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FCC Part 15 Radio Frequency Devices
Section 15.31

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: 47CFR15.31]
[Page 756-760]
 
                       TITLE 47--TELECOMMUNICATION
 
              CHAPTER I--FEDERAL COMMUNICATIONS COMMISSION
 
PART 15_RADIO FREQUENCY DEVICES--Table of Contents
 
                            Subpart A_General
 
Sec. 15.31  Measurement standards.
    (a) The following measurement procedures are used by the Commission 
to determine compliance with the technical requirements in this part. 
Except where noted, copies of these procedures are available from the 
Commission's current duplicating contractor whose name and address are 
available from the Commission's Consumer and Governmental Affairs Bureau 
at 1-888-CALL-FCC (1-888-225-5322).
    (1) FCC/OET MP-2: Measurement of UHF Noise Figures of TV Receivers.
    (2) Unlicensed Personal Communication Service (UPCS) devices are to 
be measured for compliance using ANSI C63.17-1998: ``Methods of 
Measurement of the Electromagnetic and Operational Compatibility of 
Unlicensed Personal Communications Services (UPCS) Devices'', 
(incorporated by reference, see Sec. 15.38). This incorporation by 
reference was approved by the Director of the Federal Register in 
accordance with 5 U.S.C. 552(a) and 1 CFR part 51.
    (3) Other intentional and unintentional radiators are to be measured 
for compliance using the following procedure excluding sections 4.1.5.2, 
5.7, 9 and 14: ANSI C63.4-2003: ``Methods of Measurement of Radio-Noise 
Emissions from Low-Voltage Electrical and Electronic Equipment in the 
Range of 9 kHz to 40 GHz'' (incorporated by reference, see Sec. 15.38). 
This incorporation by reference was approved by the Director of the 
Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51.
    Note to paragraph (a)(3): Digital devices tested to show compliance 
with the provisions of Sec. Sec. 15.107(e) and 15.109(g) must be tested 
following the ANSI C63.4 procedure described in paragraph (a)(3) of this 
section.
    (b) All parties making compliance measurements on equipment subject 
to the requirements of this part are urged to use these measurement 
procedures.
[[Page 757]]
Any party using other procedures should ensure that such other 
procedures can be relied on to produce measurement results compatible 
with the FCC measurement procedures. The description of the measurement 
procedure used in testing the equipment for compliance and a list of the 
test equipment actually employed shall be made part of an application 
for certification or included with the data required to be retained by 
the party responsible for devices authorized pursuant to a Declaration 
of Conformity or devices subject to verification.
    (c) For swept frequency equipment, measurements shall be made with 
the frequency sweep stopped at those frequencies chosen for the 
measurements to be reported.
    (d) Field strength measurements shall be made, to the extent 
possible, on an open field site. Test sites other than open field sites 
may be employed if they are properly calibrated so that the measurement 
results correspond to what would be obtained from an open field site. In 
the case of equipment for which measurements can be performed only at 
the installation site, such as perimeter protection systems, carrier 
current systems, and systems employing a ``leaky'' coaxial cable as an 
antenna, measurements for verification or for obtaining a grant of 
equipment authorization shall be performed at a minimum of three 
installations that can be demonstrated to be representative of typical 
installation sites.
    (e) For intentional radiators, measurements of the variation of the 
input power or the radiated signal level of the fundamental frequency 
component of the emission, as appropriate, shall be performed with the 
supply voltage varied between 85% and 115% of the nominal rated supply 
voltage. For battery operated equipment, the equipment tests shall be 
performed using a new battery.
    (f) To the extent practicable, the device under test shall be 
measured at the distance specified in the appropriate rule section. The 
distance specified corresponds to the horizontal distance between the 
measurement antenna and the closest point of the equipment under test, 
support equipment or interconnecting cables as determined by the 
boundary defined by an imaginary straight line periphery describing a 
simple geometric configuration enclosing the system containing the 
equipment under test. The equipment under test, support equipment and 
any interconnecting cables shall be included within this boundary.
    (1) At frequencies at or above 30 MHz, measurements may be performed 
at a distance other than what is specified provided: measurements are 
not made in the near field except where it can be shown that near field 
measurements are appropriate due to the characteristics of the device; 
and it can be demonstrated that the signal levels needed to be measured 
at the distance employed can be detected by the measurement equipment. 
Measurements shall not be performed at a distance greater than 30 meters 
unless it can be further demonstrated that measurements at a distance of 
