Re: Free Space Antenna Factor
In message <23938758.1204751250030.javamail.r...@elwamui-hound.atl.sa.earthlink.net> , dated Wed, 5 Mar 2008, Cortland Richmond writes: >What are the odds a customer wishing to verify results will use a lab >biased exactly the same as one that gives us a passing result? Not >very good. Articles on Round Robin standard object testing have been >revealing, to say the least. You have to hope that a customer who has enough technical motivation to run a check also has enough technical knowledge to understand the limited repeatability of EMC tests. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk For very important information, please turn over. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: Free Space Antenna Factor
CISPR 16-4 is full of information about measurement uncertainty. For a state of the art configuration the expanded uncertainty is 5.18 dB if I remember well. and that's theory Gert Gremmen Van: emc-p...@ieee.org [mailto:emc-p...@ieee.org] Namens Cortland Richmond Verzonden: woensdag 5 maart 2008 22:08 Aan: emc-p...@ieee.org Onderwerp: Re: Free Space Antenna Factor What are the odds a customer wishing to verify results will use a lab biased exactly the same as one that gives us a passing result? Not very good. Articles on Round Robin standard object testing have been revealing, to say the least. Cortland KA5S >From: Ken Javor >Sent: Mar 5, 2008 10:52 AM >To: Untitled >Subject: Re: Free Space Antenna Factor > >It's quite simple, really. Compliance with FCC/CISPR (now one and the >same?) CE and RE limits means that the probability of causing rfi is low. >Low, but not nonexistent. > >I do not see that shopping around for a test facility that gives the "right >answer" is unscrupulous at all, as long as the test is performed correctly. >However it is highly unlikely. > >In the vast majority of cases, the pressing issue is schedule, not the cost >of the fix itself, so the impetus will be to find a fix, not repeat the test >at different facilities until a favorable site is found. > >Ken Javor > >Phone: (256) 650-5261 > - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: Free Space Antenna Factor
A couple of years ago, at a different company, at the behest of management... I sent a "standard" transmitter around to 5 different labs, including one in Germany. Much to my amusement (I'm always amused when a manager suggests placing bets as an engineering solution) I found that it failed at 5 different frequencies, a different one at each lab. The most suprising thing to me was that the substitution method was used, but the results seemed more typical of a standard site. I second the "Jello with a micrometer" analogy, what we need is the optical comparator solution... Clif From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Cortland Richmond Sent: Wednesday, March 05, 2008 4:08 PM To: emc-p...@ieee.org Subject: Re: Free Space Antenna Factor What are the odds a customer wishing to verify results will use a lab biased exactly the same as one that gives us a passing result? Not very good. Articles on Round Robin standard object testing have been revealing, to say the least. Cortland KA5S >From: Ken Javor >Sent: Mar 5, 2008 10:52 AM >To: Untitled >Subject: Re: Free Space Antenna Factor > >It's quite simple, really. Compliance with FCC/CISPR (now one and the >same?) CE and RE limits means that the probability of causing rfi is low. >Low, but not nonexistent. > >I do not see that shopping around for a test facility that gives the >"right answer" is unscrupulous at all, as long as the test is performed correctly. >However it is highly unlikely. > >In the vast majority of cases, the pressing issue is schedule, not the >cost of the fix itself, so the impetus will be to find a fix, not >repeat the test at different facilities until a favorable site is found. > >Ken Javor > >Phone: (256) 650-5261 > - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Free Space Antenna Factor
What are the odds a customer wishing to verify results will use a lab biased exactly the same as one that gives us a passing result? Not very good. Articles on Round Robin standard object testing have been revealing, to say the least. Cortland KA5S >From: Ken Javor >Sent: Mar 5, 2008 10:52 AM >To: Untitled >Subject: Re: Free Space Antenna Factor > >It's quite simple, really. Compliance with FCC/CISPR (now one and the >same?) CE and RE limits means that the probability of causing rfi is low. >Low, but not nonexistent. > >I do not see that shopping around for a test facility that gives the "right >answer" is unscrupulous at all, as long as the test is performed correctly. >However it is highly unlikely. > >In the vast majority of cases, the pressing issue is schedule, not the cost >of the fix itself, so the impetus will be to find a fix, not repeat the test >at different facilities until a favorable site is found. > >Ken Javor > >Phone: (256) 650-5261 > - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Free Space Antenna Factor
In message , dated Wed, 5 Mar 2008, Ralph McDiarmid writes: >I can see that measurement tolerance from OATs-to-OATs could result in >a pass at one site and a failure at another, for the same test sample. >An unscrupulous company might be tempted to 'shop around' for a pass. It's a costly procedure. Don't imagine for a moment, of course, that test houses talk to each other about peripatetic clients.(;-) > >So, one if left wondering what compliance with the limits really means. Tara!!! It is like measuring Jello with a micrometer. The only saving grace is that what we do at present seems to work, most of the time. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk For very important information, please turn over. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Free Space Antenna Factor
