RE: Measurement below 30MHz
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: djumbdenst...@tycoint.com[SMTP:djumbdenst...@tycoint.com] > Reply To: djumbdenst...@tycoint.com > Sent: Friday, June 07, 2002 5:34 PM > To: emc-p...@majordomo.ieee.org; kcc...@hkpc.org > 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: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" > --- 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"
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: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"
RE: Measurement below 30MHz
Hello KC, The attached message leads you a web site that discusses the 20 versus 40 dB/decade problem. ANSI/NIST may/should be doing a study. Regards, Ken Hall -Original Message- From: KC CHAN [PDD] [mailto:kcc...@hkpc.org] Sent: Thursday, June 06, 2002 7:36 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" --- Begin Message --- Ken Hall asked me to make these files available on my personal area on the ARRL Web site. He considers these to be public documents, so they can be shared as needed. The following summary document also contains hyperlinks to the various files Ken shared with us earlier. http://www.arrl.org/~ehare/c63/plc/C63_Summary_11_May.pdf http://www.arrl.org/~ehare/c63/plc/C63_Summary_11_May.doc http://www.arrl.org/~ehare/c63/plc/C63_Summary_11_May.htm - Not real pretty, but good for those that cannot read .doc or .pdf files. Let me also thank Ken for the significant amount of work he put into this project. This really makes a big difference to the work of C63! 73, Ed Hare, W1RFI ARRL Lab 225 Main St Newington, CT 06111 Tel: 860-594-0318 Internet: w1...@arrl.org Web: http://www.arrl.org/tis ARRL is the National Association for Amateur Radio. It is supported by membership dues, individual contributions and the sale of publications and advertising. For more information about ARRL, go to http://www.arrl.org/news/features/inside-your-league.html. For more information about membership, go to http://www.arrl.org/join.html. Your contribution can also help support ARRL's ongoing efforts to protect Amateur spectrum. Go to https://www.arrl.org/forms/development/donations/basic/ to learn more about the ways you can support the ARRL programs and activities of most importance to you. You can help ARRL protect Amateur Radio for you and future generations to enjoy. --- End Message ---
Re: Measurement below 30MHz
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]" >To: >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"
