Application Note: Measurements On FM Transmitters For Acceptance, Commissioning and Maintenance

Measurements on FM
Transmitters for Acceptance,

Commissioning and
Maintenance
Application Note
Product:
| R&SETL
Despite the advent of advanced digital

transmission methods, analog broadcast-
ing remains highly important. Until now,
measurements on FM transmitters in
connection with acceptance testing, com-
missioning and maintenance required
using a variety of T&M instruments.
The R&S®ETL TV analyzer combines

these instruments' capabilities in a single
unit and can completely replace them.
Now, for the first time, acceptance test
measurements can be conducted on FM
transmitters quickly and easily using just
one compact test instrument. The
R&S®ETL provides the functionalities of a
power meter, spectrum analyzer, audio
generator, FM measurement demodulator,
stereo decoder, audio analyzer and more
in just one box.
Maintenance
Acceptance, Commissioning and
Measurements on FM Transmitters for
Sep-13 – 7BM105_0E
Klaus,Christiane
Contents
1 Overview ................................................................................. 4
2 FM Basics ............................................................................... 6
2.1 The Multiplex (MPX) Signal .........................................................................6
2.1 Pre- and Deemphasis ...................................................................................8
2.2 RF Bandwidth ...............................................................................................8
2.3 Stereo Decoder .............................................................................................8
2.4 Transmitter Inputs ........................................................................................9
3 R&S®ETL Settings for FM Measurements .......................... 10

3.1 General FM Settings – Radio Settings .....................................................11
3.1.1 Modulation Standard ....................................................................................12
3.1.2 Stereo Decoder ............................................................................................13
3.1.3 Outputs .........................................................................................................14
3.1.4 Universal Interface (Option B201) ................................................................15
3.1.5 DUT Parameters...........................................................................................15
3.2 Audio Generator Settings ..........................................................................16
3.2.1 Type ..............................................................................................................17
3.2.2 Signal ............................................................................................................18
3.2.3 Connector Config .........................................................................................19
3.2.4 Waveform .....................................................................................................19
3.2.5 Ampl Definition and Level .............................................................................20
3.2.6 Preemphasis/Preemphasis Compensation ..................................................20
3.3 Configuration Dialogs for Audio Analysis Measurements ....................21
3.3.1 Demodulator .................................................................................................21
3.3.2 Audio Generator ...........................................................................................22
3.3.3 Measurement Options ..................................................................................22
3.4 Configuration Dialogs for Modulation Analysis Measurements ...........22
4 Preparatory Steps ................................................................ 23

4.1 Required Equipment ..................................................................................23
4.2 Test Setup ...................................................................................................23
4.3 Protection Against Destructive Input Power ...........................................25
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4.4 R&S ETL Default Configuration for Measurements ...............................25
7BM105_0E Rohde & Schwarz Measurements on FM Transmitters for Acceptance, Commissioning and Maintenance 2
5 Measurements ...................................................................... 27
5.1 Transmitter Output Level ...........................................................................27
5.2 Frequency Accuracy ..................................................................................30
5.3 Frequency Deviation Constant: Checking the Transmitter's Frequency
Modulator Constant ...................................................................................32
5.4 Frequency Response .................................................................................37
5.4.1 Amplitude-Frequency Response ..................................................................37
5.4.2 Phase Response ..........................................................................................43
5.4.3 Balance .........................................................................................................48
5.5 Stereo Crosstalk .........................................................................................51
5.6 Nonlinear Distortion ...................................................................................54
5.6.1 Total Harmonic Distortion (THD) ..................................................................54
5.6.2 Dual Frequency Distortion (DFD) .................................................................58
5.7 Spurious modulation (Signal-to-Noise Ratio, S/N) .................................65
5.7.1 Spurious Frequency Modulation...................................................................65
5.7.2 Spurious Amplitude Modulation ....................................................................70
5.7.3 Noise Power Density at 57 kHz ....................................................................73
5.8 Polarity of the Input ....................................................................................76
5.9 Digital Input Signal (AES/EBU) .................................................................79
6 Abbreviations ....................................................................... 81
7 Auxiliary Information ........................................................... 81
8 Ordering Information ........................................................... 82
A Input Level and Frequency Deviation ................................. 83

A.1 Overview in Tables .....................................................................................83
A.2 Mathematical Correlation Between the Input Level and the Frequency
Response ....................................................................................................84
A.3 Example for Calculating the Required Audio Level ................................85
B Automated Measurements with R&S®TxCheck ................. 86
Overview
1 Overview
Frequency modulation (FM) remains very popular in analog broadcasting. Compared
with amplitude modulation (AM), FM needs more bandwidth, but it is also more im-
mune to interference and offers a better signal-to-noise ratio (modulation gain). FM
also supports nonlinear (class C) amplifiers, which are more efficient.
Despite the advent of advanced digital transmission methods, analog broadcasting

remains highly important. Until now, measurements on FM transmitters in connection
with acceptance testing, commissioning and maintenance required using a variety of
T&M instruments.
®
The R&S ETL TV analyzer combines these instruments' capabilities in a single unit
and can completely replace them. Now, for the first time, acceptance test measure-
ments can be conducted on FM transmitters quickly and easily using just one compact
®
test instrument. The R&S ETL provides the functionalities of a power meter, spectrum
analyzer, audio generator, FM measurement demodulator, stereo decoder, audio
analyzer and more in just one box.
Fig. 1: R&S®ETL.
This application note covers the fundamental FM measurements performed during FM

transmitter acceptance testing, commissioning and maintenance. These measure-
ments are conducted using test signals. FM transmitter test standards are highly
country- and customer-specific, so the settings and test limits contained in this applica-
tion note are only intended as examples. The measurements described here are based
on field reports and Rohde & Schwarz transmitter test department reports, as well as
the IEC 244-13 test standard, and technical guidelines issued by the Institute for
Broadcasting Technology (IRT) for public broadcasters in Germany, Austria and Swit-
zerland.
Section 2 briefly describes the basics of FM broadcast technology. Section 3 explains

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the settings available on the R&S ETL. Section 4 begins by covering the preparations
for testing. That includes information on the necessary test equipment and setup, as
well as steps to protect the T&M equipment against destructively high input power.
®
Section 4 then goes on to describe basic configuration of the R&S ETL for conducting
measurements. Section 5 details individual types of measurements, including the
®
requisite R&S ETL configurations.
Overview
Appendix A explains the linkage between a transmitter's modulation input level and the
®
resulting frequency deviation. Appendix B shows how to use the R&S TxCheck soft-
®
ware with the R&S ETL to automate many of the measurements covered here in this
document.
FM Basics
The Multiplex (MPX) Signal
2 FM Basics
In frequency modulation (FM), the carrier frequency wave is varied in sync with the
transmitted signal. The change in the carrier frequency caused by modulation is re-
ferred to as the frequency deviation. The greater the amplitude of the information
signal, the greater the frequency deviation (see Fig. 2 and Fig. 3).
Fig. 2: Audio scope display showing a frequency-modulated 1 kHz audio signal – on the left with a
20 kHz frequency deviation (resulting from 0 dBu), and on the right with a 40 kHz frequency deviation
(resulting from 6 dBu).
Fig. 3: RF spectrum of a frequency-modulated 1 kHz audio signal – on the left with a 20 kHz frequen-
cy deviation (resulting from 0 dBu), and on the right with a 40 kHz frequency deviation (resulting
from 6 dBu).
2.1 The Multiplex (MPX) Signal

There are two types of audio signals: mono and stereo. Stereo signals are more com-
mon in broadcast radio. In a stereo transmission, the FM transmitter is used to transmit
stereophonic signals, which consist of two independent audio channels.
The FM stereo system was designed to be backward compatible and allow broadcast
signals to be received on mono equipment as well. The pilot tone multiplex system,
defined in CCIR recommendation 450, section 2, was developed for this purpose. In
this system, the modulation signal is generated by a special stereo coder. This can be
a separate, upstream device, or it can be integrated in a transmitter. A transmitter
without a stereo coder can be used as a mono transmitter.
FM Basics
The Multiplex (MPX) Signal
A matrix circuit in the stereo coder generates a sum signal M (middle) and a difference
signal S (side) from the left and right audio signals (each of which has a bandwidth of
15 kHz). The sum signal M equates to the mono signal transmitted by a mono transmit-
ter. The difference signal S is amplitude-modulated on a subcarrier at 38 kHz. This
subcarrier is suppressed to reduce the bandwidth required, and a pilot tone at 19 kHz
is transmitted instead. The pilot tone enables a receiver (decoder) to identify that the
broadcast signal is stereo; it also enables a stereo receiver to recover the suppressed
subcarrier (at 38 kHz) and demodulate the difference signal.
The stereo coder's full output signal is called a multiplex (MPX) signal. This essentially
consists of three parts:
L R
 The sum signal M   , with a bandwidth of 40 Hz to 15 kHz
 2 
 The 19 kHz pilot tone
L R 
 The modulated difference signal S   , with a bandwidth of
 2 
23 kHz to 53 kHz
As VHF radio evolved, the following ancillary signals were incorporated to support
additional services:
 Radio Data System (RDS): This carries static information (such as the sta-
tion identifier and track titles) that appears on receiver displays. The infor-
mation is transmitted digitally on a 57 kHz subcarrier
o The precursor of RDS was ARI (Autofahrer-Rundfunk-Information,
automobile radio information)
 Data Radio Channel (DARC): This is a system similar to RDS, and is used
mainly in Japan and the USA
 Subsidiary Communication Authorization (SCA): This carries an additional,
telephone-grade audio signal. The SCA ancillary signal's standard fre-
quencies are 41 kHz (for mono transmitters only), 67 kHz and 92 kHz
These ancillary signals are added to the MPX signal (see Fig. 4).
Fig. 4: Schematic diagram of an MPX signal spectrum.
FM Basics
Pre- and Deemphasis
2.1 Pre- and Deemphasis

Frequency modulation has a triangular noise spectrum. This means that the noise
power density is not constant but increases with the audio-frequency bandwidth. To
improve the signal-to-noise ratio at high frequencies, the stereo coder uses preempha-
sis. This is a process in which high frequencies are boosted prior to transmission.
Preemphasis utilizes a time constant that differs from country to country: In Europe and
Japan, it is generally 50 µs; in the USA, 75 µs. To return to a linear frequency re-
sponse, the preemphasis must be reversed by the receiver in a process called deem-
phasis.
2.2 RF Bandwidth
The signal generated in the stereo coder is frequency-modulated in an exciter. Based
on Carson's rule, the following applies approximately to the bandwidth of a frequency-
modulated signal (see Fig. 5):
98 % of the spectral power within
99 % of the spectral power within

where f Carrier  frequency deviation
Fig. 5: RF spectrum of a frequency-modulated 1 kHz audio signal (left) and a frequency-modulated

15 kHz audio signal (right). Both signals have a frequency deviation of 40 kHz.
2.3 Stereo Decoder

In the decoder, the left channel (L) consists of the sum signal plus the difference sig-
nal; the right channel (R) consists of the difference of the sum signal and the difference
signal:
L R L-R
M+S=  =L
2 2
L R L-R
M-S=  =R
2 2
FM Basics
Transmitter Inputs
2.4 Transmitter Inputs