It's quite simple, really. Compliance with FCC/CISPR (now one and the same?) CE and RE limits means that the probability of causing rfi is low. Low, but not nonexistent. I do not see that shopping around for a test facility that gives the "right answer" is unscrupulous at all, as long as the test is performed correctly. However it is highly unlikely. In the vast majority of cases, the pressing issue is schedule, not the cost of the fix itself, so the impetus will be to find a fix, not repeat the test at different facilities until a favorable site is found. Ken Javor Phone: (256) 650-5261 > From: Ralph McDiarmid > Date: Wed, 5 Mar 2008 10:40:45 -0800 > To: > Conversation: Free Space Antenna Factor > Subject: RE: Free Space Antenna Factor > > I can see that measurement tolerance from OATs-to-OATs could result in a pass > at one site and a failure at another, for the same test sample. An > unscrupulous company might be tempted to 'shop around' for a pass. > > So, one if left wondering what compliance with the limits really means. > > > Ralph McDiarmid, AScT > Compliance Engineering Group > Xantrex Technology Inc > > -Original Message- > From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of John Woodgate > Sent: Thursday, February 28, 2008 11:41 PM > To: emc-p...@ieee.org > Subject: Re: Free Space Antenna Factor > > In message , dated Thu, 28 > Feb 2008, Ken Javor writes: > >> If you have two different serial numbers of the same model antenna, and >> the antenna factors one to the next vary as much as shown below, then >> either the antenna quality control is very poor, or (much) more likely >> the antenna calibration tolerances are just that bad (OATS-to-OATS NSA >> can vary 8 dB, right?). > > Agreed. > >> I would have thought that a free space antenna factor would be more >> like 30 meters, especially at 30 MHz, but I?m not an expert on that. > > I would agree. Obviously it depends on how accurate you want to be, but > 10 m seems too close unless the antenna is very small, when it will > anyway have a high antenna factor at 30 MHz. > >> But if the comparison is valid, meaning your colleague?s ten meter >> antenna factor should correlate to your free space factor, then just >> use your colleague?s three meter numbers and be done with it. > > Yes: the uncertainty of your measurements for other reasons is likely to > be quite a lot greater than the difference between the 10 m and 3 m > numbers. > >> You will gain nothing by paying for a three meter calibration of your >> antenna, aside from appeasing some accreditor whose understanding is >> limited to checking calibration stickers and record books. > > Too true. > -- > OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk > For very important information, please turn over. > John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK > > - > > - > > This message is from the IEEE Product Safety Engineering Society > emc-pstc discussion list.Website: http://www.ieee-pses.org/ > > To post a message to the list, send your e-mail to emc-p...@ieee.org > > Instructions: http://listserv.ieee.org/request/user-guide.html > > List rules: http://www.ieee-pses.org/listrules.html > > For help, send mail to the list administrators: > > Scott Douglas emcp...@ptcnh.net > Mike Cantwell mcantw...@ieee.org > > For policy questions, send mail to: > > Jim Bacher: j.bac...@ieee.org > David Heald:emc-p...@daveheald.com > > All emc-pstc postings are archived and searchable on the web at: > > http://www.ieeecommunities.org/emc-pstc - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: Free Space Antenna Factor
I can see that measurement tolerance from OATs-to-OATs could result in a pass at one site and a failure at another, for the same test sample. An unscrupulous company might be tempted to 'shop around' for a pass. So, one if left wondering what compliance with the limits really means. Ralph McDiarmid, AScT Compliance Engineering Group Xantrex Technology Inc From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of John Woodgate Sent: Thursday, February 28, 2008 11:41 PM To: emc-p...@ieee.org Subject: Re: Free Space Antenna Factor In message , dated Thu, 28 Feb 2008, Ken Javor writes: >If you have two different serial numbers of the same model antenna, and >the antenna factors one to the next vary as much as shown below, then >either the antenna quality control is very poor, or (much) more likely >the antenna calibration tolerances are just that bad (OATS-to-OATS NSA >can vary 8 dB, right?). Agreed. > I would have thought that a free space antenna factor would be more >like 30 meters, especially at 30 MHz, but I?m not an expert on that. I would agree. Obviously it depends on how accurate you want to be, but 10 m seems too close unless the antenna is very small, when it will anyway have a high antenna factor at 30 MHz. > But if the comparison is valid, meaning your colleague?s ten meter >antenna factor should correlate to your free space factor, then just >use your colleague?s three meter numbers and be done with it. Yes: the uncertainty of your measurements for other reasons is likely to be quite a lot greater than the difference between the 10 m and 3 m numbers. >You will gain nothing by paying for a three meter calibration of your >antenna, aside from appeasing some accreditor whose understanding is >limited to checking calibration stickers and record books. Too true. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk For very important information, please turn over. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: Free Space Antenna Factor
