Goto Section: 15.29 | 15.32 | Table of Contents
FCC 15.31
Revised as of October 2, 2015
Goto Year:2014 |
2016
§ 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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Goto Section: 15.29 | 15.32
Goto Year: 2014 |
2016
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