Transmitters have an MPX input into which the MPX signal is fed. Transmitters with an
integrated stereo coder have L and R inputs in addition to the MPX input.
Audio Engineering SocietyEuropean Broadcasting Union Most of today's advanced

transmitters have an Audio Engineering Society/European Broadcasting Union
(AES/EBU) input that accepts both stereo and mono digital audio signals. This input is
specified in the AES3 standard. AES/EBU supports impedances of 110 ohms (on
AES3 balanced cables) and 75 ohms (on unbalanced coaxial cable). The signal level
for AES/EBU is given in decibels relative to full scale (dBFS) and is relative to the
highest possible audio level.
R&S®ETL Settings for FM Measurements
3 R&S®ETL Settings for FM Measurements

®
The R&S ETL combines several FM signal analyzers (see Fig. 6) with a stereo coder
and an audio test signal generator in a single instrument. This means it offers a wide
variety of possible settings. For the most part, though, only a few settings need to be
made for any given measurement. This application note details the settings required
for each type of measurement (see Section 5).
Fig. 6: Simplified overview of the analysis functions for acceptance-testing an FM transmitter.
This section provides an overview of the available settings, what they do, and how they
interact. Having this background knowledge is not a prerequisite for performing the
measurement, because information on all of the required settings is provided along
with the measurement descriptions in Section 5. Here, in Section 3, users can read
about what the settings actually mean.
®
The R&S ETL provides the following configuration dialogs for FM measurements:
● Radio settings (3.1)
● Audio generator (3.2)
● Configuration dialogs for individual measurements:
 Audio analysis measurements (3.3):
 Frequency response
 Crosstalk
 Level
 Signal-to-noise (S/N) ratio
 Total harmonic distortion (THD)
 Dual frequency distortion (DFD)
 Modulation analysis measurements (3.4):
 Audio scope
 Audio spectrum
 MPX power and peak deviation
 MPX deviation distribution
 Multipath detection
 RDS
General FM Settings – Radio Settings
In configuration dialogs, it is important always to configure the settings from the top
down, because some of the settings available are contingent upon others. For in-
stance, the "Stereo Decoder" setting under "Radio Settings" is only available if "FM
Stereo" has been selected under "Radio Standard".
3.1 General FM Settings – Radio Settings

®
The basic FM settings are available when the R&S ETL is set to "Radio" mode under
"TV/Radio Analyzer/Receiver" (MODE→TV/Radio Analyzer/ Receiver→Radio), and
they can be configured under "Radio Settings" (see Fig. 7 ).
Fig. 7: Switching the R&S®ETL to "Radio" mode and opening the "Radio Settings" dialog.
The settings in the "Radio Settings" configuration dialog comprise the following five
groups; these are described in the sections indicated below in parentheses (see
Fig. 8).
Modulation Standard (3.1.1)
Stereo Decoder (3.1.2)
Outputs (3.1.3)
Universal Interface (Option B201) (3.1.4)
DUT Parameters (3.1.5)
Fig. 8: The "Radio Settings" configuration dialog, accessed via MEAS→Radio Settings.
3.1.1 Modulation Standard
Radio Standard
The radio standard must be selected to match the transmitter's operating mode:
 FM Mono: This should be selected for mono-only transmitters because, ac-
cording to some specifications (such as RaiWay) they may require an audio-
frequency bandwidth of up to 17.5 kHz. In stereo, this bandwidth is technically
unfeasible. Choosing "FM Mono" means that no stereo measurements will be
®
available for selection in the R&S ETL menu.
"FM Stereo" should be selected as the radio standard for measurements on
stereo transmitters in mono mode when an audio-frequency bandwidth of
15 kHz is sufficient, or for measurements on the sum signal M.
 FM Stereo: This setting causes the R&S ETL to behave like a receiver with a
®
stereo measurement decoder. The audio-frequency bandwidth is limited to

15 kHz.
Channel Bandwidth
A narrow channel selection (lower bandwidth) clips the sidebands. As bandwidths
narrow, distortion increases. For this reason, to take precise measurements on trans-
mitters, users should select the largest available bandwidth (1 MHz). However, when
conducting measurements on a receive antenna with adjacent channels, it may be
necessary to select narrower bandwidths in order to limit interference from adjacent
channels as much as possible.
Data System
The "Data System" setting enables measurements to be performed on RDS signals
(including the RBDS variant used in the USA) and on DARC signals. Choosing "None"
under "Data System" means that these measurements will not be available or per-
formed.
The only measurement available for DARC is frequency deviation ("DARC Deviation").
®
The R&S ETL has a decoder for RDS and RBDS (MEAS→Modulation Analy-
sis→RDS→Extended RDS Analysis). "RBDS mode" must be enabled for RBDS (see
®
Fig. 9, top right). The "extended RDS analysis” option in the R&S ETL makes it possi-
ble, among other things, to analyze transmitter names and alternative frequencies.
Fig. 9: RDS/RBDS decoder.
SCA Mode
The "SCA Mode" setting allows the SCA ancillary signal to be demodulated and meas-
ured. The setting distinguishes between "Narrow" (approx. 14 kHz bandwidth of the
modulated subcarrier, which is used in the USA, for instance) and "Wide" (approx.
26 kHz bandwidth of the modulated subcarrier, which is used, in Italy, for example). If
this is set to "Off", these measurements are not available or performed. If SCA is
activated, the center frequency of the subcarrier to be demodulated must be entered
under "SC Freq" (SC = subcarrier); this frequency defaults to 41 kHz (mono transmit-
ters only) or 67 kHz. For stereo transmitters, 92 kHz is also common.
3.1.2 Stereo Decoder
Pilot Dev Threshold

"Pilot Dev Threshold" sets how high the minimum frequency deviation caused by the
pilot signal must be in order for the signal to be recognized as stereo. This affects the
appearance of the status bar on the lower right of the measurement screen: If the pilot
®
deviation is smaller, the R&S ETL displays the red warning "MONO". This setting also
affects the automatic switching of the 1/L and 2/R output signals from stereo to mono
(see 3.1.3).
The stereo decoder's actual synchronization with the pilot signal does not depend on
this setting.
3.1.3 Outputs
Selected signals can be fed in analog or, in some instances, in digital form to an exter-
nal audio analyzer for extended analysis. Two outputs are available for this purpose
(see Fig. 10):
®
● CCVS (color composite video signal; the R&S ETL also uses this to output analog
TV signals – thus the name)
● Balanced outputs (1/L and 2/R)
Fig. 10: The R&S®ETL has two outputs for more extensive audio analysis.
The demodulated digital signal in AES/EBU format (available on the CCVS output) has
better signal quality than the demodulated analog signals on the 1/L and 2/R outputs.
This is why, if possible, the AES/EBU format should be used when an external audio
analyzer is connected.
1/L, 2/R Output

Outputs 1/L and 2/R can be used for two purposes. First, outputs 1/L and 2/R can
supply a generator signal to feed a transmitter. Second, a signal (a mono, decoded
stereo, M&S or SCA signal) received on the RF input can be output for more detailed
audio analysis (e.g. on an external audio analyzer). If "Auto" is selected under "1/L, 2/R
Output", a mono or stereo signal is output, depending on the pilot signal threshold
setting (see 3.1.2).
The selected signal also appears on the headphone output (AF Out) and in the
AES/EBU signal; the latter can be selected on the CCVS output if required.
It is important to note that the 1/L and 2/R outputs are balanced but not floating. This
means that it is not possible to produce an unbalanced signal by connecting an output
to ground.
Deemphasis
The "Deemphasis" setting under "Outputs" affects the headphone output (AF Out), the
1/L and 2/R outputs and the AES signal. The deemphasis settings available for "Auto",
"Mono", "Stereo" and "M&S" under "1/L, 2/R Output" are 50 µs, 75 µs or off. The
deemphasis settings available for SCA under "1/L, 2/R Output" are 100 µs, 150 µs or
off.
Deviation for 6 dBu output level

For technical reasons, the output levels on 1/L and 2/R are limited to 12 dBu. By
changing the "Deviation for 6 dBu output level" setting, it is possible to adjust the
output level range to suit specific requirements. If this is set to 40 kHz, signals with a
frequency deviation of up to 80 kHz can be output without clipping. If set to 75 kHz,
signals with a maximum deviation of 150 kHz can be output without clipping.
Note that the maximum possible signal-to-noise ratio on this output drops as the fre-
quency deviation increases.
CCVS Output
The MPX signal, the demodulated signal in digital AES/EBU format, the pilot signal or
the RDS/DARC or SCA subcarrier can be output on the CCVS output.
The demodulated signal in the digital AES/EBU format contains the signal selected
under "1/L, 2/R Output" (mono, stereo, or M&S).
3.1.4 Universal Interface (Option B201)
Connector Config
The "Connector Config" setting allows the way the audio generator's signal outputs are
assigned to be adjusted to the transmitter's signal inputs. This helps to avoid having to
disconnect and reconnect cables.
There are two choices available for output signal assignment:

● "L/MPX/AF – R – AES"
This is used if the transmitter under test has a combined input for L and MPX.
● "L – R – MPX/AF/AES"
This can be selected if the transmitter has separate L, R and MPX inputs. Recon-
nection will be necessary in order to measure the AES/EBU modulation input.
If the way the signal outputs are assigned does not match the transmitter's signal
inputs, reconnection will be necessary.
A third possible choice is available under "Connector Config"; this allows received and
decoded RDS data and the RDS clock to be output:
● RDS Clk – RDS Dat – none:
This setting is not required in connection with the measurements described here.
The same setting is available in the audio generator configuration dialog on the
®
R&S ETL (see 3.2.3).
3.1.5 DUT Parameters
The settings under "DUT Parameters" (DUT = device under test, in other words the FM
®
transmitter being tested) enable the R&S ETL to automatically compute the requisite
signal level for a desired frequency deviation. Depending on the transmitter input used,
the deviation and either the analog input level ("Input Level Analog") or the digital input
level ("AES/EBU") must be entered in accordance with the transmitter settings.
Audio Generator Settings
3.2 Audio Generator Settings

®
The requisite audio generator settings are available if the R&S ETL is set to "Radio"
mode under "TV/Radio Analyzer/Receiver" (MODE→TV/Radio Analyzer/ Receiv-
er→Radio). The audio generator settings can be configured under Audio Genera-
tor→Audio Generator Setup (see Fig. 11 and Fig. 12).
Fig. 11: Switching to "Radio" mode on the R&S®ETL and initiating the "Audio Generator Setup"
configuration dialog.
Fig. 12: The "Audio Generator Setup" configuration dialog. This is accessed via MEAS→Audio
Generator→Audio Generator Setup.
The generator settings for audio analysis measurements can also be configured in the
configuration dialog ("Setup") for each type of measurement (see 3.3). The settings are
easier to make there because the configuration dialog only offers relevant and appro-
priate settings, which is why using this dialog is recommended. In the THD setup, for
instance, no waveform setting is available because the measurement is only carried
out with a single tone. If the audio generator is to be used for purposes other than
audio analysis measurements, the settings must be made in "Audio Generator Setup".
3.2.1 Type
The audio generator's "Type" setting determines the type of signal to be generated.
®
The signal to be generated is available either on the R&S ETL-B201 hardware option
or on the 1/L and 2/R outputs (see Fig. 13), depending on the signal type.
Fig. 13: Rear view of the R&S®ETL with the R&S®ETL-B201 hardware option and the 1/L, 2/R ports.
The following settings are available under "Type":