Thanks for pointing that out. Not too often we get mentioned together :-D What you say is true of course, but my opinion is still that in practical EMI measurements with typical EMI antennas a free-space AF is the best choice whether you measure from 3m or 10m distance. Ari Honkala >-Original Message- >From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf >Of ext Ken Javor >Sent: 29. helmikuuta 2008 10:12 >To: Untitled >Subject: Re: Free Space Antenna Factor > >Mr. Honkala violates the fundamental rule of physics >annunciated by Albert >Einstein: "Everything should be made as simple as possible, but not >simpler." > >While the antenna factor is by definition the ratio of voltage >delivered at >the antenna terminal relative to illuminating electric field, it is the >nature of the illuminating electric field itself which is >different between >three, ten, thirty meters and free space. Free space implies a >plane wave >illumination, the other separations more or less approximate free space >illumination according to frequency and antenna geometry, >because antenna >factor is measured using two identical antennas a fixed >distance apart. The >three, ten or thirty meter antenna factor approaches the free >space factor >when the antenna physical size is small with respect to >separation, making >it look like the point source radiator of a plane wave. > >Ken Javor > >Phone: (256) 650-5261 > > >> From: >> Date: Fri, 29 Feb 2008 09:59:58 +0200 >> To: >> Conversation: Free Space Antenna Factor >> Subject: RE: Free Space Antenna Factor >> >> Back to basics: >> Antenna factor is merely the ratio of E-field strength and >the voltage in >> antenna terminals. >> Therefore it is not related to any distance from source. >> >> It is related to distance from ground plane, but the >free-space AF gives a >> practical average value that is usable when a single figure >is used in >> emission test. >> >> Determination of AF in different ways means different errors in it. >> >> Ari >> >>> -Original Message- >>> From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf >>> Of ext John Woodgate >>> Sent: 29. helmikuuta 2008 9:44 >>> To: emc-p...@ieee.org >>> Subject: Re: Free Space Antenna Factor >>> >>> In message >>> > m>, dated >>> Fri, 29 Feb 2008, ari.honk...@nsn.com writes: >>> >>>> read the appendix 3 of the NPL paper. >>>> They state that " free-space antenna factor is appropriate for 3 m >>>> measurements". >>> >>> What is the context? I think it's a surprising statement if >it is said >>> to be applicable to all possible designs of antenna. >>> -- >>> OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and >www.isce.org.uk >>> For very important information, please turn over. >>> John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK >>> >>> - >>> >>> This message is from the IEEE Product Safety Engineering Society >>> emc-pstc discussion list.Website: http://www.ieee-pses.org/ >>> >>> To post a message to the list, send your e-mail to emc-p...@ieee.org >>> >>> Instructions: http://listserv.ieee.org/request/user-guide.html >>> >>> List rules: http://www.ieee-pses.org/listrules.html >>> >>> For help, send mail to the list administrators: >>> >>> Scott Douglas emcp...@ptcnh.net >>> Mike Cantwell mcantw...@ieee.org >>> >>> For policy questions, send mail to: >>> >>> Jim Bacher: j.bac...@ieee.org >>> David Heald:emc-p...@daveheald.com >>> >>> All emc-pstc postings are archived and searchable on the web at: >>> >>>http://www.ieeecommunities.org/emc-pstc >>> >> >> - >> >> This message is from the IEEE Product Safety Engineering Society >> emc-pstc discussion list.Website: http://www.ieee-pses.org/ >> >> To post a message to the list, send your e-mail to emc-p...@ieee.org >> >> Instructions: http://listserv.ieee.org/request/user-guide.html >> >> List rules: http://www.ieee-pses.org/listrules.html >> >> For help, send mail to the list administrators: >> >> Scott Dougla
Re: Free Space Antenna Factor
In message , dated Fri, 29 Feb 2008, ari.honk...@nsn.com writes: >Antenna factor is merely the ratio of E-field strength and the voltage >in antenna terminals. Therefore it is not related to any distance from >source. But it IS dependent on the characteristics of any objects in the field. At 3 m, an object has more effect than at 10 m, of course. If measured as a receiving antenna, it's not dependent on source distance if the source is very small. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk For very important information, please turn over. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Free Space Antenna Factor
Mr. Honkala violates the fundamental rule of physics annunciated by Albert Einstein: "Everything should be made as simple as possible, but not simpler." While the antenna factor is by definition the ratio of voltage delivered at the antenna terminal relative to illuminating electric field, it is the nature of the illuminating electric field itself which is different between three, ten, thirty meters and free space. Free space implies a plane wave illumination, the other separations more or less approximate free space illumination according to frequency and antenna geometry, because antenna factor is measured using two identical antennas a fixed distance apart. The three, ten or thirty meter antenna factor approaches the free space factor when the antenna physical size is small with respect to separation, making it look like the point source radiator of a plane wave. Ken Javor Phone: (256) 650-5261 > From: > Date: Fri, 29 Feb 2008 09:59:58 +0200 > To: > Conversation: Free Space Antenna Factor > Subject: RE: Free Space Antenna Factor > > Back to basics: > Antenna factor is merely the ratio of E-field strength and the voltage in > antenna terminals. > Therefore it is not related to any distance from source. > > It is related to distance from ground plane, but the free-space AF gives a > practical average value that is usable when a single figure is used in > emission test. > > Determination of AF in different ways means different errors in it. > > Ari > >> -Original Message- >> From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf >> Of ext John Woodgate >> Sent: 29. helmikuuta 2008 9:44 >> To: emc-p...