CISPR 12:2007

INTERNATIONAL
CISPR
ELECTROTECHNICAL
COMMISSION
COMMISSION
Sixth edition
ÉLECTROTECHNIQUE
Sixième édition
2007-05
INTERNATIONALE
INTERNATIONAL SPECIAL COMMITTEE ON RADIO INTERFERENCE
COMITÉ INTERNATIONAL SPÉCIAL DES PERTURBATIONS RADIOÉLECTRIQUES
Vehicles, boats and internal combustion engines –
Radio disturbance characteristics –
Limits and methods of measurement for the
protection of off-board receivers

Véhicules, bateaux et
moteurs à combustion interne –
Caractéristiques de perturbation radioélectrique –
Limites et méthodes de mesure pour la protection
des récepteurs extérieurs
Reference number
Numéro de référence
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INTERNATIONAL
CISPR
ELECTROTECHNICAL
COMMISSION
COMMISSION
Sixth edition
ÉLECTROTECHNIQUE
Sixième édition
2007-05
INTERNATIONALE
INTERNATIONAL SPECIAL COMMITTEE ON RADIO INTERFERENCE
COMITÉ INTERNATIONAL SPÉCIAL DES PERTURBATIONS RADIOÉLECTRIQUES
Vehicles, boats and internal combustion engines –
Radio disturbance characteristics –
Limits and methods of measurement for the
protection of off-board receivers

Véhicules, bateaux et
moteurs à combustion interne –
Caractéristiques de perturbation radioélectrique –
Limites et méthodes de mesure pour la protection
des récepteurs extérieurs
PRICE CODE
XA
Commission Electrotechnique Internationale CODE PRIX
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
For price, see current catalogue
Pour prix, voir catalogue en vigueur

– 2 – CISPR 12 © IEC:2007
CONTENTS
FOREWORD.5
INTRODUCTION.7

1 Scope.8
2 Normative references .9
3 Terms and definitions .9
4 Limits of disturbance .11
4.1 Determination of conformance of vehicle/boat/device with limits.11
4.2 Peak and quasi-peak detector limits .13
4.3 Average detector limit.13
5 Methods of measurement .14
5.1 Measuring instrument .14
5.1.1 Spectrum analyser parameters .15
5.1.2 Scanning receiver parameters .15
5.1.3 Antenna types .16
5.1.4 Accuracy .16
5.2 Measuring location requirements .17
5.2.1 Outdoor test site (OTS) requirements .17
5.2.2 Absorber lined shielded enclosure (ALSE) requirements.19
5.2.3 Antenna requirements .20
5.3 Test object conditions.22
5.3.1 General .22
5.3.2 Vehicles and boats .22
5.3.3 Devices .23
5.4 Data collection .24
6 Methods of checking for compliance with CISPR requirements .24
6.1 General .24
6.2 Application of limit curves.24
6.2.1 Measurements under dry conditions .24
6.2.2 Measurements under wet conditions.24
6.3 Evaluation (general) .25
6.4 Type approval test.25
6.4.1 Single sample.25
6.4.2 Multiple samples (optional) .25
6.5 Surveillance (quality audit) of series production.25
6.5.1 Single sample.25
6.5.2 Multiple samples (optional) .25
6.6 Quick prototype check for development testing (optional, quasi-peak detector
emissions only) .

Annex A (normative) Statistical analysis of the results of measurements .26
Annex B (normative) Procedure to determine an alternative emission limit for
measurements at 3 m antenna distance.28

CISPR 12 © IEC:2007 – 3 –
Annex C (informative) Antenna and transmission line maintenance and
characterization .30
Annex D (informative) Construction features of motor vehicles affecting the emission
of ignition noise .35
Annex E (informative) Measurement of the insertion loss of ignition noise suppressors.36
Annex F (informative) Methods of measurement to determine the attenuation
characteristics of ignition noise suppressors for high voltage ignition systems .42
Annex G (informative) Flow chart for checking the applicability of CISPR 12.52
Annex H (informative) Items under consideration .53