30 meters or less are impractical. When performing measurements at a 
distance other than that specified, the results shall be extrapolated to 
the specified distance using an extrapolation factor of 20 dB/decade 
(inverse linear-distance for field strength measurements; inverse-
linear-distance-squared for power density measurements).
    (2) At frequencies below 30 MHz, measurements may be performed at a 
distance closer than that specified in the regulations; however, an 
attempt should be made to avoid making measurements in the near field. 
Pending the development of an appropriate measurement procedure for 
measurements performed below 30 MHz, when performing measurements at a 
closer distance than specified, the results shall be extrapolated to the 
specified distance by either making measurements at a minimum of two 
distances on at least one radial to determine the proper extrapolation 
factor or by using the square of an inverse linear distance 
extrapolation factor (40 dB/decade).
    (3) The applicant for a grant of certification shall specify the 
extrapolation method used in the application filed with the Commission. 
For equipment subject to Declaration of Conformity or verification, this 
information shall be retained with the measurement data.
[[Page 758]]
    (4) When measurement distances of 30 meters or less are specified in 
the regulations, the Commission will test the equipment at the distance 
specified unless measurement at that distance results in measurements 
being performed in the near field. When measurement distances of greater 
than 30 meters are specified in the regulations, the Commission will 
test the equipment at a closer distance, usually 30 meters, 
extrapolating the measured field strength to the specified distance 
using the methods shown in this section.
    (5) Measurements shall be performed at a sufficient number of 
radials around the equipment under test to determine the radial at which 
the field strength values of the radiated emissions are maximized. The 
maximum field strength at the frequency being measured shall be reported 
in the equipment authorization report. This paragraph shall not apply to 
Access BPL equipment on overhead medium voltage lines. In lieu thereof, 
the measurement guidelines established by the Commission for Access BPL 
shall be followed.
    (g) Equipment under test shall be adjusted, using those controls 
that are readily accessible to or are intended to be accessible to the 
consumer, in such a manner as to maximize the level of the emissions. 
For those devices to which wire leads may be attached by the consumer, 
tests shall be performed with wire leads attached. The wire leads shall 
be of the length to be used with the equipment if that length is known. 
Otherwise, wire leads one meter in length shall be attached to the 
equipment. Longer wire leads may be employed if necessary to 
interconnect to associated peripherals.
    (h) For a composite system that incorporates devices contained 
either in a single enclosure or in separate enclosures connected by wire 
or cable, testing for compliance with the standards in this part shall 
be performed with all of the devices in the system functioning. If an 
intentional radiator incorporates more than one antenna or other 
radiating source and these radiating sources are designed to emit at the 
same time, measurements of conducted and radiated emissions shall be 
performed with all radiating sources that are to be employed emitting. A 
device which incorporates a carrier current system shall be tested as if 
the carrier current system were incorporated in a separate device; that 
is, the device shall be tested for compliance with whatever rules would 
apply to the device were the carrier current system not incorporated, 
and the carrier current system shall be tested for compliance with the 
rules applicable to carrier current systems.
    (i) If the device under test provides for the connection of external 
accessories, including external electrical input signals, the device 
shall be tested with the accessories attached. The device under test 
shall be fully exercised with these external accessories. The emission 
tests shall be performed with the device and accessories configured in a 
manner that tends to produce maximized emissions within the range of 
variations that can be expected under normal operating conditions. In 
the case of multiple accessory external ports, an external accessory 
shall be connected to one of each type of port. Only one test using 
peripherals or external accessories that are representative of the 
devices that will be employed with the equipment under test is required. 
All possible equipment combinations do not need to be tested. The 
accessories or peripherals connected to the device being tested shall be 
unmodified, commercially available equipment.
    (j) If the equipment under test consists of a central control unit 
and an external or internal accessory(ies) (peripheral) and the party 
verifying the equipment or applying for a grant of equipment 
authorization manufactures or assembles the central control unit and at 
least one of the accessory devices that can be used with that control 
unit, testing of the control unit and/or the accessory(ies) must be 
