CISPR TR 18-1:2017

CISPR TR 18-1 ®
Edition 3.0 2017-10
REDLINE VERSION
TECHNICAL
REPORT
colour
inside
INTERNATIONAL SPECIAL COMMITTEE ON RADIO INTERFERENCE

Radio interference characteristics of overhead power lines and high-voltage
equipment –
Part 1: Description of phenomena

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CISPR TR 18-1 ®
Edition 3.0 2017-10
REDLINE VERSION
TECHNICAL
REPORT
colour
inside
INTERNATIONAL SPECIAL COMMITTEE ON RADIO INTERFERENCE

Radio interference characteristics of overhead power lines and high-voltage

equipment –
Part 1: Description of phenomena

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.100.01 ISBN 978-2-8322-4998-7

– 2 – CISPR TR 18-1:2017 RLV © IEC 2017
CONTENTS
FOREWORD . 5
INTRODUCTION . 2
1 Scope . 9
2 Normative references . 9
3 Terms and definitions . 9
4 Radio noise from HV AC overhead power lines . 10
4.1 General . 10
4.2 Physical aspects of radio noise . 11
4.2.1 Mechanism of formation of a noise field . 11
4.2.2 Definition of noise . 13
4.2.3 Influence of external parameters . 14
4.3 Main characteristics of the noise field resulting from conductor corona . 14
4.3.1 General . 14
4.3.2 Frequency spectrum . 14
4.3.3 Lateral profile . 15
4.3.4 Statistical distribution with varying seasons and weather conditions . 17
5 Effects of corona from conductors . 18
5.1 Physical aspects of corona from conductors . 18
5.1.1 General . 18
5.1.2 Factors in corona generation . 19
5.2 Methods of investigation of corona by cages and test lines . 20
5.2.1 General . 20
5.2.2 Test cages . 20
5.2.3 Test lines . 21
5.3 Methods of predetermination . 22
5.3.1 General . 22
5.3.2 Analytical methods . 22
5.3.3 CIGRÉ method . 22
5.4 Catalogue of standard profiles . 23
5.4.1 General . 23
5.4.2 Principle of catalogue presentation . 23
6 Radio noise levels due to insulators, hardware and substation equipment
(excluding bad contacts) . 25
6.1 Physical aspects of radio noise sources . 25
6.1.1 General . 25
6.1.2 Radio noise due to corona discharges at hardware . 25
6.1.3 Radio noise due to insulators . 25
6.2 Correlation between radio noise voltage and the corresponding field strength
for distributed and individual sources . 27
6.2.1 General . 27
6.2.2 Semi-empirical approach and equation . 27
6.2.3 Analytical methods . 29
6.2.4 Example of application. 30
6.3 Influence of ambient conditions . 30
7 Sparking due to bad contacts . 30
7.1 Physical aspects of the radio noise phenomenon . 30

7.2 Example of gap sources . 32
8 Special d.c. effects Radio noise from HVDC overhead power lines . 32
8.1 General [56, 57] . 32
8.1.1 Description of electric field physical phenomena of HVDC transmission
systems . 32
8.1.2 Description of radio interference phenomena of HVDC transmission
system . 33
8.2 Effects of corona from conductors Physical aspects of DC corona . 34
8.3 Formation mechanism of a noise field from a DC line . 34
8.4 Characteristics of the radio noise from DC lines . 35
8.4.1 General . 35
8.4.2 Frequency spectrum . 35
8.4.3 Lateral profile . 35
8.4.4 Statistical distribution . 35
8.5 Factors influencing the radio noise from DC lines . 36
8.5.1 General . 36
8.5.2 Conductor surface conditions. 36
8.5.3 Conductor surface gradient . 37
8.5.4 Polarity . 37
8.5.5 Weather conditions . 37
8.5.6 Subjective effects . 39
8.6 Calculation of the radio noise level due to conductor corona . 39
8.7 Radio noise due to insulators, hardware and substation equipment . 41
8.8 Valve firing effects . 41
9 Figures . 32
Annex A (informative) Calculation of the voltage gradient at the surface of a conductor
of an overhead line . 55
Annex B (informative) Catalogue of profiles of radio noise field due to conductor
corona for certain types of power line . 59
Annex C (informative) Summary of the catalogue of radio noise profiles according to
the recommendations of the CISPR . 75
Bibliography . 77

