labs might be. Charles Grasso Advisory Engineer StorageTek 2270Sth 88th Street Louisville CO 80027 M/S 4247. Tel:303-673-2908 Fax:303-661-7115 email:gra...@louisville.stortek.com Web Site: http://www.ewh.ieee.org/r5/denver/rockymountainemc/ - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Precompliance Testing
May I add a note of caution: It may be worthwhile to check the permissible loading of the roof, especially when you are in the Southwest where roofs are mostly for shade and a few drops of rain. I guess that you don't want to appear suddenly in the conference room below Bogdan. Gary McInturff wrote: I'll agree with Brent, and others, the headaches of a metal room or the metal studs et al, in a building are going to make you pull your hair out. But there is an alternative to the parking lot. You may want to consider the roof. The ground reference can be put up there as well, especially if you are doing pre-compliance stuff. You don't have to give up parking space - which is sure to irate somebody. The roof gets a little hot, but that only gives you the opportunity to work in your cutoffs, and showing up to a meeting with the suits dressed like this is always good for a laugh! Gary -Original Message- From: Brent DeWitt [SMTP:bdew...@ix.netcom.com] Sent: Friday, April 23, 1999 7:12 PM To: Allen Tudor; emc-p...@ieee.org Subject:RE: Precompliance Testing Allen, From bunches of years of designing and using sites, what I would suggest is, IMHO, use the money to reserve a large space in the parking lot free of obstacles. Current construction techniques in buildings use lots of steel 2x4s for the walls and there will likely be steel in the floor above you. All of these contribute to resonances in the emissions measurements that are far too difficult to want to deal with. The best way to do radiated measurements is to be a minimalist. Get as far away from any structure as you can, put down a simple hardware cloth ground plane and throw a nylon tent over the product if it rains. Best regards, Brent DeWitt Datex-Ohmeda Medical Louisville, CO -Original Message- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Allen Tudor Sent: Friday, April 23, 1999 1:27 PM To: emc-p...@ieee.org Subject: Precompliance Testing Our division is in the process of constructing a new building. I have been told that I will be given a room in which to make pre-compliance radiated emissions measurements. However, ferrite tiles or cones are out of the question (I have been told that I can hang chicken-wire on the walls if I want to). Even though I am restricted in how much money can be spent, I have the luxury of designing in features as the building is being constructed. At a bare minimum, I think we should lay sheet metal or grid-wire on the floor after the concrete is poured. This ground plane should be grounded at each corner by ground rods. I am thinking that if there is no steel framework near the room, this may provide fairly good results. I would appreciate any recommendations on other cheap features that I can design in while the building is under construction. Also, what is the minimum size the room should be? How about power wiring in the walls and in the ceiling. Should any measures be taken to prevent radiated energy from coupling into power wiring? Perfection is not the key issue here: repeatability is. We have a local certified lab that I can compare my measurements with. Once the room is complete, I can repeat my measurements at the certified lab and develop the necessary correction factors. By the way, my product is dc powered shelf-level telecom equipment. Again, any advice will be appreciated. Thanks in advance. Allen Tudor, Compliance Engineer PairGain Technologies tel: (919)875-3382 2431-153 Spring Forest Rd. fax: (919)876-1817 Raleigh, NC 27615 email: allen_tu...@pairgain.com - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line:
Re: Rodents, part II
Lou: In better times I used to live and wok in Huntsville, AL, and met a few of them moccassins , however yours must have been especially long if it could strike accross the road, i.e. about 20 to 30 ft in your case. The longest critter of this kind I ever encountered was about 6 - 7 ft long and I helped him cross the road at night by using my leather jacket like a broom, and I was of course out of this jacket. Finally: instead of RG223 I would recommend piano wire - works faster. Regards, Bogdan. Lou Gnecco wrote: Brent, When i worked for NASA we also had water moccasins. They liked to get in the cable trays and snuggle up next to the RG-9 coax cables, which were indistinguishable from them. Those snakes were highly poisonous and very aggressive. They were also BIG. they could strike clear across the ( 1 lane) road, and if you threw rocks at them, they would actually chase you. If you ever run into this problem, one way to get them is with a CO2 fire extiguisher. they hate the cold and it drives them off. Another way is to take a 10 ft piece of conduit, run a length of RG-223 thru it, leaving a loop at the far end. Then you ease up to the snake, slip the loop over its head and PULL, decapitating it. This takes nerve, because to do this you must be well within the snake's striking distance. I never did it, but I have stood there (aghast) and watched one of our technicians do it, several times. Do not try this at home. Lou At 03:47 PM 5/3/99 -0600, you wrote: Has anyone else noticed how rodents (Prairie dogs, squirrels, etc.) just _love_ polyethylene? They must think it's candy. Prairie dogs have chewed all the way to the center conductor of the coax at a couple of sites I've run and back in my Forest Service radio tech days we had to use C wire impregnated with a chemical that made it taste bad to the squirrels or they would chew it up. Sorta EMC related... Brent -Original Message- From: ed.pr...@cubic.com [mailto:ed.pr...@cubic.com] snip 7. Ants and rodents. (You are only one step short of a picnic.) Ed - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Doubt on Measuring with Spectrum Analyser