@ieee.org >> Subject: Re: Free Space Antenna Factor >> >> In message >> m>, dated >> Fri, 29 Feb 2008, ari.honk...@nsn.com writes: >> >>> read the appendix 3 of the NPL paper. >>> They state that " free-space antenna factor is appropriate for 3 m >>> measurements". >> >> What is the context? I think it's a surprising statement if it is said >> to be applicable to all possible designs of antenna. >> -- >> OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk >> For very important information, please turn over. >> John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK >> >> - >> >> This message is from the IEEE Product Safety Engineering Society >> emc-pstc discussion list.Website: http://www.ieee-pses.org/ >> >> To post a message to the list, send your e-mail to emc-p...@ieee.org >> >> Instructions: http://listserv.ieee.org/request/user-guide.html >> >> List rules: http://www.ieee-pses.org/listrules.html >> >> For help, send mail to the list administrators: >> >> Scott Douglas emcp...@ptcnh.net >> Mike Cantwell mcantw...@ieee.org >> >> For policy questions, send mail to: >> >> Jim Bacher: j.bac...@ieee.org >> David Heald:emc-p...@daveheald.com >> >> All emc-pstc postings are archived and searchable on the web at: >> >>http://www.ieeecommunities.org/emc-pstc >> > > - > > This message is from the IEEE Product Safety Engineering Society > emc-pstc discussion list.Website: http://www.ieee-pses.org/ > > To post a message to the list, send your e-mail to emc-p...@ieee.org > > Instructions: http://listserv.ieee.org/request/user-guide.html > > List rules: http://www.ieee-pses.org/listrules.html > > For help, send mail to the list administrators: > > Scott Douglas emcp...@ptcnh.net > Mike Cantwell mcantw...@ieee.org > > For policy questions, send mail to: > > Jim Bacher: j.bac...@ieee.org > David Heald:emc-p...@daveheald.com > > All emc-pstc postings are archived and searchable on the web at: > > http://www.ieeecommunities.org/emc-pstc - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: Free Space Antenna Factor
Back to basics: Antenna factor is merely the ratio of E-field strength and the voltage in antenna terminals. Therefore it is not related to any distance from source. It is related to distance from ground plane, but the free-space AF gives a practical average value that is usable when a single figure is used in emission test. Determination of AF in different ways means different errors in it. Ari >-Original Message- >From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf >Of ext John Woodgate >Sent: 29. helmikuuta 2008 9:44 >To: emc-p...@ieee.org >Subject: Re: Free Space Antenna Factor > >In message >, dated >Fri, 29 Feb 2008, ari.honk...@nsn.com writes: > >>read the appendix 3 of the NPL paper. >>They state that " free-space antenna factor is appropriate for 3 m >>measurements". > >What is the context? I think it's a surprising statement if it is said >to be applicable to all possible designs of antenna. >-- >OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk >For very important information, please turn over. >John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK > >- > >This message is from the IEEE Product Safety Engineering Society >emc-pstc discussion list.Website: http://www.ieee-pses.org/ > >To post a message to the list, send your e-mail to emc-p...@ieee.org > >Instructions: http://listserv.ieee.org/request/user-guide.html > >List rules: http://www.ieee-pses.org/listrules.html > >For help, send mail to the list administrators: > > Scott Douglas emcp...@ptcnh.net > Mike Cantwell mcantw...@ieee.org > >For policy questions, send mail to: > > Jim Bacher: j.bac...@ieee.org > David Heald:emc-p...@daveheald.com > >All emc-pstc postings are archived and searchable on the web at: > >http://www.ieeecommunities.org/emc-pstc > - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Free Space Antenna Factor
In message , dated Fri, 29 Feb 2008, ari.honk...@nsn.com writes: >read the appendix 3 of the NPL paper. >They state that " free-space antenna factor is appropriate for 3 m >measurements". What is the context? I think it's a surprising statement if it is said to be applicable to all possible designs of antenna. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk For very important information, please turn over. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Free Space Antenna Factor
In message , dated Thu, 28 Feb 2008, Ken Javor writes: >If you have two different serial numbers of the same model antenna, and >the antenna factors one to the next vary as much as shown below, then >either the antenna quality control is very poor, or (much) more likely >the antenna calibration tolerances are just that bad (OATS-to-OATS NSA >can vary 8 dB, right?). Agreed. > I would have thought that a free space antenna factor would be more >like 30 meters, especially at 30 MHz, but I?m not an expert on that. I would agree. Obviously it depends on how accurate you want to be, but 10 m seems too close unless the antenna is very small, when it will anyway have a high antenna factor at 30 MHz. > But if the comparison is valid, meaning your colleague?s ten meter >antenna factor should correlate to your free space factor, then just >use your colleague?s three meter numbers and be done with it. Yes: the uncertainty of your measurements for other reasons is likely to be quite a lot greater than the difference between the 10 m and 3 m numbers. >You will gain nothing by paying for a three meter calibration of your >antenna, aside from appeasing some accreditor whose understanding is >limited to checking calibration stickers and record books. Too true. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk For very important information, please turn over. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Free Space Antenna Factor