● Analog (Option B201):
An uncoded analog stereo signal (L, R) to feed into an operational stereo
coder, or a general audio signal (AF, audio frequency) up to 100 kHz to feed
directly into the transmitter MPX input, bypassing the stereo coder.
● MPX (Option 201):

Analog MPX signal (M+S, pilot and, possibly, ancillary signals) to feed into
the transmitter's MPX input.
● AES/EBU (Option B201):

Uncoded digital stereo signal (e.g. to feed into a digital operational stereo
coder).
● Analog (1/L, 2/R):

Uncoded analog stereo signal that uses the 1/L and 2/R ports. Unlike the
"Analog (Option B201)" type, the output signal is balanced; L=-R and L<>R
signals are available, too (see 3.2.2). However, the signal-to-noise ratio and
bandwidth (15 kHz) are lower and the frequency response greater. The "Ana-
log (Option B201)" type should therefore be used if possible.
3.2.2 Signal
The composition of the signal generated can be selected here. The following signals
are available:
● AF (= audio frequency): general audio signal up to 100 kHz
● L: left only, right off
● R: right only, left off
● L=R: left and right with same phase
● L=-R: left and right with opposed phase
● L<>R: left and right with different frequencies; the frequency and level can be
selected separately
The options available depend on the setting under "Type" (see 3.2.1):
● Analog (Option B201): AF, L, R, L=R
● MPX (Option B201): L, R, L=R, L<>R, L=-R, SCA
● AES/EBU (Option B201): L, R, L=R, L=-R, L<>R
● Analog (1/L,2/R): L, R, L=R, L=-R, L<>R
3.2.3 Connector Config

®
As already noted in 3.1.4, this setting makes it possible to adapt the R&S ETL-B201
hardware option's audio generator outputs to the transmitter's modulation inputs, and
this setting can also be changed in the Radio Setting menu.
The graphic display in "Audio Generator Setup" (see Fig. 14) shows the signals cur-
®
rently configured on the R&S ETL-B201 hardware option's output or on the 1/L and
2/R outputs. Green means that the signal is output; red means that no signal is output.
Fig. 14: Screenshots showing two possible signal configurations for the audio generator (bottom)
and how they map to the generator outputs on the R&S®ETL (top).
3.2.4 Waveform
Depending on the type of measurement, a single-tone or dual-tone signal needs to be

generated. The following settings are available:
● "Single Tone":
A single sine-wave tone is generated at a chosen frequency for each channel. This
is needed, for instance, for measuring frequency response (5.4) or total harmonic
distortion (5.6.1).
● "Dual Tone, constant spacing" or "Dual Tone independent frequencies":
Two sine-wave signals are generated on each channel. Both tones have the same
®
amplitude. Due to the different requirements, the R&S ETL offers two convenient
input options to suit different test specifications:
– Dual Tone, constant spacing: The frequency of the higher tone and the fre-
quency spacing are specified – to measure the dual-frequency distortion, for
example (5.6.2.1)
– Dual Tone independent frequencies: Two independent frequencies are speci-
fied – to test input polarity, for example (5.8)
3.2.5 Ampl Definition and Level
The dimension (unit) for the generator amplitude is selected under "Ampl Definition":
● Level:
The level in dBu (0 dBu = 600 Ω • 1 mW ≈ 0,7746 V ).
● Peak Voltage:
The peak voltage in V. The peak-to-peak voltage cannot be entered as such, but it
can be specified easily here by applying a conversion factor of 2.
With a dual-tone signal, the selected peak voltage is the total of the amplitude of
both tones.
The reason for entering the peak value here rather than the RMS value (more
common in audio analysis) is that with FM the frequency deviation resulting from
the generator signal is usually specified as the peak deviation.
● Desired DUT Deviation:
The desired transmitter frequency deviation in kHz resulting from the generator
level is entered directly here. This convenient function computes and inserts the
requisite level based on the "DUT Parameters" entered under "Radio Settings"
(see 3.1.5). For instance, if a THD measurement is conducted with a deviation of
100 kHz, entering the "Desired DUT Deviation" here saves having to calculate the
requisite generator level (see appendix A).
If preemphasis is enabled on the modulator, "Preemphasis Comp" (see 3.2.6) can
compensate by reducing the level generated by the audio generator.
3.2.6 Preemphasis/Preemphasis Compensation
Preemphasis
The preemphasis function is only available for the generator type "MPX (Option
B201)". It is part of the MPX generator contained in the stereo measurement decoder.
Preemphasis compensation
If "Ampl Definition" = "Desired DUT Deviation" has been selected, the "Preemphasis
Compensation" setting is available for all other generator types ("Analog (Option
B201)", "AES/EBU (Option B201)" and "Analog (1/L, 2/R)").
In accordance with the chosen time constant, the audio generator's level is reduced
automatically in line with the frequency to provide a constant frequency deviation when
transmitter preemphasis is activated. This makes measurements that require a con-
stant frequency deviation (e.g. THD or crosstalk) easier to conduct.
Configuration Dialogs for Audio Analysis Measurements
3.3 Configuration Dialogs for Audio Analysis Measure-

ments
The following audio analysis measurements are available:
 Frequency response
 Crosstalk
 Level
 Signal-to-noise (S/N) ratio
 Total harmonic distortion (THD)
 Dual frequency distortion (DFD)
The audio analysis measurements' configuration dialogs can be called up in the rele-
vant measurement mode, and they are organized into three groups (see Fig. 15).
Demodulator (3.3.1)
Audio generator (3.3.2)
Measurement options (3.3.3)
Fig. 15: "TV/Radio Analyzer/Receiver" operating mode, MEAS→Audio Analysis→Frequency Re-

sponse→Frequency Response Setup.
The configurations available depend on the given measurement type and are ex-
plained here using an example based on a frequency response measurement.
3.3.1 Demodulator
The signal to be analyzed is selected under "Signal Path". In audio analyzer measure-
ments, the choices available are limited to the signals that the generator can generate.
A deemphasis setting of 50 µs, 75 µs or off can be selected for stereo-decoded signals
(L, R, L&R, M&S, M, S).
Configuration Dialogs for Modulation Analysis Measurements
3.3.2 Audio Generator
The choice of generator settings under "Audio Generator" is confined to generator

settings relevant for the selected type of measurement (see 3.2). With measurements
that call for automatic switching between the L path and the R path (in Amplitudenfre-
quenzgang, 5.4.1, for instance), the colored indicator is half green and half red (see
Fig. 15). The outputs are switched automatically in automated measurements.
®
To avoid unnecessary wear on the relays in the R&S ETL-B201 option, measurements
are only carried out once in each position. (A measurement can be restarted with the
RUN hardkey if required.) If the generator signal needs to alternate (e.g. for long-term
measurements), "Alternate L and R continuously" can be enabled.
3.3.3 Measurement Options
The configurations available under "Measurement Options" depend on the given

measurement type and are explained in context in this application note (see Section 5).
3.4 Configuration Dialogs for Modulation Analysis

Measurements
The following measurements are available under "Modulation Analysis". They are
mainly intended to be conducted during operation:
 Audio scope
 Audio spectrum
 MPX power and peak deviation
 MPX deviation distribution
 Multipath detection
 RDS
The settings in the modulation analysis measurements' configuration dialogs can be

called up during the relevant measurements. The configurations available depend
largely on the given measurement type.
This application note does not cover measurements conducted during operation, so
the individual configuration options are not explained here.
Preparatory Steps
Required Equipment
4 Preparatory Steps
4.1 Required Equipment

Basic configuration
®
R&S ETL TV analyzer with:
● options as needed (see Section 8)
● current firmware (available free of charge at
www.rohde-schwarz.com/product/ETL.html)
Application- or measurement-specific configurations
Transmitter operation without signal broadcasting for transmitter ac-

ceptance testing or commissioning
Dummy antenna
For measuring transmitter output level with a measurement uncertainty of

< 0.1 dB
®
Additional power sensor, e.g. R&S NRP-Z91
If the directional coupler is not part of the transmitter

Directional coupler
Preparatory Steps
Test Setup
4.2 Test Setup
Fig. 16: Test setup.
®
The EXT REF reference input located at the rear of the R&S ETL TV analyzer is used
to connect the instrument to the 10 MHz GPS time reference available at the transmit-
®
ter station. The optional power sensor can be connected to the R&S ETL via USB or
® ®
via the sensor input on the R&S ETL hardware option R&S FSL-B5.
®
The RF input on the R&S ETL (IN1) or the optional power sensor (IN2) is connected to
the measurement interface of the transmitter output (M1 = forward, M2 = reflected).
For transmitter acceptance tests, the audio generator outputs located at the rear of the
®
R&S ETL are connected to the transmitter inputs (marked green, see 3.1.4).
The transmitter output is connected to a dummy antenna before the broadcast signal is
applied to the antenna diplexer. As a result, the test port at the antenna diplexer (M3)
is available as an additional measurement point.
Preparatory Steps
Protection Against Destructive Input Power
4.3 Protection Against Destructive Input Power

®
The R&S ETL allows maximum input power peaks of 36 dBm (short-term, < 3 s), while
®
the recommended, separate R&S NRP-Z91 power sensor can handle up to 23 dBm.
It is, therefore, recommended that additional attenuators be used as needed to limit the
average total power at the individual test ports to a range from 0 dBm to 10 dBm. This
range provides adequate protection against short-term power peaks, while having a
negligible effect on the instrument accuracy. The resulting attenuation must of course
be taken into consideration during specific measurements, such as the transmitter
output level.
4.4 R&S®ETL Default Configuration for Measurements

The following conventions are used in these procedures:
● Terms in capital letters refer to key labels, e.g. "FREQ" for
● Bulleted lists (e.g. ● Radio Standard) identify settings made in the currently dis-
played configuration dialog box
● All other terms refer to the softkeys that are currently displayed along the right-
hand side of the screen. Arrows (→) separate the keys to be pressed in sequence.
Preparatory Steps
R&S®ETL Default Configuration for Measurements
General settings
1
SETUP→Reference Ext: Use the external 10 MHz reference frequency
MODE→TV/Radio Analyzer/Receiver→Radio
MEAS→Radio Settings
Modulation Standard
 Radio Standard: FM Stereo
 Select Channel Bandwidth: 400 kHz
 Data System: None
 SCA Mode: Off
Stereo Decoder
 Pilot Dev Threshold: 500 Hz
Outputs: Setting only required if the outputs 1/L and 2/R or CCVS are used for ex-
tended signal analysis (see 3.1.3)
Universal Interface (Option B201): To be configured to match transmitter (see

3.1.4)
DUT Parameters: To be configured to match the transmitter (see 3.1.5)

