I was going to stay out of this, but I feel I must jump in. Harry's position is not the unanimous position of the members of C63 SC 1. 3 different members presented data at the October meeting that indicate that the difference in results between hybrid antennas and bicon/log periodic antennas is minimal. While it is true that some hybrid antennas are not suitable for radiated emissions measurements, it should be pointed out that typically these antennas are built for radiated immunity testing and are so marketed by their manufacturers. In addition, the current draft of C63.4-2012 out for vote within the subcommittee does in fact now have an entry for hybrid antennas, and it does not prohibit their use for qualification measurements on products. This is not a settled issue, so stay tuned.
Ghery S. Pettit From: [email protected] [mailto:[email protected]] On Behalf Of Martin E. Cormier Sent: Monday, January 16, 2012 6:15 AM To: [email protected] Subject: Re: Fwd: [PSES] Biconilog antennas and ANSI C63.4:2009 Dear Mr Hodes, First of all, thank you for taking the time to answer my question so eloquently. I will keep your post on file to go back to if I ever need to discuss any aspect of it with an eventual assessor. Also, yes, using the term "bilog" to describe an LPDA was my mistake and I realized it after my post. I never meant to imply that Table 1 allowed what I will now call a hybrid antenna to perform measurements. Not having done all the math and research, I can only rely on gut feeling to think that using the same antenna that was used to measure NSA must mean something about the validity of the measurements it takes of a test setup. But it is also why I will not try to defend this point beyond mention. I am still trying to digest the "40dB difference" mentioned by Mr Violette. The purpose of my post was to, of course, try to prevent an eventual deficiency, but also to make sure we are using the best method to maintain confidence in the measurements we take. No, we will not go back to using tuned dipoles to measure emissions, but we will find a method in-between. It's just frustrating that it will probably mean additional expenses and elongated certification time, while affecting our uncertainty figure due to the manipulation needed to change antennas many times a day. I will not look at lab promotional documents showing a nice hybrid antenna in a new chamber the same way from now on. Martin On 2012-01-13 5:01 PM, Harry Hodes wrote: Dear Mr. Cormier, Mike Violette of Washington Labs took the liberty of forwarding to me your recent EMC-PSTC LISTSERV posting on the topic of the use of biconlog antenna in ANSI C63.4-2009. (I do not normally follow the EMC-PSTC LISTSERV). In order for you to judge the validity of my answer to the question that you raised in your recent LISTSERV posting, I first will tell you a bit about the Accredited Standards Committee C63(r) and then about myself and my relationship to the Accredited Standards Committee C63(r). The Accredited Standards Committee C63(r) is a major United States-based EMC standards developers focused on many aspects of emission and immunity measurements, instrumentation, and resources for test lab competency and quality control. Its standards development activities are highly diversified. One of the most important aspects of the Accredited Standards Committee C63(r) is the acceptance of its standards by US regulatory agencies including the Federal Communications Commission (FCC). The FCC explicitly references several Accredited Standards Committee C63(r) standards (including the EMC Emissions Testing Standard ANSI C63.4 and EMC Antenna Calibration Standard ANSI C63.5) in its Rules (i.e., in 47 CFR). I have worked as an EMC Engineer for 33 years, and for the last 15 of those years I have either co-owned or individually owned Independent Third party EMC Test Labs that were ISO/IEC 17025-accredited for a Scope of Accreditation that included ANSI C63.4. I am the American Council of Independent Laboratories [ACIL] Conformity Assessment Section [CAS] Vice-chairman, and I am the Chief of the Editorial Board of the ACIL's EMC Standards Alert Newsletter. Also, I am the ACIL CAS's Alternate Voting Member of the Accredited Standards Committee C63(r). For the last few years, I have been a member of the Subcommitte 1 (SC1) Working Groups that are actually responsible for the detailed technical writing and maintenance tasks for the ANSI C63.4 and ANSI C63.5 Standards. I was active in the many-months-long SC1 review process that ultimately resulted in the publication of ANSI C63.4-2009. I am a current and very active member of the SC1 Working Group Maintenance Teams that are preparing the texts of the upcoming versions of both ANSI C63.4 and ANSI C63.5 - both of which will be published this year. In other words, I was there