I read in !emc-pstc that Ken Javor <[email protected]> wrote (in <20011029005000.JIZA629.femail8.sdc1.sfba.home.com@[65.11.150.27]>) about 'CISPR 13, EN 55013', on Sun, 28 Oct 2001: >No connected cables. It was clearly a radiated test.
Your friend should ask the test-house to say **which clause in which edition of EN55013** the results relate to. >Here is what we >worked out so far, but it seems rather bizarre so I was looking for an >alternative explanation: > >It is an antenna induced limit like MIL-I-6181, but what throws me is the >arcane way (I think) they determine the antenna factor as they build their >antenna-induced limit. > >I'm not saying this is correct, but this is what my NASA colleague and I >worked out. They show a theoretical 3 m site attenuation not in terms of >straight loss between transmit antenna power input and receive antenna power >output but as the dBpW available from the receive antenna when immersed in >the field of a transmit antenna driven to generate 100 uV/m. The receive >antenna is a tuned dipole above 80 MHz, and fixed at the 80 MHz length below >80 MHz. They plot the dBpW available from that dipole as a function of >frequency (30 - 1000 MHz) given height scans of 1 - 4 m. Then they show an >antenna-induced limit in terms of dBpW measured at the receiver from the EUT >as a source. The version of EN 55013 I had was CISPR 13 - 1975. What I >want to know is if this admittedly bizarre explanation is correct. If it >is, why do they do it like that? And if it isn't, how do I read a dBpW vs. >frequency graph? The standard has changed a very great deal since 1975. I have the 1997 issue of BS EN 50013, which incorporates four amendments to the 1990 edition, and I'm not certain that this is the latest issue. It is, however, the current issue. It deviates quite a bit from CISPR13, I think. 'Electronic organs' are classified as 'associated equipment' in the standard. The method of measurement is described in clause 5.6 and the limits are given in Table 4. ****The limits apply only from 30 to 300 MHz, and only to emissions on external cables****. They are: Quasi-peak: 45 dB(pW) at 30 MHz, increasing linearly with frequency to 55 dB (pW) at 300 MHz; Average: 35 dB(pW) at 30 MHz, increasing linearly with frequency to 45 dB (pW) at 300 MHz. But the test-house seems to have applied clause 5.4 in the absence of any external cables. The site attenuation is to be measured normally and not by the method you describe. I think that 5.4 does not apply to 'associat3d equipment', because 5.6 has 'associated equipment' explicitly in the clause title. But this is not 100% clear; the applicable measurement clause(s?) should be stated in Table 4. This standard and EN55020 are notoriously badly drafted. If this point has not been dealt with already, I will try to get it fixed, together with the fact that the method of calculating the results in dB(pW) from the measurements in 5.6 is not stated! Please come back with further questions if necessary. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Eat mink and be dreary! ------------------------------------------- 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: No longer online until our new server is brought online and the old messages are imported into the new server.
