Hello KC, I cannot comment on the Japanese standard; I can comment on the FCC regulations. The FCC does allow 40 dB/decade below 30 MHz; they also allow a different roll-off established by measuring at 2 points along a radial. The resultant may be different than 40 dB/decade, depending on the frequency and the antenna. A basic loop antenna at 13 MHz will likely produce less than 40 dB/decade. If the antenna is wound in a field canceling manor, you might measure something greater than 40/dB per decade.
Best regards, Don Umbdenstock Tyco Safety Products Sensormatic > ---------- > From: KC CHAN [PDD][SMTP:kcc...@hkpc.org] > Reply To: KC CHAN [PDD] > Sent: Thursday, June 06, 2002 10:36 PM > To: emc-p...@majordomo.ieee.org > Subject: Measurement below 30MHz > > > 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"