FREQ→Channel RF: Select based on the transmit frequency
Level adjustment
2
MENU→Adjust Attenuation
AMPT→Preamp: Off
AMPT→More→Preselector: Off
3
AMPT→RF Atten Manual: Select the lowest possible setting without overloading
1
Only necessary if the frequency accuracy is to be measured with very high precision
-5
(> 10 )
2
For rough level adjustment.
3
Overload warnings appear centered at the top of the display as "IFovl" or "Ovld".
Measurements
Transmitter Output Level
5 Measurements
This section explains the measurements that are performed on the analog transmitter
input. After that, Section 5.9 covers the differences associated with using the digital
transmitter input (AES/EBU input).
5.1 Transmitter Output Level

When measuring the transmitter output level, it is important to ensure that the dis-
played power level refers exclusively to the power that has been decoupled by the
®
directional coupler. The coupling attenuation can be entered using the R&S ETL's "Ref
Level Offset" function, which is then automatically calculated into the displayed value.
®
From the "Overview" mode, you can have the R&S ETL measure the signal level
directly via the RF input, at an accuracy of 1 dB. Using a separate power sensor
makes it possible to achieve an accuracy of 0.1 dB.
When using the "Overview" menu, it is possible to select the unit of measurement and
set the predefined limits from the table via MEAS→Overview→Edit Table (see Fig. 17).
Measured values that are not within the set limits are displayed in red. To ensure that it
is possible to quickly recognize values that are outside the limits – even on black-and-
white printouts – such values are also marked with an asterisk (*).
Fig. 17: "TV/Radio Analyzer/Receiver" mode in the MEAS→Overview→Edit Table menu: Selecting the
unit of measurement for the level results.
Measurements
This section describes how the transmitter output level is measured for a signal that is
modulated with a maximum operating deviation (for example, 75 kHz). For the dimen-
sion (unit of measurement), the configuration proposed here employs "Desired DUT
Deviation" for the generator amplitude (for the "Ampl Definition" setting). As an alterna-
tive, it is also possible to use the "Level" or the "Peak Voltage".
Procedure: Transmitter output level

Check to ensure that the max. input power is not exceeded (see Section 4.3).
In each case, perform these steps at the test port:
 M1, for forward power
 M2, for reverse power
Configure the general settings as described in Section 4.4.
Set the transmitter input to "AF Stereo".
On the transmitter, turn on the preemphasis.
MEAS→Overview→Audio Generator→Audio Generator Setup:
 Type: Analog (Option B201)
 Signal: L=R
 Connector Config: Set this parameter to match the transmitter (see 3.2.3)
 Waveform: Single Tone
 Freq: 500 Hz
 Ampl Definition: Desired DUT Deviation1
 Desired DUT Dev: For example, 75 kHz
 Preemphasis Comp: Set this parameter to match the transmitter's
preemphasis setting
Adjust the level as described in Section 4.4.
Method 1: Method 2:
"TV/Radio Analyzer/Receiver" Power sensor
AMPT→More→ExpectedLv Offset: Set AMPT→More→Ref Level Offset: Set to
to the full coupling attenuation at the test the full coupling attenuation at the test
port for immediate compensation. port for immediate compensation.
Feed a signal into the RF input on the Connect the power sensor (IN2), which is
® ®
R&S ETL (IN1) connected to the R&S ETL via USB or
sensor input, to the test port.
MODE→Spectrum Analyzer
MEAS→Overview MENU→Power Meter→Frequency Cou-
pling: Center
MENU→Power Meter→Power Meter→On
Read the level value (see Fig. 18). Read the level value (see Fig. 19).
1
For this it is necessary – as described in the section on the basic settings (Sec-
tion 4.4) – for the transmitter's target operating parameters to be set correctly under
“DUT Parameters“.
Measurements
Fig. 18: "TV/Radio Analyzer/Receiver" mode, MEAS→Overview menu: The level can be read in the
first table row, in the status bar on the test screen or in the zoomed view (MEAS→Overview→Zoom).
Fig. 19: Spectrum analyzer mode: FM spectrum with integrated reading from the power sensor
displayed at the top right.
Measurements
Frequency Accuracy
5.2 Frequency Accuracy

It is possible to measure the frequency accuracy with or without modulation. The
®
R&S ETL has been designed to also be able to measure the frequency accuracy with
modulation.
The level of precision at which the frequency accuracy can be measured depends on
how long it has been since the last time that the T&M instrument was calibrated. In
general, it is possible to assume that an external reference is required in order to
-5
measure at an accuracy > 10 (see Basic Configuration 4.4).
Procedure: Frequency accuracy

Check to ensure that the max. input power is not exceeded (see 4.3).
®
Connect the R&S ETL (IN1) to test port M1.
Method 1: Method 2:
With modulation Without modulation
Set the transmitter input to AF stereo.
Set the transmitter to MPX.
On the transmitter, turn on preemphasis.
MEAS→Overview→Audio Generator→Audio Generator Setup:
 Type: Analog (Option B201)  Signal: OFF
 Signal: L=R
 Connector Config: Set to match the (None of the other settings influence the
transmitter (see 3.2.3) results.)
 Freq: 500 Hz
 Ampl Definition: Desired DUT Devia-
tion1
 Desired DUT Dev: For example,
40 kHz
 Preemphasis Comp: Set to match
the transmitter's preemphasis setting
MEAS→Overview
Read the value for the carrier frequency offset (see Fig. 20).
1
For this it is necessary – as described in the section on the basic settings (Sec-
tion 4.4) – for the transmitter's target operating parameters to be set correctly under
“DUT Parameters“.
Measurements
Frequency Accuracy
Fig. 20: "TV/Radio Analyzer/Receiver" mode, MEAS→Overview menu: You can read the results for
frequency accuracy ("Carrier Frequency Offset") in the second table row, in the status bar on the test
screen or in the zoomed view (MEAS→Overview→Zoom).
Measurements
Frequency Deviation Constant: Checking the Transmitter's Frequency Modulator Constant
5.3 Frequency Deviation Constant: Checking the

Transmitter's Frequency Modulator Constant
When the transmitter's frequency modulator constant is set correctly, the correspond-
ing nominal deviation (of the frequency) arises at a nominal level (usually 6 dBu). In the
TR 5/3.5 guideline, the nominal deviation is also referred to as the standard testing
deviation. In this measurement, the nominal deviation is the measurement variable to
be tested.
Depending on the specific country and on the applicable specifications, the input level
is expressed in dBu or in volts. As a "pseudo" unit of measurement, dBu is a logarith-
mic measure of voltage (√ ). The nominal deviation also
varies depending on the country and on the applicable specifications. Germany, for
instance, uses 40 kHz at 6 dBu, and Switzerland uses 50 kHz at 6 dBu for this. To-
gether, the input level and the frequency deviation yield the modulator constant.
To enable you to make a quick check, the frequency deviation of the L, R, M, S and
MPX signals are shown in the overview (see Fig. 20, lines 4 to 8). The values indicated
there are measured using a peak detector.
For precise verification, it is possible to perform a measurement in the level mode

(MEAS→Audio Analysis→Level). In that case, there are four detectors, each featuring
different characteristics, available for measuring the frequency deviation:
● Selective: An FFT-based detector that selectively measures the largest spectral
lines arising in the AF spectrum. Harmonics are not included in the measurement
and, due to the narrowband characteristics, noise has very little influence on the
measurement results. In addition, the system displays the frequency of the meas-
ured signal.
● PK: Peak detector. Used to measure the peak deviation of composite signals.
Since the peak value is determined in an absolute measurement, noise has a rela-
tively large influence on the measurement results. Consequently, the measured
value tends to be somewhat too high. This detector is also used for the frequency
®
deviation display in the R&S ETL overview menu.
● QPK: Quasi-Peak Detector. As specified by ITU-R BS.468-4, this detector shows
the RMS value for a sinusoidal signal, but not for other types of signals. It reacts to
specific pulses and pulse groups in a predefined manner. Consequently, it is de-
signed to deliver the best possible T&M representation of the effect that interfer-
ence has on the human ear. In order to be able to indicate values from the various
detectors in the same order of magnitude, the measured value is multiplied by the
factor √ . The display shows 𝑄𝑃𝐾 √ .
● RMS: Root mean square detector. Shows the average value independently of the
shape of the curve. Noise has relatively little influence on the results, although this
influence is significantly stronger than it is with the selective detector. As with the
QPK value, this value is multiplied with the factor √ . The display shows 𝑅𝑀𝑆 √ .
The measured values for the various detectors are displayed simultaneously (see
Fig. 24 and Fig. 25).
Measurements
®
For displaying the measured frequency deviation, the R&S ETL offers four possibili-
ties, which can be selected in the "Audio Level Setup" under "Mode" (see Fig. 21):
● Absolute: Absolute frequency deviation measured in Hz (for example, 40.525 kHz)
● Relative (dB): Variance of the frequency deviation in dB relative to the reference

deviation entered under "Ref Deviation" (for example, 0.114 dB)
Deviation
Relative deviation dB log
Reference Deviation
● Relative (%): Frequency deviation expressed as a percentage of the value entered

under "Ref Deviation" (for example, 101.317 %)
Deviation
Relative deviation
Reference Deviation
● Relative Δ(%): Difference between the frequency deviation and the value entered
under "Ref Deviation" (reference deviation) expressed as a percentage (for exam-
ple, 1.317 %)
Deviation – Reference Deviation
Relative deviation
Reference Deviation
Fig. 21: Configuration dialog for "Audio Level Setup," which can be called up via MEAS→Audio
Analysis→Level→Level Setup.
Measurements
This section describes the settings for testing the modulator constant without or with
the operating stereo encoder:
● Case 1: Without the operating stereo encoder

Feeding of an audio signal (AF) into the transmitter's MPX input and analysis of the
demodulated MPX signal (see Fig. 22). This verifies the transmitter's modulator
constant.
Fig. 22: Measurement configuration for verifying the transmitter's modulator constant.
● Case 2: With the operating stereo encoder

Feeding of the L and R signals into the transmitter's operating stereo encoder and
analysis of the decoded L and R signals (see Fig. 23). In addition, this makes it
possible to check to see if the modulator constant is also correct for the operating
stereo encoder being used, in other words, to ensure that the stereo encoder's
gain is one.
Fig. 23: Measurement configuration for verifying the transmitter's modulator constant when us-
ing the operating stereo encoder.
Measurements
For the dimension (unit of measurement) of the generator amplitude ("Ampl Definition"
setting), the configuration proposed here uses the "Desired DUT Deviation". As an
alternative, it is possible to use the "Level" or the "Peak Voltage".
Procedure: Verifying the transmitter's modulator constant

Test to ensure that the max. input power is not exceeded (see Section 4.3).
®
Case 1: Case 2:
Without the stereo encoder With the operating stereo encoder
Set the transmitter input to "MPX". On the transmitter, turn off the
preemphasis.
MEAS→Audio Analysis→Level→Level Setup:
Demodulator:
 Signal Path: MPX  Signal Path: L&R
 Deemphasis: Off
Audio Generator:
 Type: Analog (Option B201)  Type: Analog (Option B201)
 Signal: AF  Signal: L=R
 Connector Config: Set this value to match the transmitter (see 3.2.3)
 Freq: 500 Hz
 Ampl Definition: Desired DUT Deviation
1