Bibliography.54

Figure 1 – Method of determination of conformance.12
Figure 2 – Limit of disturbance (peak and quasi-peak detector) at 10 m antenna
distance.13
Figure 3 – Limits of disturbance (average detector) at 10 m antenna distance .14
Figure 4 – Measuring site (OTS) for vehicles and devices.18
Figure 5 – Measuring site (OTS) for boats .19
Figure 6 – Antenna position to measure emissions – Vertical polarization.20
Figure 7 – Antenna position to measure emissions – Horizontal polarization.21
Figure B.1 – Determination of the maximum antenna angle.28
Figure B.2 – Calculation of the resulting gain reduction a.29
Figure C.1 – Alternate antenna factor determination (10 m antenna distance).34
Figure E.1 – Test circuit.38
Figure E.2 – General arrangement of the test box.38
Figure E.3 – Details of the test box lid .39
Figure E.4 – Details of the test box .39
Figure E.5 – Straight spark-plug ignition noise suppressor (screened or unscreened) .40
Figure E.6 – Right-angle spark-plug ignition noise suppressor (screened or
unscreened).40
Figure E.7 – Noise suppression spark-plug .40
Figure E.8 – Resistive distributor brush .40
Figure E.9 – Noise suppressor in distributor cap .41
Figure E.10 – Noise suppression distributor rotor.41
Figure E.11 – Noise suppression ignition cable (resistive or reactive) .41
Figure F.1 – Test set-up, side view .44
Figure F.2 – Test set-up, top view.45
Figure F.3 – Pressure chamber with ventilation.46
Figure F.4 – Top view of the set-up of a right-angle ignition noise suppressor for
distributors.47
Figure F.5 – Location of high voltage ignition components .48
Figure F.6 – Top view of the test set-up for distributor rotors .49

– 4 – CISPR 12 © IEC:2007
Figure F.7 – Side view of the test set-up for ready-to-use resistive ignition cables .50

Table 1 – Spectrum analyser parameters.15
Table 2 – Scanning receiver parameters .15
Table 3 – Internal combustion engine operating speeds.23
Table A.1 – Statistical factors .26
Table A.2 – Example of frequency sub-bands .27
Table F.1 – Limits .42

CISPR 12 © IEC:2007 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION

INTERNATIONAL SPECIAL COMMITTEE ON RADIO INTERFERENCE
____________
VEHICLES, BOATS AND INTERNAL COMBUSTION ENGINES –
RADIO DISTURBANCE CHARACTERISTICS –
LIMITS AND METHODS OF MEASUREMENT FOR THE PROTECTION
OF OFF-BOARD RECEIVERS
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
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with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard CISPR 12 has been prepared by CISPR subcommittee D:
Electromagnetic disturbances related to electric/electronic equipment on vehicles and internal
combustion powered devices.
This sixth edition cancels and replaces the fifth edition published in 2001 and its Amendment
1 (2005). This edition constitutes a technical revision.
The following changes were made with respect to the previous edition:
– deletion of narrowband / broadband determination
– general improvement of wording

– 6 – CISPR 12 © IEC:2007
The text of this standard is based on the following documents:
Enquiry draft Report on voting
CISPR/D/322CDV CISPR/D/341/RVC

Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
CISPR 12 © IEC:2007 – 7 –
INTRODUCTION
There is a specific need for standards to define acceptable radio frequency performance of all
electrical/electronic products. CISPR 12 has been developed to serve the road vehicle and
related industries with test methods and limits that provide satisfactory protection for radio
reception.
CISPR 12 has been used for many years as a regulatory requirement in numerous countries,
to provide protection for radio receivers in the residential environment. It has been extremely
effective in protecting the radio environment outside the vehicle.