performed using the devices manufactured or assembled by that party, in 
addition to any other needed devices which the party does not 
manufacture or assemble. If the party verifying the equipment or 
applying for a grant of equipment authorization does not manufacture or 
assemble the central control unit and at least one of the accessory
[[Page 759]]
devices that can be used with that control unit or the party can 
demonstrate that the central control unit or accessory(ies) normally 
would be marketed or used with equipment from a different entity, 
testing of the central control unit and/or the accessory(ies) must be 
performed using the specific combination of equipment which is intended 
to be marketed or used together. Only one test using peripherals or 
accessories that are representatve of the devices that will be employed 
with the equipment under test is required. All possible equipment 
combinations are not required to be tested. The accessories or 
peripherals connected to the device being tested shall be unmodified, 
commercially available equipment.
    (k) A composite system is a system that incorporates different 
devices contained either in a single enclosure or in separate enclosures 
connected by wire or cable. If the individual devices in a composite 
system are subject to different technical standards, each such device 
must comply with its specific standards. In no event may the measured 
emissions of the composite system exceed the highest level permitted for 
an individual component. For digital devices which consist of a 
combination of Class A and Class B devices, the total combination of 
which results in a Class A digital device, it is only necessary to 
demonstrate that the equipment combination complies with the limits for 
a Class A device. This equipment combination may not be employed for 
obtaining a grant of equipment authorization or verifying a Class B 
digital device. However, if the digital device combination consists of a 
Class B central control unit, e.g., a personal computer, and a Class A 
internal peripheral(s), it must be demonstrated that the Class B central 
control unit continues to comply with the limits for a Class B digital 
device with the Class A internal peripheral(s) installed but not active.
    (l) Measurements of radio frequency emissions conducted to the 
public utility power lines shall be performed using a 50 ohm/50 uH line-
impedance stabilization network (LISN).
    Note: Receivers tested under the transition provisions contained in 
Sec. 15.37 may be tested with a 50 ohm/5 [mu]H LISN.
    (m) Measurements on intentional radiators or receivers, other than 
TV broadcast receivers, shall be performed and, if required, reported 
for each band in which the device can be operated with the device 
operating at the number of frequencies in each band specified in the 
following table:
------------------------------------------------------------------------
 Frequency range over which device    Number of    Location in the range
              operates               frequencies       of operation
------------------------------------------------------------------------
1 MHz or less......................           1   Middle.
1 to 10 MHz........................           2   1 near top and 1 near
                                                   bottom.
More than 10 MHz...................           3   1 near top, 1 near
                                                   middle and 1 near
                                                   bottom.
------------------------------------------------------------------------
    (n) Measurements on TV broadcast receivers shall be performed with 
the receiver tuned to each VHF frequency and also shall include the 
following oscillator frequencies: 520, 550, 600, 650, 700, 750, 800, 
850, 900 and 931 MHz. If measurements cannot be made on one or more of 
the latter UHF frequencies because of the presence of signals from 
licensed radio stations or for other reasons to be detailed in the 
measurement report, measurements shall be made with the receiver 
oscillator at a nearby frequency. If the receiver is not capable of 
receiving channels above 806 MHz, the measurements employing the 
oscillator frequencies 900 and 931 MHz may be omitted.
    (o) The amplitude of spurious emissions from intentional radiators 
and emissions from unintentional radiators which are attenuated more 
than 20 dB below the permissible value need not be reported unless 
specifically required elsewhere in this part.
    (p) In those cases where the provisions in this section conflict 
with the measurement procedures in paragraph (a) of this section and the 
procedures were implemented after June 23, 1989,
[[Page 760]]
the provisions contained in the measurement procedures shall take 
precedence.
[54 FR 17714, Apr. 25, 1989, as amended at 56 FR 13083, Mar. 29, 1991; 
57 FR 24990, June 12, 1992; 57 FR 33448, July 29, 1992; 58 FR 37430, 
July 12, 1993; 58 FR 51249, Oct. 1, 1993; 61 FR 14502, Apr. 2, 1996; 62 
FR 41881, Aug. 4, 1997; 62 FR 45333, Aug. 27, 1997; 63 FR 36602, July 7, 
1998; 63 FR 42278, Aug. 7, 1998; 65 FR 58466, Sept. 29, 2000; 68 FR 
68545, Dec. 9, 2003; 69 FR 54034, Sept. 7, 2004; 70 FR 1373, Jan. 7, 
2005]



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