 Preemphasis Comp: Off
Measurement Options:
 Mode: Select the desired display mode (such as "Absolute", for instance).
Read the "MPX Selective" values (see Read the "L Selective" and "R Selective"
Fig. 24). Use PRINT to generate a values (see Fig. 25). Use PRINT to
printout as needed. generate a printout as needed.
1
For this it is necessary – as described in the section on the basic settings (Section
4.4) – for the transmitter's target operating parameters to be set correctly under “DUT
Parameters“.
Measurements
Fig. 24: "TV/Radio Analyzer/Receiver" mode, Audio Analysis→Level menu: Variance of the frequency
deviation for the MPX signal compared to the entered standard test deviation, in percent: Level
1
Setup: Relative Δ(%).
Fig. 25: "TV/Radio Analyzer/Receiver" mode, MEAS→Audio Analysis→Level: Frequency deviation for
the L&R signal: Level Setup: Absolute.
1
There is no need to take action in response to the red "MONO" warning in the status
bar, because that warning only indicates that no pilot has been found.
Measurements
Frequency Response - Amplitude-Frequency Response
5.4 Frequency Response

®
With the R&S ETL, it is possible to measure the amplitude-frequency response and
the phase response up to 100 kHz as well as the balance (i.e., the difference between
the amplitude-frequency responses in the right and left channels).
5.4.1 Amplitude-Frequency Response
The amplitude-frequency response is measured to ensure that the output signal re-
®
mains constant across the frequency range being used. With the R&S ETL, you can
measure the amplitude-frequency response using two different detectors (RMS and
Selective). The selective detector also makes it possible to simultaneously measure
the phase and, due to its narrower bandwidth, it offers advantages for the dynamic
range; nevertheless, it requires a slightly longer measurement period.
5.4.1.1 Audio Frequency Characteristic (up to 15 kHz, or 17.5 kHz for Mono Transmit-
ters)
®
With the R&S ETL, the preemphasis can be subtracted directly from the representation
of the audio frequency response, or the preemphasis can be included in the represen-
tation. If the preemphasis is included in the representation, you can employ markers at
certain reference values to check the audio frequency response (see Fig. 26), for
example at a time constant of 50 µs at 15 kHz, an amplitude change of 13.66 dB (see
®
appendix A.2 for calculation). The R&S ETL can directly subtract the preemphasis and
plot the variance from the ideal characteristic curve, and it can display the maximum
positive and negative variance in a table (see Fig. 28). This makes it easier to read the
results and ensures that the entire amplitude characteristic is checked, and not just
individual reference points.
Fig. 26: "TV/Radio Analyzer/Receiver" mode, MEAS→Audio Analysis→Frequency Response: Typical

amplitude characteristic for an FM signal with the transmitter's preemphasis turned on and without
deemphasis on the receiver (measured as described below for Method 1 with "Deemphasis" set to
"OFF").
Measurements
The audio amplitude-frequency response up to 15 kHz can be measured separately

®
one after the other for input signal L and input signal R. Alternatively, the R&S ETL can
switch automatically between the channels. For this, "L&R" is selected under "Signal
Path". The results are displayed in a diagram with two traces.
IEC 244-13 specifies that the exciter's preemphasis is to be turned on and that the
input level is to maintained at a constant level during the measurement. The input level
is to be selected so that the frequency deviation up to 15 kHz does not exceed the
peak deviation.
In conjunction with a transmitter that has a nominal deviation of 40 kHz at an input

level of 6 dBu, in order not to exceed a peak deviation of 75 kHz, it is possible to
calculate a maximum audio input level of: log ( ) . When preempha-
sis with a time constant of 50 µs is turned on, this value must be reduced by:
log for the audio frequency 15 kHz. That results in a
√
max. audio input level of –2.1 dBu.
For the max. audio input level for other transmitter configurations and peak deviations,
and for the corresponding calculation, refer to Appendix A.
Besides the measurement with a constant level, the following configuration table also
contains the settings for a measurement with a constant frequency deviation. In the
following section, 500 Hz is used as the reference frequency. In practice, 40 Hz is also
used frequently for this.
Measurements
Procedure: Audio frequency characteristic

Check to ensure that the max. input power is not exceeded (see Section 4.3)
®
Method 1: Method 2:
With a constant level With a constant frequency deviation
(in line with IEC 244-13)
MEAS→Audio Analysis→Frequency Response→Frequency Response Setup (see
Fig. 27)
Demodulator:
 Signal Path: L&R
 Deemphasis: Set to match the trans-  Deemphasis: Off
mitter's preemphasis setting
Audio Generator:
 Connector Config: Set to match the transmitter's configuration (see 3.2.3)
 Output: Alternate L and R continuously: deactivate (see 3.3.2)
 Ampl Definition: Level  Ampl Definition: Desired DUT Devia-
1
 Level: For example, –2.1 dBu (see tion
Appendix A)  Desired DUT Dev: For example,
75 kHz
 Preemphasis Comp: Set to match the
transmitter's preemphasis setting
 Response Type: Amplitude (selective)
 Ref Freq: For example, 500 Hz
 Sweep: Linear

2
Sweep Points: 100
 Start Freq: 40 Hz
 Stop Freq: 15 kHz
Start the measurement by selecting RUN.
Set MEAS→Audio Analysis→Frequency Response→Diagram Range→Freq Re-
sponse Range so that the entire frequency response is clearly visible.
Read the variance for the audio frequency response in the table of results, (see
Fig. 28). Use PRINT to generate a printout of the measurement screen as needed.
1
Parameters“.
2
Increasing the number of sweep points results in a higher resolution but requires a
longer measurement period.
Measurements
Fig. 27: "TV/Radio Analyzer/Receiver" mode, MEAS→Audio Analysis→Frequency Re-

sponse→Frequency Response Setup: Configuration for measurement of the audio amplitude-
frequency response in line with Method 1.
Fig. 28: "TV/Radio Analyzer/Receiver" mode, MEAS→Audio Analysis→Frequency Response: Meas-

ured audio frequency response in line with Method 2; maximum positive / negative variance from the
ideal amplitude-frequency response in the table.
Measurements
5.4.1.2 Baseband Frequency Characteristic (up to 100 kHz).
The baseband frequency characteristic, which is also referred to as the MPX ampli-
tude-frequency response, is measured up to 100 kHz. IEC 244-13 specifies that the
exciter's preemphasis is to be turned off and that the input level is to maintained at a
constant level during the measurement.
®
The R&S ETL enables you to either enter the constant audio level (“Ampl Definition“ =
“Level“) or enter the corresponding frequency deviation (”Ampl Definition“ = ”Desired
DUT Deviation“).
Procedure: Baseband frequency characteristic

®
Set the transmitter input to MPX.
MEAS→Audio Analysis→Frequency Response→Frequency Response Setup
(see Fig.29):
Demodulator:
 Signal Path: MPX
Audio Generator:
 Connector Config: Configure to match the transmitter (see 3.2.3)
1
 Level: For example, 6 dBu tion
40 kHz
 Response Type: Amplitude (selective)
 Ref Freq: 500 Hz
 Sweep: Linear

2
Sweep Points 100
Read the values for the variances in the results for the baseband frequency response
in the table of results (see Fig. 30). Use PRINT to generate a printout of the meas-
urement screen as needed.
1
Parameters“.
2
Measurements
Fig.29: "TV/Radio Analyzer/Receiver" mode, MEAS→Audio Analysis→Frequency Re-

sponse→Frequency Response Setup: Configuration for measurement of the amplitude frequency
response up to 100 kHz.

ured frequency response with MPX input signal; maximum positive / negative variance from the ideal
1
amplitude-frequency response in the table.
1
Measurements
Frequency Response - Phase Response
5.4.2 Phase Response

®
Besides measuring the amplitude-frequency response, the R&S ETL makes it possible
to measure the phase frequency response as required, for example, by the technical
guidelines "Stereo Encoders for the Pilot-tone System" (TR No. 5/3.2) and "VHF/FM
Radio Broadcasting Transmitters" (TR No. 5/3.1). These specifications require meas-
urement of the phase response in the baseband (see 5.4.2.2).
The phase response of the transmitter's transfer function influences crosstalk in the
stereo channels. In the past, measuring the frequency phase response required a
great deal of effort. For that reason, the decision was frequently made to merely meas-
®
ure the effects (the crosstalk) instead. Nevertheless, the R&S ETL makes it easy to
measure the phase response directly, which then makes it possible to analyze what is
causing the crosstalk.
The technical guidelines cited above stipulate that the phase tolerance is to be meas-
ured using a reference frequency of 500 Hz (or 57 kHz for the additional RDS signal).
Nonetheless, at a reference frequency of 500 Hz, the highpass filter at the transmitter
input causes a residual phase shift, even when the cutoff frequency is very low. That,
in turn, leads to a downward tendency in the measured curve (see Fig. 31, left), which
makes it appear that the limits are not being maintained when the frequencies are high.
In such cases, Rohde & Schwarz recommends measuring the phase response with a
higher reference frequency (such as 5 kHz), which leads to a horizontal curve progres-
sion (see Fig. 31, right).

ured phase response up to 100 kHz with a reference frequency of 500 Hz (left) or 5 kHz (right).
It is also possible, for instance, to measure the phase in the L and R signals (which is
equivalent to the audio phase response; see 5.4.2.1). The specifications "VHF/FM
Radio Broadcasting Transmitters" (TR No. 5/3.1) and "Stereo Encoders for the Pilot-
tone System" (TR No. 5/3.2) do not required that.
Measurements
5.4.2.1 Audio Phase Response
Procedure: Audio phase response

®
Method 1: Method 2:
MEAS→Audio Analysis→Frequency Response→Frequency Response Setup:
Demodulator:
Audio Generator:
 Connector Config: Set to match the transmitter (see 3.2.3)
1
 Level: For example, −2.1 dBu (see tion
40 kHz
transmitter's preemphasis setting
 Response Type: Phase
 Ref Freq: For example, 5 kHz
 Sweep: Linear

2
Sweep Points 100
Set MEAS→Audio Analysis→Frequency Response→Diagram Range→Phase Range
so that the entire phase response is clearly visible.
In the results table, read the values for any nonconformance in the phase response
(see Fig. 32). Use PRINT to generate a printout of the measurement screen as need-
ed.
1
4.4) – for the transmitter's target operating parameters to be set correctly under ”DUT
Parameters“.
2
Measurements

ured phase response of L&R signal with a reference frequency of 5 kHz; maximum positive / negative
variance from the ideal phase response in the table.
Measurements
5.4.2.2 Baseband Phase Response
Procedure: Baseband phase response

®
MEAS→Audio Analysis→Frequency Response→Frequency Response Setup:
Demodulator:
Audio Generator:
1
 Level: For example, 6 dBu (see tion
40 kHz
 Response Type: Phase
 Ref Freq: For example, 5 kHz
 Sweep: Linear