– 8 – CISPR 12 © IEC:2007
VEHICLES, BOATS AND INTERNAL COMBUSTION ENGINES –
RADIO DISTURBANCE CHARACTERISTICS –
LIMITS AND METHODS OF MEASUREMENT FOR THE PROTECTION
OF OFF-BOARD RECEIVERS
1 Scope
Residential Environment
The limits in this International Standard are
designed to provide protection for broadcast
receivers in the frequency range of 30 MHz
to 1 000 MHz when used in the residential
environment. Compliance with this standard
may not provide adequate protection for new
types of radio transmissions or receivers
used in the residential environment nearer
than 10 m to the vehicle, boat or device.
NOTE 1 Experience has shown that compliance with
this standard may provide satisfactory protection for

receivers of other types of transmissions when used in
the residential environment, including radio
transmissions in frequency ranges other than that
specified.
This standard applies to the emission of electromagnetic energy which may cause
interference to radio reception and which is emitted from
a) vehicles propelled by an internal combustion engine, electrical means or both (see 3.1);
b) boats propelled by an internal combustion engine, electrical means or both (see 3.2).
Boats are to be tested in the same manner as vehicles except where they have unique
characteristics as explicitly stated in this standard;
c) devices equipped with internal combustion engines (see 3.3).
See Annex G for a flow chart to help determine the applicability of CISPR 12.
This standard does not apply to aircraft, traction systems (railway, tramway and electric trolley
bus), or to incomplete vehicles. In the case of a dual-mode trolley bus (e.g. propelled by
power from either a.c./d.c. mains or an internal combustion engine), the internal combustion
propulsion system must be included, but the a.c./d.c. mains portion of the vehicle propulsion
system is excluded from this standard.
NOTE 2 Protection of receivers used on board the same vehicle as the disturbance source(s) are covered by
CISPR 25.
The measurement of electromagnetic disturbances while the vehicle is connected to power
mains for charging is not covered in this standard. The user is referred to appropriate IEC and
CISPR standards which define measurement techniques and limits for this condition.
Annex H lists work being considered for future revisions.

CISPR 12 © IEC:2007 – 9 –
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 60050-161, International Electrotechnical Vocabulary (IEV) – Chapter 161: Electro-
magnetic compatibility
CISPR 16-1-1:2006, Specification for radio disturbance and immunity measuring apparatus
and methods – Part 1-1: Radio disturbance and immunity measuring apparatus – Measuring
apparatus
CISPR 16-1-3:2004, Specification for radio disturbance and immunity measuring apparatus
and methods – Part 1-3: Radio disturbance and immunity measuring apparatus – Ancillary
equipment – Disturbance power
CISPR 16-1-4:2007, Specification for radio disturbance and immunity measuring apparatus
and methods – Part 1-4: Radio disturbance and immunity measuring apparatus – Ancillary
equipment – Radiated disturbances
CISPR 16-2-3:2006, Specification for radio disturbance and immunity measuring apparatus
and methods – Part 2-3: Methods of measurement of disturbances and immunity – Radiated
disturbance measurements
CISPR 25, Radio disturbance characteristics for the protection of receivers used on board
vehicles, boats, and on devices – Limits and methods of measurement
3 Terms and definitions
For the purpose of this document, the terms and definitions contained in IEC 60050-161 as
well as the following apply.
3.1
vehicle
machine operating on land which is intended to carry persons or goods
NOTE Vehicles include, but are not limited to, cars, trucks, buses, mopeds, agricultural machinery, earth-moving
machinery, material-handling equipment, mining equipment and snowmobiles.
3.2
boat
vessel intended to be used on the surface of water, its length being no greater than 15 m
3.3
device
machine driven by an internal combustion engine which is not primarily intended to carry
persons or goods
NOTE Devices include, but are not limited to, chainsaws, irrigation pumps, snow blowers, air compressors, and
landscaping equipment
3.4
impulsive ignition noise
unwanted emission of electromagnetic energy, predominantly impulsive in content, arising
from the ignition system within a vehicle, boat or device

