Sec.  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  Sec.  Sec. 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.  Sec. 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]