2
Sweep Points 100
Set MEAS→Audio Analysis→Frequency Response→Diagram Range→Phase Range
so that the entire phase response is clearly visible.
In the results table, read the values for any nonconformance in the phase response
(see Fig. 33). Use PRINT to generate a printout of the measurement screen as need-
ed.
1
Parameters“.
2
Measurements

ured phase response of the MPX signal up to 100 kHz the 5 kHz reference frequency; maximum
1
positive / negative variance from the ideal phase response in the table.
1
Measurements
Frequency Response - Balance
5.4.3 Balance
The difference in the amplitude-frequency responses for the right and left channels is
referred to as balance. The individual frequency responses are measured with the
RMS detector.
Procedure: Balance
®
Method 1: Method 2:
MEAS→Audio Analysis→Frequency Response→Frequency Response Setup,
(see Fig. 34)
Demodulator:
mitter's preemphasis
Audio Generator:
1
 Level: For example, −2.1 dBu (see tion
40 kHz
transmitter.
 Response Type: Balance (rms)
 Sweep: Linear

2
Sweep Points 100
1
Parameters“.
2
Measurements

In the results table, read the values for any nonconformance in the balance (see
When audio generator type "MPX (Option B201)" or "Analog (1,L 2,R)" is used, it is
possible to measure the balance M&S.
Measurements

sponse→Frequency Response Setup: Configuration for measuring the balance.

ured balance; maximum positive / negative variance in the table.
Measurements
Stereo Crosstalk
5.5 Stereo Crosstalk

The undesired transmission of the L and R signals from each of those two channels
into the other is known as stereo crosstalk. To perform the measurement, the first step
is to feed in an L input signal and measure the frequency deviation in the R signal.
After that, an R signal is fed in, and the frequency deviation is measured in the
L signal.
®
To measure the stereo crosstalk, the R&S ETL makes – in line with IEC 244-13 –
three possibilities available, which can be selected for the "Crosstalk Setup" under the
"Crosstalk Type" (see Fig. 36):
● Linear:
With linear crosstalk, a ratio is formed out of the RMS value for the modulation sig-
nal at the output of the modulated channel and the RMS value for the fundamental
at the output of the unmodulated channel. This ratio is then indicated in dB.
If, for example, the amplitude of the R signal in the M and S signals does not
match (as the result of linear distortion), the R signal's component is no longer
completely canceled out through formation of L=M+S. In such cases, linear cross-
talk has produced the components contained in the L signal that remain because
of the inequality of the R signal.
● Nonlinear:
In the case of nonlinear crosstalk, the system measures harmonics from sum sig-
nal M in the difference signal S (total harmonic distortion) and intermodulation from
the difference signal S in the sum signal M (difference frequency distortion), which
determines the non-linear distortions. In addition, because of the measurement
principle, noise is also measured.
● Linear and nonlinear combined:
When the sum is derived from both linear and nonlinear crosstalk, this is also re-
ferred to as crosstalk attenuation or stereophonic channel separation.
In line with IEC 244-13, it makes sense to measure the combined linear and nonlinear
crosstalk or to measure these two components separately as linear crosstalk and
nonlinear crosstalk.
®
For measuring the crosstalk on the SCA channel, the R&S ETL offers the possibility of
using an imaginary channel as a reference (Ref Dev).
IEC 244-13 specifies that stereo crosstalk be measured with preemphasis turned on
and with a constant frequency deviation. With conventional measuring equipment,
accomplishing that can require a great deal of effort, because it is necessary to recal-
®
culate and enter the audio level for each frequency. The R&S ETL performs that task
for you. To configure the device for that, it is necessary to select the "Desired DUT
Deviation" and activate "Preemphasis Comp" (see Method 1).
Due to the significant effort required for performing a measurement using a constant
frequency deviation, until now, test technicians have often performed the measure-
ments using a constant level instead. Method 2 shows the configuration for doing that.
Measurements
Stereo Crosstalk
Procedure: Stereo crosstalk

®
Method 1:
Method 2:
With a constant frequency deviation
With a constant level
(in line with IEC 244-13)
MEAS→Audio Analysis→Crosstalk→Crosstalk Setup (see Fig. 36):
Demodulator:
 Deemphasis: Off  Deemphasis: Set to match the trans-
Audio Generator:
 Ampl Definition: Desired DUT Devia-  Ampl Definition: Level
tion
1  Level: For example, –2.1 dBu (see
 Desired DUT Dev: For example, Appendix A)
75 kHz
transmitter
 Crosstalk Type: Linear and Nonlinear combined
 Reference: R&L
 Sweep: Linear
 Sweep Points 100
2
If necessary, set the MEAS→Audio Analysis→Crosstalk→Diagram Range→Crosstalk
Range and Ref Position so that the trace is clearly visible.
In the results table, read the values for stereo crosstalk (see Fig. 37). Use PRINT to
generate a printout of the measurement screen as needed.
If you intend to measure the crosstalk from the M channel and S channel, it is neces-
sary to use ports 1/L and 2/R; furthermore, in the "Audio Generator Setup" under
"Type", you must select "Analog (1/L, 2/R)". After that, the "Crosstalk Setup" under
"Signal Path" offers the options M, S or M&S.
1
Parameters“.
2
Measurements
Stereo Crosstalk
Fig. 36: "TV/Radio Analyzer/Receiver" mode, MEAS→Audio Analysis→Crosstalk→Crosstalk Setup:

Configuration of the measurement for stereo crosstalk according to Method 1.
Fig. 37: "TV/Radio Analyzer/Receiver" mode, MEAS→Audio Analysis→Crosstalk: Measured stereo

crosstalk; max. value in the table.
Measurements
Nonlinear Distortion - Total Harmonic Distortion (THD)
5.6 Nonlinear Distortion
5.6.1 Total Harmonic Distortion (THD)
Total harmonic distortion is a measure of nonlinearity distortion. It indicates the extent

to which the overall signal is made up of undesired harmonics and is specified as a
percentage or in dB. According to IEC 244-13, for this, the RMS values for all harmon-
ics (d2, d3, …) are set in relation to the sum of the RMS value for the fundamental and
the RMS values for all harmonics:
∑
√
∑
Besides that definition, there is another definition, according to which the RMS values
for all harmonics (d2, d3, …) are set in relation to the RMS value for the fundamental:
®
As is the case with most analyzers, the implementation realized in the R&S ETL corre-
sponds to Definition 1. In the case of the distortion that arises in practice, both defini-
tions lead to the same results.
The voltages for the harmonics – and thus their influence on the overall harmonic
distortion – decrease as the order increases.
®
For the measurement of the overall harmonic distortion, the R&S ETL offers two
measured values, which are displayed on the results screen:
 THD: For the sum of the harmonics, the first eight harmonics (d2-d9) are meas-
ured selectively and added together.
 THD+N (Total Harmonic Distortion + Noise): For the sum of the harmonics, the
individual harmonics are not measured selectively; instead, the overall RMS
after the suppressed fundamental up to the cut-off frequency (15 kHz) is used
as the sum for the harmonics. This captures all harmonics up to the cut-off fre-
quency. Nevertheless, this measurement also captures all other forms of inter-
ference, such as noise and intermodulation (much as is the case with nonline-
ar stereo crosstalk; see 5.5).
Measurements
5.6.1.1 THD – Audio
IEC 244-13 specifies that the harmonic distortion is to be measured with preemphasis
turned on. The input frequency is to be varied between 40 Hz and 7.5 kHz. The fre-
quency deviation is to be kept constant for the different input frequencies. The
®
R&S ETL performs the complex level calculations that are required for this because of
the fact that preemphasis is turned on. Using "Desired DUT Deviation" and
"Preemphasis Comp" makes it possible to enter the desired frequency deviation direct-
ly.
Procedure: THD – Audio

®
MEAS→Audio Analysis→THD→THD Setup:
Demodulator:
 Deemphasis: Off
Audio Generator:
 Freq: For example, set to 40 Hz, 500 Hz, 5 kHz and 7.5 kHz one after the
other
 Ampl Definition: Desired DUT Deviation1
 Preemphasis Comp: Set to match the transmitter's preemphasis setting
 Unit: dB or %2
MEAS→Audio Analysis→THD→Diagram Range→Auto Range
In the results table, read the THD values (see Fig. 38). Use PRINT to generate a
printout of the measurement screen as needed.
1
Parameters“.
2
Depending on how you want to display the results.
Measurements
Fig. 38: "TV/Radio Analyzer/Receiver" mode, MEAS→Audio Analysis→THD: Measuring the total
harmonic distortion at 500 Hz.
Measurements
5.6.1.2 THD – Baseband
When performed in line with the technical guideline "VHF/FM Radio Broadcasting
Transmitters" (TR No. 5/3.1), the measurement is taken without a stereo encoder or
decoder.
Procedure: THD – baseband

®
MEAS→Audio Analysis→THD→THD Setup:
Demodulator:
Audio Generator:
 Freq: Set to the selected frequency
 Ampl Definition: Desired DUT Devia-  Ampl Definition: Level
tion
1  Level: For example, −2.1 dBu (see
 Desired DUT Dev: For example, Appendix A)
75 kHz
transmitter
 Unit: dB or %2
MEAS→Audio Analysis→THD→Diagram Range→Auto Range
In the results table, read the THD value. Use PRINT to generate a printout of the
measurement screen as needed.
1
Parameters“.
2
Depending on how you want to display the results.
Measurements
Nonlinear Distortion - Dual Frequency Distortion (DFD)
5.6.2 Dual Frequency Distortion (DFD)
Dual frequency distortion is a measure of undesired second and third-order nonlinear

distortion. It is expressed as percentage or as a ratio in dB. This measurement is
based on the technique of using two signals – f1 and f2 – of the same amplitude with a
frequency spacing of 1 kHz. This leads to quadratic distortion (of the second order)
representing the difference frequency distortion (f 2 – f1 = 1 kHz) and the sum frequency
distortion (f1 + f2). In addition to second-order products (depending on the measure-
ment specification: d2 = f1 – f2 or d2 = f1 – f2 & f1 + f2) , the third-order intermodulation
products (d3 = 2f2 – f1 & 2f1 – f2) are also important here:
–
– log ( )
–
( )
( )
5.6.2.1 Audio Intermodulation
IEC 244-13 specifies that the exciter's preemphasis is to be turned on, that the input
frequency is to be varied, and that the signals' input level is to be selected so that the
signal components generate the same deviation. Entering the individual signal levels
®
for the two-tone signal on the R&S ETL is not necessary. The signal levels are auto-
matically set so that, together, they result in the desired frequency deviation or level
that was entered and so that each signal component generates the same frequency
deviation.
Unlike IEC 244-13 (Method 1 in the section below) the technical guideline "Stereo
Encoders for the Pilot-tone System" (TR No. 5/3.2) requires that the measurement be
performed with preemphasis or deemphasis (Method 2 in the section below).
It must be ensured that, during measurement of audio intermodulation (signal path:

L&R) the upper cut-off frequency is 15 kHz. Intermodulation influences that arise above
this cut-off frequency are not reflected in the results. The measured intermodulation
products (in dB) refer to the measured frequency deviation of .
Measurements
Procedure: Audio intermodulation