In message <2a93eb060802281828j44085e5dt7db5e969b971...@mail.gmail.com>, dated Thu, 28 Feb 2008, Grace Lin writes: >The antenna vendor told me to use the free space antenna factors, then >compare limit to 10-meter limits. Change vendor! What he is doing is to ignore the 2 dB or so difference in the antenna factors by setting the limit at 3 m 10 dB lower than the standard does. If you do that, your product will, of course, never be caught in violation, but will be up to nearly 10 dB over-tested. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk For very important information, please turn over. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: Free Space Antenna Factor
Grace, read the appendix 3 of the NPL paper. They state that " free-space antenna factor is appropriate for 3 m measurements". This is what we also use as it minimises the uncertainties from height scanning. Note that the free-space AF should not be used if you check your site NSA; there you need height-specific antenna factors. Regards, Ari Honkala _ From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of ext Grace Lin Sent: 29. helmikuuta 2008 4:29 To: Luke Turnbull Cc: emc-p...@ieee.org Subject: Re: Free Space Antenna Factor Dear John, Ken, Luke and others, Thank you so much for your comments. I printed out the document from the link Luke provided. I ran out of time in the office to read it. Please allow me to explain my question more detail. One of antennas I purchased came with free space antenna factors. According to ANSI C63.5: 2006, free space antenna factors are done at 10-meter distance. I will perform radiated emission measurement at 3-meter. Should I use the free space antenna factors without any calculation? Or, is there any equation to convert free space antenna factors for measurement distance other than 10-meter? The antenna vendor told me to use the free space antenna factors, then compare limit to 10-meter limits. I am not convinced to do so as this will have about 10 dB difference. To confirm my concern, I had a friend, who works at a well-known commercial lab and has the same model of the antenna, fax me his antenna factors at 3m and 10m. I list some data below for your reference. Free space antenna factors are from my antenna. 3m and 10m data are horizontal polarization. 30MHz-19.6 (3m), 18.7 (10m), 17.8 (free space) 40MHz-14.2 (3m), 13.7 (10m), 11.9 (free space) 50MHz-9.9 (3m), 9.1 (10m), 7.3 (free space) 60MHz-6.8 (3m), 7.1 (10m), 5.45 (free space) 70MHz-7.2 (3m), 7.3 (10m), 5.2 (free space) 80MHz-8.7 (3m), 7.4 (10m), 6.5 (free space) 90MHz-10.2 (3m), 9.4 (10m), 8.75 (free space) 100MHz-11.8 (3m), 11.3 (10m), 10.5 (free space) 200MHz-10.9 (3m), 10.3 (10m), 9 (free space) 300MHz-14.5 (3m), 13.2 (10m), 13 (free space) 400MHz-17.1 (3m), 16.2 (10m), 15.9 (free space) 500MHz-18.6 (3m), 17.5 (10m), 17.25 (free space) 600MHz-19.9 (3m), 18.6 (10m), 18.5 (free space) 700MHz-20.2 (3m), 18.8 (10m), 19.18 (free space) 800MHz-21.3 (3m), 19.9 (10m), 19.6 (free space) 900MHz-22.2 (3m), 20.8 (10m), 20.35 (free space) 1000MHz-22.9 (3m), 20.9 (10m), 20.9 (free space) >From the above data, I don't find any difference between 3m and 10m close to 10 dB. Thank you and look forward to your help. Best regards, Grace On 2/28/08, Luke Turnbull wrote: Grace, Have a look at the following guide from NPL, Page 41. (Sorry, you have to give them your name and address to download it). The correction is because the actual receiving element of a log-periodic may vary in distance between about 2.5 and 3.5m. The correction gives the field that would be at 3m distance from the product. http://publications.npl.co.uk/npl_web/pdf/mgpg4.pdf Good Luck, Luke Turnbull >>> "Grace Lin" 27 February 2008 18:48 >>> Dear Members, Could someone please teach me how to scale free space antenna factors for my 3-meter distance measurement? One antenna vendor told me that I could scale free space antenna factors. I couldn't reach this vendor at the moment. Thank you and look forward to hearing from you. Best regards, Grace - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Conekt is a trading division of TRW Limited Registered in England, No. 872948 Registered Office Address: Stratford Road, Solihull B90 4AX - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:
Re: Free Space Antenna Factor
The second sentence of the first paragraph below is unclear. I meant to say there was as much difference between your free space antenna factor and the colleague’s ten meter factors as between the three and ten meter factors. Ken Javor Phone: (256) 650-5261 _ From: Ken Javor List-Post: emc-pstc@listserv.ieee.org Date: Thu, 28 Feb 2008 22:06:46 -0600 To: Untitled Conversation: Free Space Antenna Factor Subject: Re: Free Space Antenna Factor I think the antenna factor data confirmed Mr. Woodgate’s assessment of your antenna salesperson. From a practical point-of-view, I would say that since there is as much difference on average between your free space antenna factors and the ten meter antenna factor of your colleague’s antenna, go ahead and use his three meter antenna factors and don’t sweat the details. I am really interested in Mr. Woodgate’s response to the following assertion, upon which the previous statement