Figure 1 – Typical lateral attenuation curves for high voltage lines, normalized to a
lateral distance of y = 15 m, distance in linear scale . 43
Figure 2 – Typical lateral attenuation curves for high voltage lines, normalized to a
direct distance of D = 20 m, distance in logarithmic scale . 44
Figure 3 – Examples of statistical yearly distributions of radio-noise levels recorded
continuously under various overhead lines . 45
Figure 4 – Examples of statistical yearly distributions of radio-noise levels recorded
continuously under various overhead lines . 46
Figure 5 – Example of statistical yearly distributions of radio-noise levels recorded
continuously under various overhead lines . 47
Figure 6 – Examples of statistical yearly distributions of radio-noise levels recorded
continuously under various overhead lines . 48
Figure 7 – Equipotential lines for clean and dry insulation units . 49
Figure 8 – Determination of the magnetic field strength from a perpendicular to a
section of a line, at a distance x from the point of injection of noise current I . 49
Figure 9 – Longitudinal noise attenuation versus distance from noise source (from test
results of various experiments frequencies around 0,5 MHz) . 50

– 4 – CISPR TR 18-1:2017 RLV © IEC 2017
Figure 10 – Lateral profile of the radio noise field strength produced by distributed
discrete sources on a 420 kV line of infinite length . 51
Figure 11 – Impulsive radio-noise train of gap-type discharges . 52
Figure 12 – Example of relative strength of radio noise field as a function of frequency
below 1 GHz using QP detector . 52
Figure 13 – Example of relative strength of radio noise field due to gap discharge as a
function of frequency 200 MHz to 3 GHz using peak detector . 53
Figure 14 – Example of relative strength of radio noise field as a function of the
distance from the line. 53
Figure 15 – Unipolar and bipolar space charge regions of a HVDC transmission line . 54
Figure 16 – The corona current and radio interference field . 54
Figure B.1 – Triangular formation (1) . 60
Figure B.2 – Triangular formation (2) . 61
Figure B.3 – Flat formation . 62
Figure B.4 – Arched formation . 63
Figure B.5 – Flat wide formation . 64
Figure B.6 – Vertical formation (480 (Rail) X 4B) . 65
Figure B.7 – Flat formation . 66
Figure B.8 – Flat formation . 67
Figure B.9 – Arched formation . 68
Figure B.10 – Flat formation . 69
Figure B.11 – Arched formation . 70
Figure B.12 – Flat formation . 71
Figure B.13 – Vertical formation (480 (Cardinal) X 6B) . 72
Figure B.14 – Typical frequency spectra for the radio noise fields of high voltage
power lines . 73
Figure B.15 – Prediction of radio noise level of a transmission line for various types of
weather . 74
Figure C.1 – Examples of transformations of the profiles of Figures B.1 to B.13 using
the direct distance of 20 m as reference . 76

Table B.1 – List of profiles . 59
Table C.1 – Radio noise profiles . 75

INTERNATIONAL ELECTROTECHNICAL COMMISSION
INTERNATIONAL SPECIAL COMMITTEE ON RADIO INTERFERENCE
____________
RADIO INTERFERENCE CHARACTERISTICS
OF OVERHEAD POWER LINES AND
HIGH-VOLTAGE EQUIPMENT –
Part 1: Description of phenomena

FOREWORD
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5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
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6) All users should ensure that they have the latest edition of this publication.
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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.
This redline version of the official IEC Standard allows the user to identify the changes
made to the previous edition. A vertical bar appears in the margin wherever a change
has been made. Additions are in green text, deletions are in strikethrough red text.