Cortland: I think that the 10 dB attenuator would have done better service when connected directly at the antenna by improving the match. Two 6 dB attenuators should render better service, one at the antenna, the other directly at the amplifier. Ferrite clamp-on beads placed at irregular intervals on the cable help reduce common mode inputs to the amplifier and from my experience also do help (obviously). Regards, Bogdan. Cortland Richmond wrote: Jim, The 8447D seems a fine amplifier of its type. I've used another make that was MUCH more susceptible to intermodulation and distortion. But it is broadband, and it does amplify the mega-signals as well as the low level ones you want to see. So, even if the _amplifier_ does not crunch, you may find the analyzer front-end being overloaded by strong (and add 25 dB!) signals. Anything you do that raises the signal level at the analyzer may have this effect. I once bought -- out of my own pocket -- a 9913 type coax to replace RG214 on a ten-meter site. The resulting increase in signal raised IM so much that mixing products actually obscured the signals we wished to see. Was THAT a surprise (ever pulled cable on a 10 meter site?). The solution was a 10 dB attenuator on the preamp. However, if you are willing to use the HP PREselector, which can give 20 dB of gain on its own, you can eliminate the 8447D, and when you do this, the odds are much in favor of being able to see low level signals you could not before. Of course, you need a low-loss coax OR enough gain at the antenna to overcome the coax loss. This is pretty much a requirement anyway because given the loss in 30 meters or so of cable, the noise floor at an analyzer is approaching the limit around a GHz unless you can reduce coax loss. That's why I changed coax. It's worse at a 30 meter site. Some folks go rigid coax all the way to the antenna pedestal, and it is a good investment. If you did use an amplifier at the antenna, you would have to take its thermal response into account, provide power, and keep an eye on the gain. Low loss coax, on the other hand. is much simpler to deal with. Now, as to your particular setup... if you mean to do quick, close pretests, then you will probably be fairly happy with a 1 meter test distance (given a small EUT). It may happen that a fixed antenna height will do for you. At this distance, you could probably use RG-58 and not notice a problem, and the 8447D preamplifier might not even be needed except with low-gain loops and probes -- it is handy for those. A 1 meter scan can be very useful. But if you need to sweep the antenna height -- the FCC wants 1 meter to 4 meter heights -- you NEED a mast with remote elevation control. You CAN build these, and you can buy them. It's a lot easier to buy them. If you plan on sometime doing automated testing, make sure it reports height in a form you will be able to use. However, if you have the chance to get a real open air test site or a real anechoic chamber, I recommend them, the latter most of all. Getting rid of ambient signals for radiated testing is a major step forward and makes automating testing later much, much easier. Having readings you can measure up against those of your supplier (or customer!) is a Good Thing. (Don't expect an _exact_ match, of course.) Cheers, Cortland == Original Message Follows Date: 28-Sep-98 12:25:25 MsgID: 1064-12413 ToID: 72146,373 From: Jim Eichner INTERNET:jeich...@statpower.com Subj: RE: Doubt on Measuring with Spectrum Analyser Chrg: $0.00 Imp: Norm Sens: StdReceipt: NoParts: 1 You wrote: Although it is preached everywhere, a low-gain amplifier at the antenna end of a site is a good way to begin,but rarely done. Most folks, it seems, opt for inexpensive coax and a high-gain, broadband preamplifier, which invites such problems. However, that is properly another thread.) We are in the process of figuring out what is involved in setting up a basic radiated emissions measurement capability for ourselves, having gone as far as we can using near-field probes, RF clamp-on current probes, etc. We intend to buy a pair of antennae, a tripod, a pre-amp, and some cable, and hook it up to our existing SA. Your comments re pre-amp placement are familiar to me, but I'm not sure about the low-gain part of it. What we have had recommended to us is the HP 8447D, which has 20dB gain across the band (30M-1GHz) we're interested in. Is this too high for use at the antenna end of the system? If so, why? Also, I thought putting the pre-amp at the antenna end would let us use cheap co-ax, since the S-N issue would be dealt with by having a stronger signal from the antenna. Am I missing something? Also, it sounds from your e-mail as if there is an option to the use of a broad-band pre-amp. What would that be? Thanks in advance for your help.
Re: EN 55022 vs. Telecommunications -48Vdc DC Powered Equipment, Conducted Emissions AC side or DC side?
Don: My suggestion would be to test at -48 V and also on the ac-side of any converter that your company suggest as appropriate. Make sure that those converters are listed in the user's information, accompanied by a statement saying something like compliance with Class B of CISPR 22 can not be guaranteed when used with different converters. As you can see, I did not use the word is so there should be no problems with definitions. Regards, Bogdan. Donald Kimball wrote: I work for Qualcomm, and we EMC test -48Vdc powered telecommunications equipment, especially cellular and PCS base stations. The -48Vdc power is usually shared with other equipment at the same location (eg. an Alcatel Switch, Cisco Router, etc.) We have always tested for conducted emissions on DC side of the power line, since we do not control the AC to DC power converter, and we share the DC power with other equipment. Recently, we integrated another vendor's E1 inverse multiplexer into our base station controller racks. The vendor claimed CE mark compliance and sent us a test report. This equipment is powered by -48Vdc, but they tested for conducted emissions on the AC side of the AC to DC power supply that powered the E1 inverse multiplexer. When questioned, they said that the test facility told them they must test on the AC side of the line, and not the DC side of the line. The test facility said they would not issue a declaration of conformity based on testing the DC side of the power line. In fact, they went through several AC to DC power supplies before they found a power supply that was EN 55022 compliant by itself. This makes no sense, since the DC power is shared, and the choice of AC to DC power supply cannot be controlled by Qualcomm. Moreover, a well chosen AC to DC power supply can filter out the noise on the DC side of the line. In fact, one version of the inverse multiplexer fails on the DC side of the power line, but passes on the AC side of the line. If the emissions on the DC side of the power line are compliant with EN 55022 Class A limits, the those same emissions should be below the limit on the AC side. What is the correct answer in this case? Do you test the AC side or the DC side? Don Kimball - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
