"The original intent of ANSI C63.5-1988 was to compare the normalized site attenuation of a semianechoic chamber to a theoretical NSA calculated using free-space antenna factors," says Robert F. German, manager of German Training and Consulting LLC (Boulder, CO). German explains that the accepted interpretation of the standard, however, allows a direct site-to-site NSA comparison between a chamber and an unspecified OATS.

Don Heirman, president of Don Heirman Consultants and chairman of the working group and subcommittee, rejects the idea that this is an issue. "Differing opinions are openly discussed and are being addressed as part of the working group's due process and deliberations," he says.

German says that as industry gained experience with the standard, some found it difficult to design and build a semianechoic chamber with NSA within ±4 dB of the theoretical model. "They soon found a way around the requirement using the site-to-site comparisons," he says. "Unfortunately, the FCC has accepted this interpretation, and now there is no effective control of chamber performance."

Don Heirman

In an effort to create correction factors for ideal site attenuation when measured with biconical and log-periodic antennas, the ANSI ASC C63, Subcommittee 1, working group met November 4. It presented its results on the two affected standards: site validation (ANSI C63.4) and antenna calibration (ANSI C63.5). The subcommittee must determine whether to forward these changes to the parent C63 committee for balloting.

Because the 1998 version is said to be more difficult to meet, it is anticipated that the revision to C63.4 will allow either version to be used when validating a semianechoic chamber. "In the meantime, we have accommodated the industry needs by their having the ability to order both standards until the committee has concluded its deliberations," says Heirman.

Heirman points out that "the 1988 version of the standard has been used internationally as well as nationally for the past 11 years for calibrating antennas to use in qualifying test sites." After receiving feedback on the first revision, the subcommittee is expected to recommend that C63.4 reference both the 1988 and 1998 versions. "In the meantime," German says, "many people want the revision of C63.4 to only reference C63.5-1988 because C63.5-1998 does not allow site-to-site comparisons. If you reference the 1988 version, you effectively have no standard. If you reference the 1998 version, you have a standard that only a few can meet. If you reference both, you still have a standard with a loophole," says German. The only solution to this situation, he says, is for C63.4 to reference both versions of C63.5 and to rigorously verify the performance of the near-ideal OATS used for a direct site-to-site NSA comparison.

But, the committee's measured approach is necessary, Heirman says. "We are cautious about putting the test industry and test facility industry, as well as their customer base, in jeopardy," he says. "We are trying to be fair and open in our committee."

Any changes beyond the 1998 version, Heirman says, must be carefully crafted so that they do not affect sites presently qualified using the 1988 version. "It is the goal that the modifications of both standards taken as a package will not significantly affect presently qualified test sites, unless the standards' modifications show site anomalies that deserve such corrections."

At the working group meeting in November, the committee addressed its progress on a validation model for site attenuation, validation of test sites, and calibration of antennas. "These revisions augment the use of tuned dipole antennas, which is required in some regions of the world, to the use of biconical antennas (30–200 MHz) and log periodic arrays (200–1000 MHz)," says Heirman.

Heirman says that the proposed amendment offers emission test chamber manufacturers or purchasers additional options for specifying the "tightness" of acceptable deviation of site attenuation from theoretical models.

The suggested changes, he says, are the result of a lack of international harmonization and poor correlation between test sites. "Different countries have different models that provide different site-attenuation and antenna-factor results. This leads to chamber construction and absorber use that differ, perhaps unnecessarily," Heirman says. "In addition, some countries only allow certain antenna types, such as tuned resonant dipoles, to be used in performing site attenuation, where in fact broadband antennas can be used with equal acceptability (using the new model being developed in the working group). This has at times led to redundant measurement of site validation."

FCC has not yet adopted the 1998 version since the reference is contained in C63.4, which itself is under ballot for the 1999 version, Heirman says. The enhanced theoretical model for site attenuation and antenna calibration is considered to be more accurate, he says. It will be proposed for the next edition of ANSI C63.4, which will likely be up for discussion within the next two years.

For 40 years, Jonassen was an educator, teaching classes on physics at the Technical University. He also taught 70 extended courses on static electricity, ions, and indoor climate. In 1989, he
received the ESD Association's Outstanding Contribution Award.

He twice served as a United Nations specialist for the International Atomic Energy Agency, advising the agency on radon projects in the Philippines. Jonassen served on the board of directors for the Technical University of Denmark and was head of the Laboratory of Applied Physics.

Jonassen received his MS degree from the University of Copenhagen in 1954 and his DSc from the Technical University of Denmark in 1962. The same year, he won the Danish Esso Prize for his work on industrial static electricity.

When he is not busy running his laboratory, Jonassen can be found indulging his love of country music and studying Thai cooking—in Thailand. In his own words, "There's more to life than static electricity."

If highway speed limits were increased from 55 to 550 mph, the results would be disastrous. But that's what has happened—so to speak—to system speeds during the past 20 years, notes new board member William Kimmel, PE. Add the increased system speeds to the proliferating electronics market, and, "It's no wonder we have problems," Kimmel says. "No modern electronic system is immune from EMI effects."

Prior to forming KGA, Kimmel worked on electronic design, systems engineering, and technical management assignments for Sperry Corp. and Control Data Corp. His EMC experience includes design, test, and qualification of military systems to MIL-STD-461 and TEMPEST requirements, industrial and commercial systems to FCC and CISPR/IEC, and medical devices to FDA requirements. He has solved EMI problems in computers, medical devices, industrial controls, vehicles, and telecommunications.

Kimmel received his BSEE with distinction from the University of Minnesota, and he is a registered professional engineer (PE) and a NARTE-certified EMC and ESD engineer.