®
Method 1: Method 2:
Preemphasis turned on Preemphasis turned of
(in line with IEC 244-13) (in line with TR 5/3.2)

On the transmitter, turn on preemphasis. On the transmitter, turn off preemphasis.
MEAS→Audio Analysis→DFD→DFD Setup:
Demodulator:
 Deemphasis: Off
Audio Generator:
 Waveform: Dual Tone, constant spacing
 Upper Freq: For example, 6 kHz
 Freq Spacing 1 kHz

1
Ampl Definition: Desired DUT Deviation
 Preemphasis Comp: Set to match the  Preemphasis Comp: Off
transmitter's preemphasis
 Unit: dB or %
In the table of results, read the values for the intermodulation products (d 2 and d3; see
1
Parameters“.
Measurements
Fig. 39: "TV/Radio Analyzer/Receiver" mode, MEAS→Audio Analysis→DFD: Measurement of dual-

frequency distortion (DFD) with the upper frequency (f2) 6 kHz.
5.6.2.2 Intermodulation in the Baseband (up to 100 kHz)
IEC 244-13 specifies that the exciter's preemphasis is to be turned off, that the input
frequencies are to be varied, and that the signals' input levels are to be selected so
that the signal components have the same amplitude. It is not necessary to enter the
®
individual signal levels for the two-tone signal on the R&S ETL. The signal levels are
automatically set so that, together, they result in the desired frequency deviation or
level that was entered and so that each signal component generates the same fre-
quency deviation. The frequency deviation for the different input frequencies is to be
®
kept constant. The R&S ETL enables you to either enter the audio level or enter the
corresponding frequency deviation. Both configurations lead to the same result.
The technical guideline "VHF/FM Radio Broadcasting Transmitters" (TR No. 5/3.1)
specifies that the measurement is to be taken in the frequency range from 15 kHz to
76 kHz.
It must be ensured that, during measurement of intermodulation in the baseband

("Signal Path: MPX") the upper cut-off frequency is 100 kHz. Intermodulation products
that arise above this cut-off frequency are not reflected in the results. The measured
intermodulation products (in dB) refer to the measured frequency deviation of .
Measurements
Procedure: Intermodulation in the baseband

®
MEAS→Audio Analysis→DFD→DFD Setup:
Demodulator:
 Deemphasis: Off
Audio Generator:
 Waveform: Dual Tone, constant spacing
 Upper Freq: For example, 16 kHz, 26 kHz, 41 kHz, 51 kHz, 76 kHz
 Freq Spacing 1 kHz
1
 Level: For example, 6 dBu tion
40 kHz
 Unit: dB or %
In the table of results, read the values for the intermodulation products (d 2 and d3; see
1
Parameters“.
Measurements
Fig. 40: "TV/Radio Analyzer/Receiver" mode, MEAS→Audio Analysis→DFD: Measurement of dual-

1
frequency distortion (DFD) with the upper frequency (f2) of 16 kHz.
1
Measurements
5.6.2.3 Intermodulation at 57 kHz
In the technical guidelines "VHF/FM Radio Broadcast Transmitters" (TR No. 5/3.1) and
"VHF/FM Rebroadcast Receivers" (TR No. 5/3.5), the measurement of the intermodu-
lation is performed using these input frequency pairs: 6.2 kHz and 31.6 kHz as well as
9.3 kHz and 47.7 kHz. Here, the intermodulation products at 57 kHz are to be ana-
lyzed:
f1 = 6.2 kHz, f2 = 31.6 kHz: d3 = 2·f2 – f1 = 57 kHz
f1 = 9.3 kHz, f2 = 47.7 kHz: d2 = f1 + f2 = 57 kHz
In each case, the guidelines require a frequency deviation of ±22.5 kHz or ±10 kHz,
®
respectively. Since the overall frequency deviation is entered on the R&S ETL, the
value entered here must be 45 kHz or 20 kHz. TR 5/3.1 stipulates that the intermodula-
tion products be referenced to a calculated frequency deviation of 40 kHz. Since the
reference to a calculated frequency deviation is a special case, the intermodulation
®
products are not measured using the R&S ETL's DFD function (which references the
intermodulation products to the measured frequency deviation); instead, they are
measured in the audio spectrum.
Procedure: Intermodulation at 57 kHz

®
MEAS→Modulation Analysis→Audio Spectrum→Audio Spectrum Setup:
MEAS→Modulation Analysis→Audio Spectrum→Audio Generator→
Audio Generator Setup
 Signal: AF
 Waveform: Dual Tone, independent frequencies
 Freq 1: 6.2 kHz or 9.3 kHz
Freq 2: 31.6 kHz or 47.7 kHz
 Ampl Definition: Desired DUT Deviation
1
 Desired DUT Dev: For example, 20 kHz or 45 kHz

MKR→Marker 1: 57 kHz
TRACE→Trace Mode: Average
MEAS→Modulation Analysis→Audio Spectrum→Diagram Range→Ref Deviation:

40 kHz
Read the measured marker value (see Fig. 41). Use PRINT to generate a printout of
the measurement screen as needed.
1
Parameters“.
Measurements
Fig. 41: "TV/Radio Analyzer/Receiver" mode, MEAS→Modulation Analysis→Audio Spectrum: Meas-

1
urement of intermodulation products at 57 kHz using the marker function (top right).
1
Measurements
Spurious Modulation (Signal-to-Noise Ratio, S/N) - Spurious Frequency Modulation
5.7 Spurious Modulation (Signal-to-Noise Ratio, S/N)

For the signal-to-noise ratio, a differentiation is made between the spurious frequency
modulation and spurious amplitude modulation. The higher the S/N value is, the higher
the signal quality. The signal-to-noise ratio is defined as the ratio of the audio signal
(wanted signal) to noise, and it is expressed in dB:
5.7.1 Spurious Frequency Modulation
5.7.1.1 Unweighted and Weighted Noise Voltage
IEC 244-13 specifies that the unweighted and the weighted noise voltage be measured
using a QPK detector. In the weighted measurement of the noise voltage, the ITU-R
BS.468-4-compliant filter is also used. This filter accounts for the effects that noise has
on the human ear and provides the best possible representation of these requirements
from a T&M perspective.
Besides the QPK detector, which also takes the effects on the human ear into account,
®
the R&S ETL also makes it possible to perform the measurement with an RMS detec-
tor. The test specifications stipulate which detector is to be used for measurement.
The test specification stipulates which frequency deviation is to be used to generate

the signal when measuring the signal-to-noise ratio. That means that the signal ampli-
tude ( ) is predefined and does not have to be measured separately; measure-
ment of the incidental deviation ( ) is sufficient. Measuring the signal amplitude
would cause the results to be overdetermined.
®
With the R&S ETL, is calculated using the data entered in the "DUT Parame-
ters" (see 3.1.5) and the reference deviation (frequency deviation from the test specifi-
cation). When entering the "Deviation" under "DUT Parameters", it is important to
®
ensure that the peak deviation is always entered on the R&S ETL. Prior verification of
the transmitter's modulator constant (see 5.3) ensures that a measurement of
leads to the same value as to the one that was determined through calculations.
®
If the FM noise voltage is measured with the R&S ETL for channels L and R in combi-
nation ("Signal Path: L&R"), the user must select whether the measurement will be
weighted or unweighted ("Weighting Filter ITU-R BS.468-4"). If the channels are
measured sequentially ("Signal Path: L " or "Signal Path: R") both values are always
shown.
Measurements
The section below provides an example of the settings for measuring the left channel.
Procedure: Unweighted and weighted noise voltage

®
On the transmitter, turn on preemphasis .
MEAS→Audio Analysis→ S/N→S/N Setup (see Fig. 42).
Demodulator:
 Signal Path: L
 Deemphasis: Set to match the transmitter's preemphasis setting
Audio Generator:
 Signal: Off
 No configuration of the signal (such as "Waveform", "Ampl Definition") is
necessary, because the signal is not measured
 Ref Deviation: Frequency deviation of the reference audio signal, for ex-
ample: 40 kHz
MEAS→Audio Analysis→S/N: Read the measured values (see Fig. 43).
Fig. 42: “TV/Radio Analyzer/Receiver" mode, MEAS→Audio Analysis→S/N→S/N Setup: Configuration

for measuring the spurious frequency modulation.
Measurements
Fig. 43: "TV/Radio Analyzer/Receiver" mode, MEAS→Audio Analysis→S/N: Unweighted and weighted
signal-to-noise ratio for the L channel in the 2nd/3rd line.
Measurements
5.7.1.2 Periodic Noise Voltage
Periodic noise includes all discrete, unwanted interference frequencies within the audio
frequency band. It is the ratio, expressed in dB, between an unwanted component and
a reference level or reference deviation.
Besides offering capabilities for using markers to perform manual investigations within
®
the spectrum, the R&S ETL also supports the automatic generation of a list of all
peaks. Here, it is also possible to configure the device for certain additional conditions
(such as frequency above 150 Hz or Peak > –80 dB). The user can sort the list accord-
ing to frequency or level.
Procedure: Periodic noise

®
MEAS→Modulation Analysis→Audio Spectrum→Audio Generator→Audio Generator
Setup:
 Signal: Off
 No configuration of the signal (such as "Waveform", "Ampl Definition") is
necessary, because the signal is not measured
MEAS→Modulation Analysis→Audio Spectrum→Audio BW: 20 Hz
MEAS→Modulation Analysis→Audio Spectrum→Diagram Range→Ref Deviation: For

example, 40 kHz
Set MEAS→Modulation Analysis→Audio Spectrum→Diagram Range→Ref Position:
so that the signal is clearly visible (for instance, 130 %).
TRACE→Trace Mode→Average
MKR→More→Marker Peak List
MKR→More→Marker Peak List→Left Limit: For example, 150 Hz
MKR→More→Marker Peak List→Threshold: For example, 80 Hz
MKR→More→Marker Peak List
Read the measured peak value (see Fig. 44). Use PRINT to generate a printout of the
measurement screen (see Fig. 45.) as needed.
Measurements
Fig. 44: "TV/Radio Analyzer/Receiver" mode, MEAS→Modulation Analysis→Audio Spectrum: List of

the periodic noise voltages (Peak List: MKR→More→Marker Peak List) greater than −105 dB (right).
Fig. 45: "TV/Radio Analyzer/Receiver" mode, MEAS→Modulation Analysis→Audio Spectrum: Period-

1
ic noise voltage in the spectrum with a limit greater than –105 dB.
1
Measurements
Spurious Modulation (Signal-to-Noise Ratio, S/N) - Spurious Amplitude Modulation
5.7.2 Spurious Amplitude Modulation
The configuration for measuring the spurious amplitude modulation depends on the
specific test specification. IEC 244-13 specifies that the measurement be performed
with a PK detector and without a band limitation. Measurements performed in line with
ETSI EN 302 018-1 are also made with a PK detector, but with the band limited to
20 kHz. Measurements performed in line with TR 5/3.1 are taken with and without a
ITU-R 468 wtd-compliant weighting filter with a QPK detector and with the band limited
®
to 20 kHz. The R&S ETL supports all four of these configurations.
The spurious amplitude modulation measurement ist taken without FM modulation.