and awake each time the issue raised in your LISTSERV posting has come up over the last 3 years! Now, for my reply to your question: First, Table 1 of ANSI C63.4-2009 is Normative. That means that its application is mandatory as writen - it is NOT a list of suggestions. In other words, the ONLY antennas that are allowed to be used for making (final compliance) Radiated Emissions Measurements per ANSI C63.4-2009 are those antenna types explicitly listed in Table 1. Additionally, the antenna types listed in Table 1 are ONLY to be used over the frequency range(s) given for those antenna types in Table 1. In the frequency range 30 MHz to 1000 MHz, Table 1 of ANSI C63.4-2009 specifically lists: - Dipole (passive) antennas (which are required to be tuned - i.e., are narrowband antennas). [Note: per ANSI C63.5, only Roberts-type tuned dipoles are allowed to be used]. - Biconical Dipole antennas (which are center-fed dipole "fat" antennas having multi-octave broadband performance). Such antenna have either a 50 Ohm balun or a 200 Ohm balun and are fitted with two "birdcage" elements). - Log Periodic Dipole Array antennas (which have doubly-stacked dipole elements spaced logarithmically apart, so that the antenna is multi-octave broadband). [Note that Log Periodic Dipole Array Antennas are NOT Yagi Antennas - a Yagi antenna has linearly-spaced elements that yield quite high power gain and very narrow directivity and have bandwidths on the order of 10% to 20% of an octave of frequency. In contrast, Log Periodic Dipole Array Antennas are multi-octive broadbanded antennas with better directivity than a tuned dipole and only slightly higher gain than a tuned dipole]. - Double-ridged Guide Horn antennas (which are exactly what their name says they are). Second, despite what you stated in your LISTSERV posting, Table 1 of ANSI C63.4-2009 does NOT in any way mention or list "bilogs". EMC Antenna terminology is often confusing, so let me say that the term "bilog" is actually a trade name for one specific brand of hybrid antenna. (The term "hybrid" should always be used unless one is referering to a specific Make and Model of antenna whose trade-name is "Bilog"). Third, I must state that it was NEVER the intent of the writers of ANSI C63.4-2009 to allow the use of hybrid antennas for making (final compliance) Radiated Emissions Measurements per ANSI C63.4-2009. Additionally, (although you did not raise this point) it was NEVER the intent of the writers of ANSI C63.4-2009 to allow the use of hybrid antennas for making Site Validation Measurements (i.e., standard or volumetric Normalized Site Attenuation measurements) per ANSI C63.4-2009. The intention of the writers of ANSI C63.4-2009 to prohibit the use of hybrid antennas for making final compliance measurements is clearly stated in the NORMATIVE interpretation that can be found (along with all of the other NORMATIVE interpretions issued for ANSI C63 Standards) at the following URL: http://www.c63.org/documents/misc/posting/new_interpretations.htm Please note that the interpretation to which I am referring is entitled "Use of hybrid antenna above 1 GHz". That said, if your read that interpretation, the same logic applies regarding the use of hybrid antennas from 30 MHz to 1 GHz. Fourth, the ASC 63 have a series of annual meetings with the lab assessors of each of the US EMC Lab accrediting bodies. At these sessions, the ASC 63 representative (typically Don Heirman, who just ended his term as Chair of ASC 63), has made a considerable effort to educate the assessors that the must cite a deficiency against any EMC Lab that uses hybrid antennas for making final compliance measurements (and/or site validation measurements) per ANSI C63.4-2009. All that said, you might well ask why every EMC Test Lab that uses hybrid antennas (for making (final compliance) Radiated Emissions Measurements and/or Site Validation Measurements per ANSI C63.4-2009) has not been given a "hard time" during an Accreditation audit? The answer to that question is complex. However, if we confine ourseves strictly to what is stated explictly in the standard, we can see the following problem: In ANSI C63.4-2009 it is stated in clause 4.5: Table 1 provides a summary listing of antennas and typical frequency ranges. This wording clearly indicates that the antenna type for a specific frequency range is really mandatory since the table states "yes" or "no", indicating that the antenna type is (or is not) to be used in the identified frequency range. However, in ANSI C63.4-2009 clause 4.5.3 the following is stated: Linearly polarized antennas as specified in ANSI C63.2 shall be used to measure electric fields in the frequency range of 30 MHz to 1000 MHz (see also CISPR 16-1-4:2007). Since ANSI C63.2 is referenced without a date in clause 2 of ANSI C63.4-2009, the