– 6 – CISPR TR 18-1:2017 RLV © IEC 2017
The main task of IEC technical committees is to prepare International Standards. However, a
technical committee may propose the publication of a technical report when it has collected
data of a different kind from that which is normally published as an International Standard, for
example "state of the art".
CISPR 18-1, which is a technical report, has been prepared by CISPR subcommittee B:
Interference relating to industrial, scientific and medical radio-frequency apparatus, to other
(heavy) industrial equipment, to overhead power lines, to high voltage equipment and to
electric traction.
This third edition cancels and replaces the second edition published in 2010. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) updated description of the RF characteristics of spark discharges which might contain
spectral radio noise components up to the GHz frequency range;
b) addition of state of the art in HVDC converter technology
The text of this technical report is based on the following documents:
DTR Report on voting
CIS/B/653/DTR CIS/B/674/RVDTR
Full information on the voting for the approval of this technical report 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.
A list of all parts of the CISPR 18 series can be found, under the general title Radio
interference characteristics of overhead power lines and high-voltage equipment, on the IEC
website.
The committee has decided that the contents of this publication will remain unchanged until
the stability 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.
A bilingual version of this publication may be issued at a later date.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
INTRODUCTION
This Technical Report is the first of a three-part series dealing with radio noise generated by
electrical power transmission and distribution facilities (overhead lines and substations). It
contains information in relation of the physical phenomena involved in the generation of
electromagnetic noise fields. It also includes a description of the main properties of such
fields and their numerical values. Its content was adjusted such as to allow for use of the
lateral distance y for the establishment of standard profiles for the lateral radio noise field
emanating from HV overhead power lines.
The technical data given in this Part 1 of the CISPR 18 series are intended to be a useful aid
to overhead line designers and also to anyone concerned with checking the radio noise
performance of a line to ensure satisfactory protection of wanted radio signals. The data
should facilitate the use of the recommendations given in its Parts 2 and 3 dealing with
– methods of measurement and procedures for determining limits, and a
– code of practice for minimizing the generation of radio noise.
The CISPR 18 series does not deal with biological effects on living matter or any issues
related to exposure to electromagnetic fields.
This document has been prepared in order to provide information on the many factors
involved in protecting the reception of radio, especially (but not limited to) analogue television,
and digital terrestrial television broadcasting, hereafter denominated as digital television
broadcasting, from interference due to background noise generated by AC and DC high
voltage overhead power lines, distribution lines, and associated equipment. The information
given should be of assistance when means of avoiding or abating radio noise are being
considered.
Information is mainly given on the generation and characteristics of radio noise from
AC power lines and equipment operating at 1 kV and above, in the frequency ranges
0,15 MHz to 30 MHz (a.m. sound broadcasting), 30 MHz to 300 MHz (f.m. sound broadcasting,
analogue television broadcasting) and in the range 470 MHz to 950 MHz (digital television
broadcasting). The special aspect of spark discharges due to bad contacts or defects is taken
into account. Information is also given on interference due to DC overhead power lines for
which corona and interference conditions are different from those of AC power lines. The
radio broadcast services mentioned above are examples only and the information in this
document relates, in a technology-neutral way, to protection of radio reception in general, for
the given frequency ranges.
The general procedure for establishing the limits of the radio noise from overhead power lines
and associated equipment is given, together with typical values as examples, and methods of
measurement.
The clause on limits for conductor corona, which may occur in normal operation of power lines,
concentrates on the low frequency and medium frequency bands as it is only in these bands
where ample evidence, based on established practice, is available. Examples of limits to
protect radio reception in the frequency band 30 MHz to 300 MHz are not given, as measuring
methods and certain other aspects of the problems in this band have not yet been fully
resolved. Site measurements and service experience have shown that levels of noise from
power lines generated by conductor corona at frequencies higher than 300 MHz are so low
that interference is unlikely to be caused to analogue television reception.
Presently, there are no limits for radio noise due to spark discharges, which may occur at bad
contacts or on the surface of polluted insulators, to protect radio reception in the UHF band
(around 470 MHz to 950 MHz) for digital television broadcasting. The characteristics of spark
discharges in the UHF band are not fully understood yet. Furthermore, digital television
systems employ error-correction functions, and the true effects of spark discharges to image
quality are consequently not quite known.