– 10 – CISPR 12 © IEC:2007
3.5
ignition noise suppressor
that portion of a high-voltage ignition circuit intended to limit the emission of impulsive ignition
noise
3.6
outdoor test site (OTS)
measurement site similar to an open area test site as specified in CISPR 16, however a
ground plane is not required and there are dimensional changes
NOTE Specific requirements are defined in this document.
3.7
resistive distributor brush
resistive pick-up brush in an ignition distributor cap
3.8
frequency sub-band
segment of the frequency spectrum (30 MHz to 1 000 MHz) defined to enable statistical
evaluation of the test data acquired by swept frequency testing
3.9
representative frequency
assigned frequency of a frequency sub-band to be used for comparison of the data to the limit
3.10
characteristic level
controlling (or dominant) emission level experienced in each frequency sub-band. The
characteristic level is the maximum measurement obtained for both antenna polarizations and
for all the specified measurement positions of the vehicle, boat or device. Known ambient
signals are not considered part of the characteristic level.
3.11
tracking generator
test signal oscillator (continuous wave, cw) that is frequency locked to the receive frequency
of a measuring instrument
3.12
RF disturbance power
RF power measured with a current transformer of an absorbing clamp and an RF measuring
instrument. It may be measured – as the RF disturbance voltage – in a peak or quasi-peak
mode
3.13
spark discharge
in this document, the discharge of energy stored in the ignition coil, in an arc across the
electrodes of a measuring spark-plug
3.14
resistive high-voltage (HV) ignition cable
ignition cable whose conductor has a high resistance (attenuation)
3.15
residential environment
environment having a 10 m protection distance between the source and the point of radio
reception and where the source uses the public low voltage power system or battery power
NOTE Examples of a residential environment include rooming houses, private dwellings, entertainment halls,
theatres, schools, public streets, etc.

CISPR 12 © IEC:2007 – 11 –
4 Limits of disturbance
4.1 Determination of conformance of vehicle/boat/device with limits
In the 30 MHz – 1 GHz frequency range, the vehicle/boat/device shall comply with both:
• average limits when the vehicle/boat/device is in “Key-On, Engine-Off” mode (see 5.3.2.1),
and
• peak or quasi-peak limits when the vehicle/boat/device is in “Engine-Running” mode (see
5.3.2.2)
The limits given in this standard take into account uncertainties.
Figure 1 defines the method for determination of conformance.

– 12 – CISPR 12 © IEC:2007
Start
"Engine- Running mode"
"Key- On, Engine- Off" operating

operating conditions
conditions
Measurement with  Measur ement with
peak detector peak detector
Are the peak       Are the peak
data below the    data below the
(a)
(a)
average limit ? quasi- peak limit ?
Yes Yes
No
No
Are the peak
data below the
peak limit ?
Yes
No
Measurement with
(b)
quasi- peak det ector
Measurement with
(b)
average detector
Are the quasi- peak
data below the
Yes
quasi- peak limit ?
Are the average
data below the
average limit ? Yes
No
No
Pass for "Key-On, Pass for "Engine -
Engine-Off" Running mode"
"Key-On, Engine-Off"
pass AND "Engine-
Running” mode pass ?
No
Yes
Fail Fail
Pass
IEC  706/07
a Because measurement with peak detector is always higher than or equal to measurement with quasi-
peak detector (and average detector respectively) and applicable peak limit is always higher than or
equal to applicable quasi-peak limit (and average limit respectively), this single detector measurement
can lead to a simplified and quicker conformance process.
b This flow-chart is applicable for each individual frequency, e.g only frequencies that are above the
applicable limit need to be remeasured with quasi-peak detector (and average detector respectively).
Figure 1 – Method of determination of conformance

CISPR 12 © IEC:2007 – 13 –
4.2 Peak and quasi-peak detector limits
The limit for emissions measured with peak or quasi-peak detector at 10 m antenna distance
is given in the table of Figure 2 and is shown graphically in Figure 2. Only one of the
bandwidths listed needs to be chosen for testing. For more accurate determination, the
equations given in Figure 2 shall be used. For measurements at 3 m antenna distance, 10 dB
shall be added to the limit.
Limit L in dB (μV/m) as a function of bandwidth, detector and frequency f in MHz
bw
30-75 75-400 400-1000
L
bw Measurement type
MHz MHz MHz
L
120 kHz 34 34 + 15,13 lg (f/75) 45 Quasi-peak
L
120 kHz 65 Peak
54 + 15,13 lg (f/75)
72 + 15,13 lg (f/75)
L  83 Peak
1 MHz 72
Linear when plotted
Quasi-peak Peak
dB versus log frequency
L L L
120 kHz 120 kHz 1 MHz
45 180 65 83
40 100 60 78
Linear plot Linear plot
Linear plot Logarithmic
dB (μV/m) dB (μV/m)
dB (μV/m) plot μV/m
34 50 54 72
30 75 400 1 000
Frequency in MHz - logarithmic plot IEC  707/07