was based. If you have two different serial numbers of the same model antenna, and the antenna factors one to the next vary as much as shown below, then either the antenna quality control is very poor, or (much) more likely the antenna calibration tolerances are just that bad (OATS-to-OATS NSA can vary 8 dB, right?). I would have thought that a free space antenna factor would be more like 30 meters, especially at 30 MHz, but I’m not an expert on that. But if the comparison is valid, meaning your colleague’s ten meter antenna factor should correlate to your free space factor, then just use your colleague’s three meter numbers and be done with it. You will gain nothing by paying for a three meter calibration of your antenna, aside from appeasing some accreditor whose understanding is limited to checking calibration stickers and record books. Ken Javor Phone: (256) 650-5261 _ From: Grace Lin List-Post: emc-pstc@listserv.ieee.org Date: Thu, 28 Feb 2008 21:28:45 -0500 To: Luke Turnbull Cc: Subject: Re: Free Space Antenna Factor Dear John, Ken, Luke and others, Thank you so much for your comments. I printed out the document from the link Luke provided. I ran out of time in the office to read it. Please allow me to explain my question more detail. One of antennas I purchased came with free space antenna factors. According to ANSI C63.5: 2006, free space antenna factors are done at 10-meter distance. I will perform radiated emission measurement at 3-meter. Should I use the free space antenna factors without any calculation? Or, is there any equation to convert free space antenna factors for measurement distance other than 10-meter? The antenna vendor told me to use the free space antenna factors, then compare limit to 10-meter limits. I am not convinced to do so as this will have about 10 dB difference. To confirm my concern, I had a friend, who works at a well-known commercial lab and has the same model of the antenna, fax me his antenna factors at 3m and 10m. I list some data below for your reference. Free space antenna factors are from my antenna. 3m and 10m data are horizontal polarization. 30MHz-19.6 (3m), 18.7 (10m), 17.8 (free space) 40MHz-14.2 (3m), 13.7 (10m), 11.9 (free space) 50MHz-9.9 (3m), 9.1 (10m), 7.3 (free space) 60MHz-6.8 (3m), 7.1 (10m), 5.45 (free space) 70MHz-7.2 (3m), 7.3 (10m), 5.2 (free space) 80MHz-8.7 (3m), 7.4 (10m), 6.5 (free space) 90MHz-10.2 (3m), 9.4 (10m), 8.75 (free space) 100MHz-11.8 (3m), 11.3 (10m), 10.5 (free space) 200MHz-10.9 (3m), 10.3 (10m), 9 (free space) 300MHz-14.5 (3m), 13.2 (10m), 13 (free space) 400MHz-17.1 (3m), 16.2 (10m), 15.9 (free space) 500MHz-18.6 (3m), 17.5 (10m), 17.25 (free space) 600MHz-19.9 (3m), 18.6 (10m), 18.5 (free space) 700MHz-20.2 (3m), 18.8 (10m), 19.18 (free space) 800MHz-21.3 (3m), 19.9 (10m), 19.6 (free space) 900MHz-22.2 (3m), 20.8 (10m), 20.35 (free space) 1000MHz-22.9 (3m), 20.9 (10m), 20.9 (free space) >From the above data, I don't find any difference between 3m and 10m close to 10 dB. Thank you and look forward to your help. Best regards, Grace On 2/28/08, Luke Turnbull wrote: Grace, Have a look at the following guide from NPL, Page 41. (Sorry, you have to give them your name and address to download it). The correction is because the actual receiving element of a log-periodic may vary in distance between about 2.5 and 3.5m. The correction gives the field that would be at 3m distance from the product. http://publications.npl.co.uk/npl_web/pdf/mgpg4.pdf Good Luck, Luke Turnbull >>> "Grace Lin" 27 February 2008 18:48 >>> Dear Members, Could someone please teach me how to scale free space antenna factors for my 3-meter distance measurement? One antenna vendor told me that I could scale free space antenna factors. I couldn't reach this vendor at the moment. Thank you and look forward to hearing from you. Best regards, Grace - -
Re: Free Space Antenna Factor
I think the antenna factor data confirmed Mr. Woodgate’s assessment of your antenna salesperson. From a practical point-of-view, I would say that since there is as much difference on average between your free space antenna factors and the ten meter antenna factor of your colleague’s antenna, go ahead and use his three meter antenna factors and don’t sweat the details. I am really interested in Mr. Woodgate’s response to the following assertion, upon which the previous statement was based. If you have two different serial numbers of the same model antenna, and the antenna factors one to the next vary as much as shown below, then either the antenna quality control is very poor, or (much) more likely the antenna calibration tolerances are just that bad (OATS-to-OATS NSA can vary 8 dB, right?). I would have thought that a free space antenna factor would be more like 30 meters, especially at 30 MHz, but I’m not an expert on that. But if the comparison is valid, meaning your colleague’s ten meter antenna factor should correlate to your free space factor, then just use your colleague’s three meter numbers and be done with it. You will gain nothing by paying for a three meter calibration of your antenna, aside from appeasing some accreditor whose understanding is limited to checking calibration stickers and record books. Ken Javor Phone: (256) 650-5261 _ From: Grace Lin List-Post: emc-pstc@listserv.ieee.org Date: Thu, 28 Feb 2008 21:28:45 -0500 To: Luke Turnbull Cc: Subject: Re: Free Space Antenna Factor Dear John, Ken, Luke and others, Thank you so much for your comments. I printed out the document from the link Luke provided. I ran out of time in the office to read it. Please allow me to explain my question more detail. One of antennas I purchased came with free space antenna factors. According to ANSI C63.5: 2006, free space antenna factors are done at 10-meter distance. I will perform radiated emission measurement at 3-meter. Should I use the free space antenna factors without any calculation? Or, is there any equation to convert free space antenna factors for measurement distance other than 10-meter? The antenna vendor told me to use the free space antenna factors, then compare limit to 10-meter limits. I am not convinced to do so as this will have about 10 dB difference. To confirm my concern, I had a friend, who works at a well-known commercial lab and has the same model of the antenna, fax me his antenna factors at 3m and 10m. I list some data below for your reference. Free space antenna factors are from my antenna. 