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FCC Part 15 Radio Frequency Devices
Section 15.35

The Federal Communications Commission (FCC) is the authority in the United States of America that creates and enforces the use of airwaves throughout the entire radio frequency spectrum. This group of documents contains the entirety of the FCC Part 15 regulations that concern unlicensed radio frequency devices. As with all government documents, this material is in the public domain and may be freely copied so long as the content is not changed. This copy is provided as a convenience for RF Cafe visitors. 

Click here for the Table of Contents.

[Code of Federal Regulations]
[Title 47, Volume 1]
[Revised as of October 1, 2008]
From the U.S. Government Printing Office via GPO Access
[CITE: 47CFR15.35]
[Page 762]
                       TITLE 47--TELECOMMUNICATION
                            Subpart A_General
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 
    (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 
    (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]

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