NOTE 1 For vehicles equipped with electric propulsion motors, see 5.3.2.
NOTE 2 For peak measurements, see 5.5.
NOTE 3 The correlation factor between quasi-peak and peak measurements is +20 dB at 120 kHz bandwidth,
based on experimental data accumulated in many countries.
Figure 2 – Limit of disturbance (peak and quasi-peak detector)
at 10 m antenna distance
4.3 Average detector limit
The limit for emissions measured with the average detector at 10 m antenna distance is
shown in Figure 3. Vehicles/boats/devices not including electronic oscillators with an
operating frequency greater than 9 kHz shall be deemed to be in compliance with the average
requirements of this clause without performing tests for emissions with average detector.
Vehicles/boats/devices which meet the average emissions requirements of CISPR 25,
Clause 5 shall also be deemed to be in compliance with the average requirements of this
subclause and no further testing is necessary.

– 14 – CISPR 12 © IEC:2007
For measurements at 3 m antenna distance, 10 dB shall be added to the limit.
Annex D of CISPR 16-2-3 explains the differences between the CISPR AV detector and an AV
detector (complying with CISPR 16-1:1999). For the purpose of this standard either detector
may be used, since the pulse repetition rate for internal combustion engines is above 10 Hz.
NOTE For type-approval testing per 6.4, use of an alternative test method based upon other regulatory standards
is permitted as detailed herein. This alternate type-approval test applies to those vehicles/boats/devices for which
on-board receivers can be installed. If, when measured in accordance with the vehicle test methodology of
CISPR 25 for emissions using an average detector, the signal strength at the vehicle/boat/device broadcast radio
antenna is less than 20 dB (μV) (10 μV) over the frequency range 76 MHz to 108 MHz, then the vehicle/boat/device
can be deemed to comply with the limits for average emissions and no further testing must be required.

230 1 000
30 100
Frequency in  MHz
IEC  708/07
Figure 3 – Limits of disturbance (average detector) at 10 m antenna distance
5 Methods of measurement
5.1 Measuring instrument
The measuring instrument shall comply with the requirements of CISPR 16-1-1. Either manual
or automatic frequency scanning may be used.
NOTE Spectrum analysers and scanning receivers are particularly useful for disturbance measurements. The
peak detection mode of spectrum analysers and scanning receivers provides a display indication which is never
less than the quasi-peak indication for the same bandwidth. It may be convenient to measure emissions using peak
detection because of the faster scan possible than with quasi-peak detection.
When quasi-peak limits are being used, and a peak detector is used for time efficiency, any
peak measurements with results at or above the test limit shall be re-measured using the
quasi-peak detector.
Field strength in  µV/m
Field Strength in  dB (µV/m)
CISPR 12 © IEC:2007 – 15 –
5.1.1 Spectrum analyser parameters
The scan rate of the spectrum analyser shall be adjusted for the CISPR frequency band and
detection mode used. The maximum scan rate shall comply with the requirements of
CISPR 16-2-3.
The bandwidth of the spectrum analyser shall be chosen such that the noise floor is at least
6 dB lower than the limit curve.
NOTE A preamplifier may be used between the antenna and the spectrum analyser in order to achieve the 6 dB
noise floor requirement.
The recommended scan time and bandwidth are listed in Table 1:
Table 1 – Spectrum analyser parameters
Frequency Peak detector Quasi-peak detector Average detector
range
a) b) a)
MHz  Scan time BW Scan time RBW Scan time
RBW
30 to 1 000 100 kHz / 120 kHz 100 ms / MHz 120 kHz 20 s / MHz 100 kHz / 120 kHz 100 ms /MHz
a)
RBW is defined at –3 dB.
b)
BW is defined at –6 dB.
If a spectrum analyser is used for peak measurements, the video bandwidth shall be at least
three times the resolution bandwidth (RBW).
5.1.2 Scanning receiver parameters
The dwell time of the scanning receiver shall be adjusted for the CISPR frequency band and
detection mode used. The minimum dwell time shall comply with the requirements of
CISPR 16-2-3.
The bandwidth of the scanning receiver shall be chosen such that the noise floor is at least
6 dB lower than the limit curve.
NOTE A preamplifier may be used between the antenna and the scanning receiver in order to achieve the 6 dB
noise floor requirement.
The recommended dwell time, maximum step size and bandwidth are listed in Table 2:
Table 2 – Scanning receiver parameters
Peak detector Quasi-peak detector Average detector
Frequency
range
Band- Step Dwell Band- Step Dwell Band- Step Dwell
MHz
a a a
time width size time width size time
width size
30 to 1 000 120 kHz 50 kHz 5 ms 120 kHz 50 kHz 1 s 120 kHz 50 kHz 5 ms
a
For purely broadband disturbances, the maximum frequency step size may be increased up to a value not
greater than the bandwidth value.