– 8 – CISPR TR 18-1:2017 RLV © IEC 2017
The values of limits given as examples are calculated to provide a reasonable degree of
protection to the reception of e.g. radio broadcasting at the edges of the recognized service
areas of the appropriate transmitters in the a.m. radio frequency bands, in the least
favourable conditions likely to be generally encountered. These limits are intended to provide
guidance at the planning stage of the line and national standards or other specifications
against which the performance of the line may be checked after construction and during its
useful life.
Recommendations are made on the design, routing, construction and maintenance of the lines
and equipment forming part of the power distribution system to minimize interference and it is
hoped that this document will aid other radio services in the consideration of the problems of
interference.
RADIO INTERFERENCE CHARACTERISTICS
OF OVERHEAD POWER LINES AND
HIGH-VOLTAGE EQUIPMENT –
Part 1: Description of phenomena

1 Scope
This part of CISPR 18, which is a Technical Report, applies to radio noise from overhead
power lines, associated equipment, and high-voltage equipment which may cause interference
to radio reception. The scope of this document includes the causes, measurement and effects
of radio interference, design aspects in relation to this interference, methods and examples
for establishing limits and prediction of tolerable levels of interference from high voltage
overhead power lines and associated equipment, to the reception of radio broadcast signals
and services.
The frequency range covered is 0,15 MHz to 300 MHz 3 GHz.
Radio frequency interference caused by the pantograph of overhead railway traction systems
is not considered in this document.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. 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:
Electromagnetic compatibility
CISPR 16-1-1, Specification for radio disturbance and immunity measuring apparatus and
methods – Part 1-1: Radio disturbance and immunity measuring apparatus – Measuring
apparatus
CISPR TR 18-2:2010__ , Radio interference characteristics of overhead power lines and
high-voltage equipment – Part 2: Methods of measurement and procedure for determining
limits
ISO IEC Guide 99, International vocabulary of metrology – Basic and general concepts and
associated terms (VIM)
NOTE Informative references are listed in the Bibliography.
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-161 and the
ISO IEC Guide 99 apply.
_______________
Under preparation. Stage at the time of publication: CISPR/RPUB 18-2:2017.

– 10 – CISPR TR 18-1:2017 RLV © IEC 2017
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
4 Radio noise from HV AC overhead power lines
4.1 General
Radio noise from high voltage alternating current (HVAC), which is to say above 1 kV,
overhead power lines may be generated over a wide band of frequencies by
a) corona discharges in the air at the surfaces of conductors, insulator assemblies and
hardware;
b) discharges and sparking at highly stressed areas of insulators;
c) sparking at loose or imperfect contacts of and at defects in hardware (cracks, rust).
The sources of a) and b) are usually distributed along the length of the line, but source c) is
usually local. For lines operating above about 100 kV, the electric stress in the air at the
surface of conductors and hardware can cause corona discharges. Sparking at bad contacts
or broken or cracked insulators can give rise to local sources of radio noise. High voltage
apparatus in substations may also generate radio noise which can be propagated along the
overhead lines.
If the field strength of the radio noise at the antennas used for receiving broadcast sound and
television services radio reception is too high, it can cause degradation of the sound output
and, in the case of television, the picture also quality and performance of the respective radio
communication or broadcast service and application.
The generation of radio noise is affected by weather conditions, for example, conductor
corona is more likely to occur in wet weather because of the water droplets which form on the
conductors whereas, under these conditions, bad contacts can become bridged with water
droplets and the generation of radio noise, by this process, ceases. Consequently, loose or
imperfect contacts are more likely to spark in dry weather conditions. Dry, clean insulators
may cause interference in fair weather, but prolonged sparking on the surfaces of insulators is
more likely to occur when they are polluted, particularly during wet, foggy or icy conditions.
For interference-free reception of radio and television signals, it is important that a sufficiently
high ratio is available at the input to the receiver between the level of the wanted signal and
the level of the unwanted radio noise. Interference may therefore be experienced when the
signal strength is low and the weather conditions are conducive to the generation of radio
noise.
Unlike analogue radio reception, to realize interference-free reception of digital signals, it is
important to keep the bit error rate (BER, BER used to evaluate digital communication quality)
-2
below a certain value, for example, below around 10 in the front of Viterbi decoder in case
-2
of a ISDB-T system. In this regard, a BER of around 10 in the front of Viterbi decoder

