§ 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 Communications Service (UPCS) devices are to be
   measured for compliance using ANSI C63.17-2013: “American National Standard
   Methods of Measurement of the Electromagnetic and Operational Compatibility
   of Unlicensed Personal Communications Services (UPCS) Devices” (incorporated
   by reference, see § 15.38).

   (3) Other intentional radiators are to be measured for compliance using the
   following  procedure: ANSI C63.10-2013 (incorporated by reference, see
   § 15.38).

   (4) Unintentional radiators are to be measured for compliance using the
   following procedure excluding clauses 4.5.3, 4.6, 6.2.13, 8.2.2, 9, and 13:
   ANSI C63.4-2014 (incorporated by reference, see § 15.38).

   (b) All parties making compliance measurements on equipment subject to the
   requirements of this part are urged to use these measurement procedures. 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) Except as otherwise indicated in § 15.256, 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). This paragraph
   (f) shall not apply to Access BPL devices operating below 30 MHz.

   (3) For Access BPL devices operating below 30 MHz, measurements shall be
   performed at the 30-meter reference distance specified in the regulations
   whenever possible. Measurements may be performed at a distance closer than
   that specified in the regulations if circumstances such as high ambient
   noise  levels  or  geographic limitations are present. When performing
   measurements  at  a distance which is closer than specified, the field
   strength results shall be extrapolated to the specified distance by using
   the square of an inverse linear distance extrapolation factor (i.e., 40
   dB/decade) in conjunction with the slant-range distance defined in § 15.3(hh)
   of  this part. As an alternative, a site-specific extrapolation factor
   derived from a straight line best fit of measurements of field strength in
   dBµV/m vs. logarithmic distance in meters for each carrier frequency, as
   determined  by  a  linear  least  squares  regression calculation from
   measurements for at least four distances from the power line, may be used.
   Compliance  measurements  for  Access BPL and the use of site-specific
   extrapolation factors shall be made in accordance with the Measurement
   Guidelines for Access BPL systems specified by the Commission. Site-specific
   determination of the distance extrapolation factor shall not be used at
   locations where a ground conductor is present within 30 meters if the Access
   BPL signals are on the neutral/grounded line of a power system.

   (4)  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.

   (5) 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.

   (6) 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 positioned and 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 operator, 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 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).

   (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 operates Number of frequencies Location in
   the range 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, the provisions contained in the
   measurement procedures shall take precedence.

   (q)  As  an alternative to § 15.256, a level probing radar (LPR) may be
   certified as an intentional radiator by showing compliance with the general
   provisions for operation under part 15 subpart C of this chapter, provided
   that  the device is tested in accordance with the provisions in either
   paragraphs  (q)(1) or (2) of this section. Compliance with the general
   provisions for an intentional radiator may require compliance with other
   rules in this part, e.g., § § 15.5, 15.31, and 15.35, etc., when referenced.

   (1)  An LPR device intended for installation inside metal and concrete
   enclosures may show compliance for radiated emissions when measured outside
   a representative enclosure with the LPR installed inside, in accordance with
   the measurement guidelines established by the Commission for these devices.
   LPR devices operating inside these types of enclosures shall ensure that the
   enclosure is closed when the radar device is operating. Care shall be taken
   to ensure that gaskets, flanges, and other openings are sealed to eliminate
   signal leakage outside of the structure. The responsible party shall take
   reasonable steps to ensure that LPR devices intended for use in these types
   of enclosures shall not be installed in open-air environments or inside
   enclosures with lower radio-frequency attenuating characteristics (e.g.,
   fiberglass, plastic, etc.). An LPR device approved under this subsection may
   only be operated in the type of enclosure for which it was approved.

   (2) Except as provided in paragraph (q)(1) of this section, an LPR device
   shall be placed in testing positions that ensure the field strength values
   of the radiated emissions are maximized, including in the main beam of the
   LPR antenna.

   [ 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;  76 FR 71908 , Nov. 21,
   2011;  77 FR 4913 , Feb. 1, 2012;  77 FR 43013 , July 23, 2012;  79 FR 12677 ,
   Mar. 6, 2014;  80 FR 2838 , Jan. 21, 2015;  80 FR 33447 , June 12, 2015]

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