3m and 10m data are horizontal polarization. 30MHz-19.6 (3m), 18.7 (10m), 17.8 (free space) 40MHz-14.2 (3m), 13.7 (10m), 11.9 (free space) 50MHz-9.9 (3m), 9.1 (10m), 7.3 (free space) 60MHz-6.8 (3m), 7.1 (10m), 5.45 (free space) 70MHz-7.2 (3m), 7.3 (10m), 5.2 (free space) 80MHz-8.7 (3m), 7.4 (10m), 6.5 (free space) 90MHz-10.2 (3m), 9.4 (10m), 8.75 (free space) 100MHz-11.8 (3m), 11.3 (10m), 10.5 (free space) 200MHz-10.9 (3m), 10.3 (10m), 9 (free space) 300MHz-14.5 (3m), 13.2 (10m), 13 (free space) 400MHz-17.1 (3m), 16.2 (10m), 15.9 (free space) 500MHz-18.6 (3m), 17.5 (10m), 17.25 (free space) 600MHz-19.9 (3m), 18.6 (10m), 18.5 (free space) 700MHz-20.2 (3m), 18.8 (10m), 19.18 (free space) 800MHz-21.3 (3m), 19.9 (10m), 19.6 (free space) 900MHz-22.2 (3m), 20.8 (10m), 20.35 (free space) 1000MHz-22.9 (3m), 20.9 (10m), 20.9 (free space) >From the above data, I don't find any difference between 3m and 10m close to 10 dB. Thank you and look forward to your help. Best regards, Grace On 2/28/08, Luke Turnbull wrote: Grace, Have a look at the following guide from NPL, Page 41. (Sorry, you have to give them your name and address to download it). The correction is because the actual receiving element of a log-periodic may vary in distance between about 2.5 and 3.5m. The correction gives the field that would be at 3m distance from the product. http://publications.npl.co.uk/npl_web/pdf/mgpg4.pdf Good Luck, Luke Turnbull >>> "Grace Lin" 27 February 2008 18:48 >>> Dear Members, Could someone please teach me how to scale free space antenna factors for my 3-meter distance measurement? One antenna vendor told me that I could scale free space antenna factors. I couldn't reach this vendor at the moment. Thank you and look forward to hearing from you. Best regards, Grace - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy que
Re: Free Space Antenna Factor
Dear John, Ken, Luke and others, Thank you so much for your comments. I printed out the document from the link Luke provided. I ran out of time in the office to read it. Please allow me to explain my question more detail. One of antennas I purchased came with free space antenna factors. According to ANSI C63.5: 2006, free space antenna factors are done at 10-meter distance. I will perform radiated emission measurement at 3-meter. Should I use the free space antenna factors without any calculation? Or, is there any equation to convert free space antenna factors for measurement distance other than 10-meter? The antenna vendor told me to use the free space antenna factors, then compare limit to 10-meter limits. I am not convinced to do so as this will have about 10 dB difference. To confirm my concern, I had a friend, who works at a well-known commercial lab and has the same model of the antenna, fax me his antenna factors at 3m and 10m. I list some data below for your reference. Free space antenna factors are from my antenna. 3m and 10m data are horizontal polarization. 30MHz-19.6 (3m), 18.7 (10m), 17.8 (free space) 40MHz-14.2 (3m), 13.7 (10m), 11.9 (free space) 50MHz-9.9 (3m), 9.1 (10m), 7.3 (free space) 60MHz-6.8 (3m), 7.1 (10m), 5.45 (free space) 70MHz-7.2 (3m), 7.3 (10m), 5.2 (free space) 80MHz-8.7 (3m), 7.4 (10m), 6.5 (free space) 90MHz-10.2 (3m), 9.4 (10m), 8.75 (free space) 100MHz-11.8 (3m), 11.3 (10m), 10.5 (free space) 200MHz-10.9 (3m), 10.3 (10m), 9 (free space) 300MHz-14.5 (3m), 13.2 (10m), 13 (free space) 400MHz-17.1 (3m), 16.2 (10m), 15.9 (free space) 500MHz-18.6 (3m), 17.5 (10m), 17.25 (free space) 600MHz-19.9 (3m), 18.6 (10m), 18.5 (free space) 700MHz-20.2 (3m), 18.8 (10m), 19.18 (free space) 800MHz-21.3 (3m), 19.9 (10m), 19.6 (free space) 900MHz-22.2 (3m), 20.8 (10m), 20.35 (free space) 1000MHz-22.9 (3m), 20.9 (10m), 20.9 (free space) >From the above data, I don't find any difference between 3m and 10m close to 10 dB. Thank you and look forward to your help. Best regards, Grace On 2/28/08, Luke Turnbull wrote: Grace, Have a look at the following guide from NPL, Page 41. (Sorry, you have to give them your name and address to download it). The correction is because the actual receiving element of a log-periodic may vary in distance between about 2.5 and 3.5m. The correction gives the field that would be at 3m distance from the product. http://publications.npl.co.uk/npl_web/pdf/mgpg4.pdf Good Luck, Luke Turnbull >>> "Grace Lin" 27 February 2008 18:48 >>> Dear Members, Could someone please teach me how to scale free space antenna factors for my 3-meter distance measurement? One antenna vendor told me that I could scale free space antenna factors. I couldn't reach this vendor at the moment. Thank you and look forward to hearing from you. Best regards, Grace - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Conekt is a trading division of TRW Limited Registered in England, No. 872948 Registered Office Address: Stratford Road, Solihull B90 4AX - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Free Space Antenna Factor
