§  15.35   Measurement detector functions and bandwidths.

   The conducted and radiated emission limits shown in this part are based
   on the following, unless otherwise specified elsewhere in this part:

   (a) On any frequency or frequencies below or equal to 1000 MHz, the
   limits shown are based on measuring equipment employing a CISPR
   quasi-peak detector function and related measurement bandwidths, unless
   otherwise specified. The specifications for the measuring instrument
   using the CISPR quasi-peak detector can be found in Publication 16 of
   the International Special Committee on Radio Interference (CISPR) of
   the International Electrotechnical Commission. As an alternative to
   CISPR quasi-peak measurements, the responsible party, at its option,
   may demonstrate compliance with the emission limits using measuring
   equipment employing a peak detector function, properly adjusted for
   such factors as pulse desensitization, as long as the same bandwidths
   as indicated for CISPR quasi-peak measurements are employed.

   Note: For pulse modulated devices with a pulse-repetition frequency of
   20 Hz or less and for which CISPR quasi-peak measurements are
   specified, compliance with the regulations shall be demonstrated using
   measuring equipment employing a peak detector function, properly
   adjusted for such factors as pulse desensitization, using the same
   measurement bandwidths that are indicated for CISPR quasi-peak
   measurements.

   (b) Unless otherwise specified, on any frequency or frequencies above
   1000 MHz, the radiated emission limits are based on the use of
   measurement instrumentation employing an average detector function.
   Unless otherwise specified, measurements above 1000 MHz shall be
   performed using a minimum resolution bandwidth of 1 MHz. When average
   radiated emission measurements are specified in this part, including
   average emission measurements below 1000 MHz, there also is a limit on
   the peak level of the radio frequency emissions. Unless otherwise
   specified, e.g. , see § § 15.250, 15.252, 15.255, and 15.509-15.519,
   the limit on peak radio frequency emissions is 20 dB above the maximum
   permitted average emission limit applicable to the equipment under
   test. This peak limit applies to the total peak emission level radiated
   by the device, e.g. , the total peak power level. Note that the use of
   a pulse desensitization correction factor may be needed to determine
   the total peak emission level. The instruction manual or application
   note for the measurement instrument should be consulted for determining
   pulse desensitization factors, as necessary.

   (c) Unless otherwise specified, e.g. § 15.255(b), when the radiated
   emission limits are expressed in terms of the average value of the
   emission, and pulsed operation is employed, the measurement field
   strength shall be determined by averaging over one complete pulse
   train, including blanking intervals, as long as the pulse train does
   not exceed 0.1 seconds. As an alternative (provided the transmitter
   operates for longer than 0.1 seconds) or in cases where the pulse train
   exceeds 0.1 seconds, the measured field strength shall be determined
   from the average absolute voltage during a 0.1 second interval during
   which the field strength is at its maximum value. The exact method of
   calculating the average field strength shall be submitted with any
   application for certification or shall be retained in the measurement
   data file for equipment subject to notification or verification.

   [ 54 FR 17714 , Apr. 25, 1989, as amended at  56 FR 13083 , Mar. 29, 1991;
    61 FR 14502 , Apr. 2, 1996;  63 FR 42279 , Aug. 7, 1998;  67 FR 34855 , May
   16, 2002;  70 FR 6773 , Feb. 9, 2005]