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) On any frequency or frequencies above 1000 MHz, unless otherwise 
stated, the radiated limits shown are based on the use of measurement 
instrumentation employing an average detector function. When average 
radiated emission measurements are specified in the regulations, 
including emission measurements below 1000 MHz, there is also a limit on 
the radio frequency emissions, as measured using instrumentation with a 
peak detector function, corresponding to 20 dB above the maximum 
permitted average limit for the frequency being investigated. Unless 
otherwise specified, measurements above 1000 MHz shall be performed 
using a minimum resolution bandwidth of 1 MHz. Measurements of AC power 
line conducted emissions are performed using a CISPR quasi-peak 
detector, even for devices for which average radiated emission 
measurements are specified.
    (c) When the radiated emission limits are expressed in terms of the 
average value of the emission, and pulsed operation is employed, the 
measured 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 those 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]