-8
assures a BER below 10 at the input of a display by error-correction function, which is
commonly employed in modern digital communication systems.
When investigating radio noise it should be borne in mind that the local field may be caused
by a distant source or sources as the noise may propagate along the line without substantial
losses, over a considerable distance.

4.2 Physical aspects of radio noise
4.2.1 Mechanism of formation of a noise field
4.2.1.1 General
Corona discharges on conductors, insulators or line hardware or sparking at bad contacts can
be the source of radio noise as they inject current pulses into the line conductors. These
propagate along the conductors in both directions from the injection point. The various
components of the frequency spectrum of these pulses have different effects.
In the frequency range 0,15 MHz to a few megahertz, the noise is largely the result of the
effect of propagation along the line. Direct electromagnetic radiation from the pulse sources
themselves does not materially contribute to the noise level. In this case, the wavelength is
long in comparison with the clearances of the conductors and thus the line is not an efficient
radiator. However, associated with each spectral voltage and current component, an electric
and a magnetic field propagate along the line. In view of the relatively low attenuation of this
propagation, the noise field is determined by the aggregation of the effects of all the
discharges spread over many kilometres along the line on either side of the reception point. It
should be noted that close to the line the guided field predominates, whereas further from the
line the radiated field predominates. The changeover is not abrupt and the phenomenon is not
well known. This effect is not important at low frequencies but is apparent at medium
frequencies.
However, for spectral components above 30 MHz where the wavelengths are close to or less
than the clearance of the line conductors, the noise effects can be largely explained by
antenna radiation theory applied to the source of noise, as there is no material propagation
along the line.
It should be appreciated, however, that 30 MHz does not represent a clear dividing line
between the two different mechanisms producing noise fields.
4.2.1.2 Longitudinal propagation
In the case of a single conductor line mounted above the ground, there is a simultaneous
propagation of a voltage wave U(t) and a current wave I(t).
For a given frequency, the two quantities are related by the expression U(ω) = Z(ω) × I(ω)
where Z, also a function of ω, is the surge impedance of the line.
During propagation the waves are attenuated by a common coefficient α where:
–αx
U = U e
x 0
–αx
I = I e
x 0
where
U and I are the amplitudes at the source, and
0 0
x is the distance of propagation along the line.
In case of multi-phase lines, experience shows that any system of voltages or currents
becomes distorted in propagation, that is to say, the attenuation varies with the distance
propagated and it differs for each conductor. Theory of propagation and actual measurements
on power lines have shown that noise voltages on the phase conductors can be considered as
being made up of a number of "modes", each one having components on every conductor.
One mode propagates between all conductors in parallel and earth. The others propagate

