No one seems to be answering this, so I will take a stab at it. But this is only technical aspects, not a policy response. At 13 MHz (11.5 m tuned dipole) a real measurement antenna (one which draws power from the Poynting vector impinging upon it) will not be measuring in the far field. Further, since a 13 MHz tuned dipole would be a special build, you likely will be using either an electrically short whip or loop. Since the VDE used to require the loop below 30 MHz, it is most likely a commercial EMI test facility would have the loop. The question of scaling depends on the electrical size of the emitter and your distance from the emitter. The easiest case is if you are in the far field of the emitter, which is almost certainly the case for an RFID operating at 13 MHz. Then the field will scale linearly with distance (20 dB per decade). If you are somehow in the near field of a small loop, the magnetic field (what you measure with the loop) decreases with the cube of the distance as long as your separation from the loop is large relative to the loop dimensions which is certainly the case for an RFID at 3 meters.
---------- >From: "KC CHAN [PDD]" <kcc...@hkpc.org> >To: <emc-p...@majordomo.ieee.org> >Subject: Measurement below 30MHz >Date: Thu, Jun 6, 2002, 9:36 PM > > > To all > > I just came across a Japanese standard about a RFID product at 13.5 MHZ, it > says that measurement of FCC from 30m to 3m will need to take the 20dB > conversion(ie 20dB/decade) into account. > > But I found a statement from FCC part 15.31(f)(2) that at frequency below > 30 MHZ, 40/decade extrapolation factor shall be used. > > I just want to clarify which we should use for measurement below 30MHz, > 20dB/decade or 40/decade? > > Thank you > KC Chan > > > ------------------------------------------- > 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 > > All emc-pstc postings are archived and searchable on the web at: > http://ieeepstc.mindcruiser.com/ > Click on "browse" and then "emc-pstc mailing list" > ------------------------------------------- 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 All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