– 16 – CISPR 12 © IEC:2007
5.1.3 Antenna types
5.1.3.1 Reference antenna
The antenna shall be a balanced dipole (see CISPR 16-1-4). Free-space antenna factors are
to be used. For frequencies of 80 MHz or above, the antenna shall be resonant in length, and
for frequencies below 80 MHz it shall be the length equal to the 80 MHz resonant length. It
shall be matched to the feeder by a suitable symmetric-asymmetric transformer device.
5.1.3.2 Broadband antennas
Any linearly polarized receiving antenna is permitted, provided that it can be normalized to the
reference antenna.
A broadband antenna shall be used when making measurements with an automated receiving
system using a scanning measuring instrument. Such a broadband antenna is usable for
measuring emission levels (over the frequency spectrum covered by this standard), provided
that its output can be normalized to the output of the reference antenna in the actual test
environment at the actual test site.
When broadband antennas are used, they shall meet the requirements for complex antennas
given in CISPR 16-1-4. Examples of factors to be considered include:
a) the effective aperture area of the antenna, including its polar response (horizontal and
vertical planes).
b) the effect of a phase centre which moves with frequency.
c) the effect of ground reflection characteristics (including multiple ray reflections which may
arise at specific frequencies at about 500 MHz vertical polarization and 900 MHz
horizontal polarization).
See Annex C for alternate antenna characterization.
5.1.4 Accuracy
The measurement system consisting of the antenna, transmission line and the measuring
instrument, but excluding the source and the measuring site, shall measure electric field
strength over the frequency range of 30 MHz to 1 000 MHz with an accuracy of ±3 dB. See
Clause 4 of CISPR 16-1-4. The frequency accuracy shall be better than ±1 %.
NOTE 1 To ensure that the measurements defined in this standard are within the stated tolerances, consideration
should be given to all pertinent characteristics of measuring equipment (for example, frequency and amplitude
stability, image rejection, cross-modulation, overload levels, selectivity, time constants, and signal/noise ratio), as
well as those affecting the antenna and transmission line.
NOTE 2 It is reasonable to expect additional variations in measurements made of an electric field (see C.13)
within the range of 30 MHz to 1 000 MHz. These are caused by variations in ground conductivity and other factors
influencing repeatability.
CISPR 12 © IEC:2007 – 17 –
5.2 Measuring location requirements
5.2.1 Outdoor test site (OTS) requirements
5.2.1.1 OTS for vehicles and devices
The test site shall be a clear area, free from electromagnetic reflecting surfaces within a circle
of minimum radius 30 m measured from a point midway between the vehicle or device and the
antenna. As an exception, the measuring equipment, and test hut or vehicle in which the
measuring equipment is located (when used) may be within the test site, but only in the
permitted region indicated by the crosshatched area of Figure 4.
NOTE The site requirements defined in 5.2.1.1 and Figure 4 are the application of CISPR 16-1-4 to large
automotive objects.
Vehicles and devices smaller than 2 m in length and width may be tested on an OTS with
dimensions corresponding to CISPR 16-1-4, Figures 2 or 3.
5.2.1.2 OTS for boats
The test site shall be a clear area free from electromagnetic reflecting surfaces within a circle
of minimum radius 30 m measured from a point midway between the engine under test and
the antenna. Exceptions for the measuring equipment are specified in 5.2.1.2.1 and also in
5.2.1.2.2. As an exception, the measuring equipment may be within the test site, but only in
the permitted region indicated by the crosshatched area of Figure 5. The test hut or vehicle or
non-metallic boat of test fixture in/on which the measuring equipment is located may be within
the test site.
Boats or engines/motors for boats tested separately shall be tested in salt or fresh water at a
measuring site as shown in Figure 5.
5.2.1.2.1 Land-based measuring equipment
When the measuring equipment is on land, the test hut or vehicle in which the measuring
equipment is located may be within the test site, but only in the permitted region indicated by
the cross-hatched area of Figure 5.
5.2.1.2.2 Water-based measuring equipment
The measuring equipment shall be installed in a non-metallic boat or non-metallic test fixture
which may be within the test site, but only within the permitted region indicated by the cross-
hatched area of Figure 5.
– 18 – CISPR 12 © IEC:2007
Engine midpoint
positioned on normal
from antenna midpoint
Centre of 30 m radius clear area
at midpoint between reference
antenna and EUT
(10,0 ± 0,2) m
Reference antenna
15 m min radius
Permitted region for
measuring equipment (in
hut or vehicle)
IEC  709/07
NOTE The 10,0 m ± 0,2 m dimension may be changed to 3,00 m ± 0,05 m in accordance with 5.2.3.2 and 5.2.3.4.
Figure 4 – Measuring site (OTS) for vehicles and devices
5.2.1.3 Ambient requirements
To ensure that there is no extraneous noise or signals of sufficient magnitude or density to
affect materially the vehicle measurement, ambient measurements shall be taken before and
after the main test, but without the vehicle/boat/device under test running. In both of these
measurements, the ambient noise shall be at least 6 dB below the limits of disturbance given
in Clause 4, excluding intentional radiators. When assessing compliance in accordance with
Clause 6 any emission exceeding the limits shall require investigation to ensure that they are
not attributable to the vehicle/boat/device in order to be excluded.
NOTE For further guidance, see 5.4 of CISPR 16-1-4.

