Answer: The
procedures for measuring radiated emissions for intentional and unintentional
radiator devices are found in ANSI C63.10-2013 and ANSI C63.4-2014,
respectively, including recommended types of measurement antennas. It is not acceptable to use an active or
passive monopole (rod) antenna when performing measurements to demonstrate
compliance with the FCC radiated emission limits below 30 MHz. Calibrated loop antennas generally provide
more accurate and repeatable field strength measurement results below 30 MHz
[FCC 03-149, Second Report and Order, docket no. 01-278, para. 40]. Per Section
15.31, the monopole antenna provisions in 4.5.3 and 8.2.2 of ANSI C63.4-2014 are
excluded for FCC compliance testing purposes.
Unintentional
Radiators: Subclause 4.5 of ANSI C63.4-2014 provides information on selecting
the correct measurement antenna for radiated emission measurements. Footnote b to Table 2 of ANSI C63.4 explains
the restriction on the use of the monopole (rod) antennas for compliance
measurements below 30 MHz.
Intentional
Radiators: Subclause 4.3.1 of ANSI C63.10-2013 provides information on
selecting the correct measurement antenna for radiated emission measurements. Footnote b to Table 1 of ANSI C63.10 explains
the restriction on the use of monopole (rod) antennas for compliance
measurements below 30 MHz.
When performing radiated emission measurements below 30 MHz for
compliance testing of Part 15 and Part 18 devices, use of either an active or
passive loop antenna is required. Other
information about test sites and antennas for radiated emission measurements
below 30 MHz is given in KDB Publications 414788 and 629601.
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