latest revision of ANSI C63.2 is to be looked at - i.e., ANSI C63.2-2009. Now, in CISPR 16-1-4:2007 clause 4.5.1 it is stated that: The antenna shall be a dipole-like antenna designed to measure the E-field, and the free-space antenna factor shall be used. The antenna types include: a) tuned dipole antennas, whose element pairs are either straight rods or conical in shape; b) dipole arrays such as the log-periodic dipole array (LPDA) antennas, comprising a series of staggered sets of straight rod elements; c) and hybrid antennas. [emphasis added]. As a result of the above, some (but by no means all) auditors take the position that due to the reference to ANSI C63.2, the exclusion of hybrid antennas cannot necessarily be assumed - notwithstanding the clear direction stated in the interpretation mentioned above. This is because there is at least the appearance of a conflict in the applicable standards. Specifically, ANSI C63.4-2009 Table 1 calls out a specific antenna type for the identified frequency range, but, clause 4.5.3 of ANSI C63.4-2009 refers to ANSI C63.2 which in turn refers to CISPR 16-1-4:2007, which specifically ALLOWS the use of hybrid antennas. This reference cannot just be "argued away" because the (undated) ANSI C63.2 reference is stated explicitly in the normative text of ANSI C63.4-2009 clause 4.5.3, and, is a normative reference in clause 2 of ANSI C63.4-2009. For this reason, some auditors are very reluctant to disallow the use of hybrid antennas from 30 MHz to 1000 MHz for the making of final compliance measurements. I am sorry that this answer is so long and so complex. This is a topic that has generated a great deal of controvery over the last three years. Looking to the future, it is possible (but is by no means certain) that the use of some types of hybrid antennas may be allowed in in the next edition of ANSI C63.4. If this does happen, the use of such hybrid antennas will be subject to a series of strict dimensional and technical performance criteria (which will likely include in-house qualification testing) that will be stated in the next edition of ANSI C63.5. As for what you should do in your EMC Test Lab, it is not my place to say. If I were your accreditation auditor, I certainly would cite a deficiency if you used a hybrid antenna for making final compliance radiated emissions measurements per ANSI C63.4-2009. Yours sincerely, Harry. H. Hodes Principal EMC Engineer President & CEO Acme Testing Co. From: Mike Violette <[email protected]><mailto:[email protected]> To: "[email protected] Hodes"<mailto:[email protected]> <[email protected]><mailto:[email protected]> Sent: Friday, January 13, 2012 5:54 AM Subject: Fwd: [PSES] Biconilog antennas and ANSI C63.4:2009 Hi Harry, Care to comment back to M. Cormier? Mike Mike Violette Washington Laboratories & American Certification Body [email protected]<mailto:[email protected]> +1 240 401 1388 Begin forwarded message: From: "Martin E. Cormier" <[email protected]<mailto:[email protected]>> Date: January 13, 2012 8:13:53 AM EST To: "[email protected]<mailto:[email protected]>" <[email protected]<mailto:[email protected]>> Subject: [PSES] Biconilog antennas and ANSI C63.4:2009 Reply-To: "Martin E. Cormier" <[email protected]<mailto:[email protected]>> Hello everyone, I am relatively new to this mailing list, so this question may have been posted before. I did not find it when searching the archive. It has come to my attention yesterday that some accreditors may give a lab a hard time if it tries to get ANSI C63.4:2009 accreditation when using biconilog broadband antennas for measurements from 30MHz to 1GHz. Table 1 does not explicitely list combination antennas as allowed, but both biconicals and bilogs are listed as OK for this frequency range. Has anyone here been subjected to accreditation issues for using biconilogs? Thanks, Martin (Sorry if my English is bad, second language for me) - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]<mailto:[email protected]>> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.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 <[email protected]><mailto:[email protected]> Mike Cantwell <[email protected]><mailto:[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]><mailto:[email protected]> David Heald: <[email protected]><mailto:[email protected]> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]<mailto:[email protected]>> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.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 <[email protected]<mailto:[email protected]>> Mike Cantwell <[email protected]<mailto:[email protected]>> For policy questions, send mail to: Jim Bacher <[email protected]<mailto:[email protected]>> David Heald <[email protected]<mailto:[email protected]>> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