CISPR 12 © IEC:2007 – 19 –
Engine midpoint positioned on
normal from antenna midpoint
Non-metallic boat or non-metallic
test platform (for testing engines
separately)
Outboard installation
Inboard installation
Note - The horizontal distance is from the centre of the reference
antenna to the nearest peripheral part of the marine installation (or
engine if tested separately)
Centre of 30 m radius clear area
(10,0 ± 0,2) m
at midpoint between reference
antenna and EUT
Reference
antenna
Non-metallic boat or
non-metallic test platform (water-
based test site)
15 m radius
15 m min radius
Permitted region for
measuring equipment (in hut
or vehicle)
IEC  710/07
Figure 5 – Measuring site (OTS) for boats
5.2.2 Absorber lined shielded enclosure (ALSE) requirements
5.2.2.1 Correlation
Absorber lined shielded enclosures may be used provided that the results obtained can be
correlated with those obtained using the OTS described in 5.2.1.
NOTE Such chambers have the advantages of all weather testing, controlled environment and improved
repeatability because of stable chamber electrical characteristics.
5.2.2.2 Ambient requirements
The ambient noise level shall be at least 6 dB below the limits of disturbance given in
Clause 4. The ambient level shall be verified periodically or when test results indicate the
possibility of non-compliance.

– 20 – CISPR 12 © IEC:2007
5.2.3 Antenna requirements
At each measurement frequency (including the end frequencies), measurements shall be
taken for horizontal and vertical polarization (see Figures 6 and 7).
Electrical interaction between the antenna elements and the antenna support/guy system
shall be avoided.
Theoretical considerations of antenna and transmission line geometry demand that the
transmission line does not interact electrically with the antenna
...