Grace, Have a look at the following guide from NPL, Page 41. (Sorry, you have to give them your name and address to download it). The correction is because the actual receiving element of a log-periodic may vary in distance between about 2.5 and 3.5m. The correction gives the field that would be at 3m distance from the product. http://publications.npl.co.uk/npl_web/pdf/mgpg4.pdf Good Luck, Luke Turnbull >>> "Grace Lin" 27 February 2008 18:48 >>> Dear Members, Could someone please teach me how to scale free space antenna factors for my 3-meter distance measurement? One antenna vendor told me that I could scale free space antenna factors. I couldn't reach this vendor at the moment. Thank you and look forward to hearing from you. Best regards, Grace - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Conekt is a trading division of TRW Limited Registered in England, No. 872948 Registered Office Address: Stratford Road, Solihull B90 4AX - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Free Space Antenna Factor
In message , dated Wed, 27 Feb 2008, Ken Javor writes: >Actually it's Missouri that's the "show me" state, but the point is >well taken. Oops! -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk For very important information, please turn over. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Free Space Antenna Factor
Actually it's Missouri that's the "show me" state, but the point is well taken. A low gain log-periodic or biconical above 200 MHz might approach a free space antenna factor, but I agree that Grace should look at the numbers. The ETS/Lindgren website is a great place to see three and ten meter antenna factors plotted on the same graph: http://www.ets-lindgren.com/page/?i=EMCAntennas Ken Javor Phone: (256) 650-5261 > From: John Woodgate > Date: Wed, 27 Feb 2008 20:55:29 +0000 > To: > Subject: Re: Free Space Antenna Factor > > In message , dated Wed, 27 > Feb 2008, Ken Javor writes: > >> I don?t know what you mean by scaling free space antenna factors. What >> is true is that if the antenna factor used at three meters is no >> different than for free space, then you could theoretically scale the >> three meter measurement to any other separation distance and predict >> what you would measure there, i.e., at ten or thirty meters. > > Isn't that what Grace probably means? The point, however, is 'if'. IF > the antenna factor at 3 m is the same as for free space... But surely it > almost certainly isn't, unless it's a very small antenna? > > What the wicked salesman (;-) is saying is that the AF at, say, 10 m can > also be used at 3 m. Well, maybe. Grace should claim to be from > Minnesota, in my humble opinion! > -- > OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk > For very important information, please turn over. > John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK > > - > > This message is from the IEEE Product Safety Engineering Society > emc-pstc discussion list.Website: http://www.ieee-pses.org/ > > To post a message to the list, send your e-mail to emc-p...@ieee.org > > Instructions: http://listserv.ieee.org/request/user-guide.html > > List rules: http://www.ieee-pses.org/listrules.html > > For help, send mail to the list administrators: > > Scott Douglas emcp...@ptcnh.net > Mike Cantwell mcantw...@ieee.org > > For policy questions, send mail to: > > Jim Bacher: j.bac...@ieee.org > David Heald:emc-p...@daveheald.com > > All emc-pstc postings are archived and searchable on the web at: > > http://www.ieeecommunities.org/emc-pstc - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Free Space Antenna Factor
In message , dated Wed, 27 Feb 2008, Ken Javor writes: >I don?t know what you mean by scaling free space antenna factors. What >is true is that if the antenna factor used at three meters is no >different than for free space, then you could theoretically scale the >three meter measurement to any other separation distance and predict >what you would measure there, i.e., at ten or thirty meters. Isn't that what Grace probably means? The point, however, is 'if'. IF the antenna factor at 3 m is the same as for free space... But surely it almost certainly isn't, unless it's a very small antenna? What the wicked salesman (;-) is saying is that the AF at, say, 10 m can also be used at 3 m. Well, maybe. Grace should claim to be from Minnesota, in my humble opinion! -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk For very important information, please turn over. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Free Space Antenna Factor
I don’t know what you mean by scaling free space antenna factors. What is true is that if the antenna factor used at three meters is no different than for free space, then you could theoretically scale the three meter measurement to any other separation distance and predict what you would measure there, i.e., at ten or thirty meters. Ken Javor Phone: (256) 650-5261 _ From: Grace Lin List-Post: emc-pstc@listserv.ieee.org Date: Wed, 27 Feb 2008 13:48:53 -0500 To: Subject: Free Space Antenna Factor Dear Members, Could someone please teach me how to scale free space antenna factors for my 3-meter distance measurement? One antenna vendor told me that I could scale free space antenna factors. I couldn't reach this vendor at the moment. Thank you and look forward to hearing from you. Best regards, Grace - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Free Space Antenna Factor
Dear Members, Could someone please teach me how to scale free space antenna factors for my 3-meter distance measurement? One antenna vendor told me that I could scale free space antenna factors. I couldn't reach this vendor at the moment. Thank you and look forward to hearing from you. Best regards, Grace - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