– 12 – CISPR TR 18-1:2017 RLV © IEC 2017
between conductors. Each mode has its own different propagation attenuation. The complete
theory of modal propagation is complex and involves matrix equations outside the scope of
this document. Reference is made here to CIGRÉ and other published works. It is important to
note that the attenuation of the conductor-to-earth mode propagation is fairly high, that is to
say 2 dB/km to 4 dB/km, while the attenuation of the various conductor-to-conductor modes is
a small fraction of 1 dB/km at a frequency of 0,5 MHz.
4.2.1.3 Electromagnetic field
The radio noise voltages and currents propagating along the line produce an associated
propagating electromagnetic field near the line.
It should be noted here that in free space the electric and magnetic components of the field
associated with radiated electromagnetic waves are at right angles both to each other and to
the direction of propagation. The ratio of their amplitudes represents a constant value:
E
(V/m)
= 377Ω
H
(A/m)
and is called the intrinsic impedance or impedance of free space.
On the other hand, the fields near the line are related to the radio frequency voltages and
currents propagating along the line and their ratio depends on the surge impedance of the line
for the various modes. Furthermore, the directions of the electric and magnetic field
components differ from those for radiated fields in free space as they are largely determined
by the geometrical arrangements of the line conductors. The matter is further complicated by
the fact that soil conditions affect differently the mirror image in the ground of the electric and
magnetic field components, respectively.
The electric field strength E(y) at ground level of a single conductor line, which is the vertical
component of the total electric field strength, can be predicted by the following empirical
equation that has, in a lot of cases, proven to give a good approximation:
h
E(y ) = 120 I
2 2
h + y
where
I is the radio noise current, in A, propagating in the conductor;
h is the height above ground, in m, of the conductor;
y is the lateral distance, in m, from a point at ground level directly under the conductor to
the measuring point; and
E is the electric field strength, in V/m.
Furthermore, for an infinitely long single conductor line, the induction zone, or near field, has
the same simple ratio of electric and magnetic field strength as the far field from a radio
transmitter, that is to say 377 Ω, and this is approximately true for all values of ground
conductivity.
In the case of a multi-phase line, the total electric field strength is the vector sum of the
individual field strength components associated with each phase conductor. A more
comprehensive treatment, together with practical methods of assessing the electromagnetic
field, is discussed in 5.3 of CISPR TR 18-2:__ . The equation given above is a simplified
version accurate for a distance of D = 20 m and f = 0,5 MHz where D is the direct distance, in
_______________
Under preparation. Stage at the time of publication: CISPR/RPUB 18-2:2017.

m, between the measuring antenna and the nearest conductor of the line, and f is the
measurement frequency. For conventional power transmission lines (i.e. with a conductor
height above ground which is less than 15 m), this direct distance D approximately
corresponds to a lateral distance y of 15 m. For a wider range of D and f, it would be
necessary to take into account all the parameters affecting the equation.
4.2.1.4 Aggregation effect
In the case of uniformly distributed noise sources, the field strength generated by a unit length
of a phase conductor can be expressed at any point along the line as a function of the
longitudinal distance x and the lateral distance y, that is to say, E(y,x). At a given lateral
distance of y,
−αx
E (y,x) = E (y)e
The random pulses on a long line with uniformly distributed noise sources combine together
to form the total field. The manner in which they combine is not unanimously agreed upon.
Some investigators consider that they combine quadratically:
∞
2 2 −2αx
E (y) = 2 E (y)e dx
∫
E
E (y) =
or .
α
Other investigators believe that, if a quasi-peak detector is used to measure the field strength,
the individual pulses do not add and others have obtained results between the two extremes.
This disagreement is only important in analytical prediction methods, the results obtained by
the different methods vary by only 1 dB or 2 dB.
In case of multi-phase lines, the calculation follows the sample principle but is complicated by
the presence of several modes, each mode having a different attenuation coefficient. A more
detailed discussion, with examples of calculation, is given in Clause 6.
4.2.2 Definition of noise
The instantaneous value of the noise varies continuously and in a random manner, but its
average power level over a sufficiently long period, for example, 1 s, gives a stationary
random quantity which can be measured. Another quantity suitable for measurement is the
peak or some weighted peak value of the noise level.
A noise measuring instrument is basically a tuneable selective and sensitive voltmeter with a
specified pass-band. When connecting to a suitable rod or loop antenna and properly
calibrated, it can measure the electric or magnetic component of the noise field. For
measurements of the magnetic component of the noise field in the frequency range up to
30 MHz, normally a loop antenna is used. For measurements of the electric component of the
noise field in the frequency range above 30 MHz, use of a biconical antenna is recommended.
Depending on the design of the measuring receiver, the noise level can be measured in terms
of RMS, peak or quasi-peak values. The RMS value defines the noise in terms of energy.
Many types of noise from electrical equipment, as well as noise due to power-line corona,
consist of a succession of short pulses with approximately stable repetition
...