Goto Section: 15.29 | 15.32 | Table of Contents
Revised as of October 26, 2020
Goto Year:2020 |
§ 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).
Note 1 to paragraph (a)(4): Digital devices tested to show compliance
with the provisions of § 15.109(g)(2) must be tested following the ANSI
C63.4-2014 procedure described in paragraph (a)(4) 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. 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
Supplier's Declaration of Conformity.
(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 area test site. Test sites other than open area test sites
may be employed if they are properly calibrated so that the measurement
results correspond to what would be obtained from an open area test
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 Supplier's Declaration of Conformity 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
(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 Supplier's Declaration of Conformity, 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) A composite system, as defined in § 2.947(f) of this chapter, that
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
declaring compliance of 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 declaring
compliance of 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 representative 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) Composite systems (i.e., systems that incorporate different devices
contained in a single enclosure or in separate enclosures connected by
wire or cable) shall be measured for compliance with the technical
standards of this part in accordance with the procedures in § 2.947(f)
of this chapter. For digital devices that 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 declaring compliance of 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
(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
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
(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; 82 FR 50831 , Nov. 2, 2017]
Goto Section: 15.29 | 15.32
Goto Year: 2020 |
CiteFind - See documents on FCC website that
cite this rule
Want to support this service?
Report errors in
this rule. Since these rules are converted to HTML by machine, it's possible errors have been made. Please
help us improve these rules by clicking the Report FCC Rule Errors link to report an error.
Helping make public information public