KC, Allow me to make one additional comment regarding your final statement. You asked ". . . which one should I use?"
The FCC will never have a problem with you using linear (20 dB/decade) roll-off. This is more restrictive than is sometimes called for. They allow the use of 40 dB/decade below 30 MHz. You will not have a rejection of an application for using a provision that is allowed. Similarly, if you choose, the FCC allows you to use other roll-off factors as long as you use at least 2 points to establish the roll-off and provide the calculation that showed how you arrived at your results. So which to use? That is up to you. Personally, I generally use 2 points and provide the roll-off calculated. Good luck, Don Umbdenstock > ---------- > From: [email protected][SMTP:[email protected]] > Reply To: [email protected] > Sent: Friday, June 07, 2002 5:34 PM > To: [email protected]; [email protected] > Subject: RE: Measurement below 30MHz > > > 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:[email protected]] > > Reply To: KC CHAN [PDD] > > Sent: Thursday, June 06, 2002 10:36 PM > > To: [email protected] > > 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: > > [email protected] > > with the single line: > > unsubscribe emc-pstc > > > > For help, send mail to the list administrators: > > Ron Pickard: [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: > > 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: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: [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: > 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: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [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: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