Here, a modulation depth ("Mod Depth") of 100 % is assumed as the reference.
5.7.2.1 Spurious Amplitude Modulation without Input Signal
For the spurious amplitude modulation, the peak voltage at the output of a linear enve-
lope detector is measured without a modulation signal. The result is expressed as a
percentage of the envelope detector output's direct current component.
Procedure: Spurious amplitude modulation without input signal

®
MEAS→Audio Analysis→ S/N→S/N Setup:
Demodulator:
 Signal Path: AM
 Deemphasis: Off
Audio Generator:
 Signal: Off
 No configuration of the signal (such as "Waveform" or "Ampl Definition")
is necessary, since the signal is turned off
 Ref Mod Depth: Permanently set to 100 %.
Measurements
Fig. 46: "TV/Radio Analyzer/Receiver" mode, MEAS→Audio Analysis→S/N: Spurious amplitude

modulation as required by IEC 244-13 in line 1, by ETSI EN 302 018-1 in line 2 and by TR 5/3.1 (with
1
and without filter) in line 3/4.
1
Measurements
5.7.2.2 Synchronous Amplitude Modulation
The synchronous amplitude modulation is measured with FM modulation. It is a meas-

ure for the FM-AM conversion using, for example, the RF frequency response in the
transmitter.
Procedure: Synchronous amplitude modulation

®
MEAS→Audio Analysis→ S/N→S/N Setup:
Demodulator:
 Signal Path: AM
 Deemphasis: Off
Audio Generator:
 Signal: AF
 Freq: For example, 500 Hz
 Ampl Definition: Desired DUT  Ampl Definition: Level
Deviation
1  Level: For example, 6 dBu (see Ap-
 Desired DUT Dev: For example, pendix A)
40 kHz
 Ref Mod Depth: Permanently set to 100 %.
MEAS→Audio Analysis→S/N: Read the measured values.
1
Parameters“.
Measurements
Spurious Modulation (Signal-to-Noise Ratio, S/N) - Noise Power Density at 57 kHz
5.7.3 Noise Power Density at 57 kHz
The technical guideline "VHF/FM Radio Broadcasting Transmitters" (TR No. 5/3.1)
demands that the noise power density measured at the output of a measurement
modulator that has been realized in line with TR 5/3.4 and is terminated with 600 Ω is
not greater than –100 at 57 kHz. This measurement ensures that the signal-to-
noise ratio in the RDS channel is sufficient.
Due to the load impedance of 600 Ω, the noise power results in a voltage. Depending
on that voltage and on the modulation constant, a certain deviation arises. Thus, the
measured quantity that actually exists in physical form at the transmitter output is not
the noise power density, but rather the "noise deviation density." TR 5/3.1, therefore,
describes an indirect measurement of the "noise deviation density" as the noise power
density at the output of a special test configuration (a demodulator constant of 6 dBu
for 40 kHz deviation, load impedance of 600 Ohm). Since this test configuration has
not been standardized internationally, the measurement results achieved in this way
are not valid everywhere.
®
For this reason, the R&S ETL employs a different approach. Without any detours, the
"noise deviation density" is set in direct relation to a reference deviation (the audio
spectrum analyzer's reference deviation). This result offers the advantage of general
validity and is independent of a specific test setup.
The difference between these two methods lies in the dimension of the output quantity.
As defined by TR 5/3.1, the noise power density describes the quotient of the noise
power and bandwidth, referenced to 1 mW (dB , reduced to ). The "noise
®
deviation density" for the R&S ETL, on the other hand, describes the quotient of the
1
RMS noise deviation and the square of the bandwidth , set in relation to the reference
deviation (dB ( ), reduced to ). These two quantities can be converted
√ √
back and forth:
log ( )
log ( ) log )
√ √
Where
In practice, it is possible to avoid the conversion by simply setting the appropriate

®
reference deviation on the R&S ETL. The displayed deviation density in (refer-
√
enced to the reference deviation) corresponds to the noise power density in , when
the reference deviation is selected so that 0 dBm would arise on the required resistor.
Therefore, at a reference deviation of 40 kHz – which causes 6 dBu to be present at a
600 Ohm resistor (as required by TR 5/3.1) – it would be necessary to enter 20 kHz
(which corresponds to 0 dBm at 600 Ohm) as the reference deviation.
1
For the square of the bandwidth, the physically correct unit √ can be derived by
converting the power density to the "voltage density":
̃ [ ] √̃ [ ] [ ] or with SI units: ̃ [ ] √̃ [ ] [ ]
√ √
Measurements
The numerical value of the displayed "noise deviation density" then corresponds to the
noise power density as defined by TR 5/3.1.
Procedure: Noise power density at 57 kHz

®
MEAS→Modulation Analysis→Audio Spectrum→Audio Generator→
Audio Generator Setup:
Audio Generator:
 Signal: OFF
 No configuration of the signal (such as "Waveform" or "Ampl Definition")
is necessary, because the signal is turned off
MEAS→Modulation Analysis→Audio Spectrum→Diagram Range→Ref Deviation: For
example, 20 kHz
MEAS→Modulation Analysis→Audio Spectrum→MKR→More→Noise Meas: On
MKR→Marker 1: 57 kHz
TRACE→Trace Mode→Average
Read the marker value (see Fig. 47). Use PRINT to generate a printout of the meas-
urement screen as needed.
Measurements
Fig. 47: "TV/Radio Analyzer/Receiver" mode, MEAS→Modulation Analysis→Audio Spectrum: Noise

1
power density at 57 kHz.
1
Measurements
Polarity of the Input
5.8 Polarity of the Input

This measurement is used to check to see if driving the system with a positive instan-
taneous value for the input signal causes a frequency increase in the output frequency.
®
It is easy to check this with the R&S ETL by feeding in two audio tones, whereby the
following must be valid: f2 = 2·f1. Since the phases of these signals are generated in
sync, a superposition occurs in which the absolute value of the positive peak values is
greater than the absolute value of the negative peak values (see Fig. 48).
Fig. 48: Superposition of the signals generated with a synchronous phase leads to a signal for which
the absolute value of the positive peak is larger than that of the negative peak.
Measurements
The section below specifies the settings for testing the left channel. The right channel
can be verified in the same way. When the polarity is only reversed for only one of the
channels, the M and S signals are switched, and mono receivers will remain "mute." L
and R must be tested separately; otherwise, it would not be possible to establish the
fact that the polarity has been reversed for both inputs.
Procedure: Polarity of the input

®
On the transmitter, turn off preemphasis.
MEAS→Modulation Analysis→Audio Scope→Audio Generator→
Audio Generator Setup (see Fig. 49):
Audio Generator:
 Signal: L
 Waveform: Dual Tone, independent frequencies
 Freq 1: For example, 500 Hz
 Freq 2: For example, 1 kHz
1
 Level: For example, 6 dBu (see tion
40 kHz
MEAS→Modulation Analysis→Audio Scope→Audio Scope Setup:
 Signal Path: L
MEAS→Modulation Analysis→Audio Scope→Diagram Range→Trigger Level: Set this
parameter to a value that results in a steady image; for example, 30 Hz.
Check to see if the absolute values of the positive peak value is greater than the
absolute value of the negative peak values (see Fig. 50); if it is greater, the polarity is
not reversed.
1
Parameters”.
Measurements
Fig. 49: "TV/Radio Analyzer/Receiver" mode, MEAS→Modulation Analysis→Audio Scope→Audio

Generator→Audio Generator Setup: Configuration for checking the polarity.
Fig. 50: "TV/Radio Analyzer/Receiver" mode, MEAS→Modulation Analysis→Audio Scope: When a

dual tone is being fed in with f2 = 2·f1, the absolute value of the positive peak value (+Peak) is greater
than the absolute value of the negative peak value (–Peak), if a positive instantaneous value for the
input signal causes a frequency increase.
Measurements
Digital Input Signal (AES/EBU)
5.9 Digital Input Signal (AES/EBU)

Most transmitters also make an AES/EBU input available that can be used to feed
digital audio signals (stereo or mono) into the transmitter. To test the AES/EBU input, it
is possible to repeat the measurements that were made for the L&R inputs – such as
the measurements for the amplitude-frequency response (5.4.1.1) and stereo crosstalk
(5.5), for instance. The question of which measurements should be performed again
needs to be decided on an individual basis depending on the specific circumstances.
This section will not repeat the details for configuring the individual measurements.
Instead, it will only described the differences and special considerations.
To perform the measurements, the transmitter input is set to "AES Stereo", and the
® ®
R&S ETL's AES encoder is used. To use the R&S ETL's AES encoder, the user
selects the "AES/EBU (Option B201)" as the "Audio Generator Type". To match the
transmitter's AES input, the "Impedance" is set to 75 Ω or 110 Ω (see Fig. 51). The
signal level for AES/EBU is expressed in dBFS. As an alternative, it is possible to enter
the desired frequency deviation by selecting "Desired DUT Deviation" under "Type". To
test the AES/EBU input, these adapted settings can be used to repeat all of the meas-
urements that have been described up until this point.

sponse→Frequency Response Setup: Configuration for measuring the audio amplitude-frequency
response for the transmitter's AES/EBU input.
Measurements
Digital Input Signal (AES/EBU)
During the phase measurement, observations could reveal that the characteristic is
marked by triangular outliers (see Fig. 52). This is due to the fact that the instantane-
ous variance in the regeneration of the timing frequency for some AES encoders is too
great; as a result, the phase "runs off" during the measurement and has to be correct-
ed frequently.
Fig. 52: "TV/Radio Analyzer/Receiver" mode, MEAS→Audio Analysis→Frequency Response: Audio

phase frequency for the transmitter's AES/EBU input.
Abbreviations
6 Abbreviations
AES/EBU Audio Engineering Society/European Broadcasting Union
AF Audio frequency
AM Amplitude modulation
ARI Autofahrer-Rundfunk-Information (German wireless information service for car drivers)
CCIR Comité Consultatif International des Radiocommunications
DARC Data Radio Channel
FFT Fast Fourier transform
FM Frequency modulation
IRT Institut für Rundfunktechnik
IEC International Electrotechnical Commission
PK Peak
QPK Quasi-Peak
RDS Radio Data System
RMS Root mean square
SCA Subsidary Communication Authorization

Technical guidelines for Germany's public broadcasters (Technische Richtlinien der öffentlich-
TR rechtlichen Rundfunkanstalten in der Bundesrepublik Deutschland)
7 Auxiliary Information
Our application notes are regularly revised and updated. Check for any changes at
http://www.rohde-schwarz.com.
Please send any comments or suggestions about this application note to
Ordering Information
8 Ordering Information
Designation Type Order No..
Instrument
TV Analyzer, 500 kHz to 3 GHz, with tracking generator R&S®ETL 2112.0004.13

1 ®
Average Power Sensor; 9 kHz to 6 GHz, 200 mW R&S NRP-Z91 1168.8004.02
Required options
FM (radio) Firmware R&S®ETL-K110 2112.0410.02
FM (radio) Audio Analyzer/Generator R&S®ETL-K111 2112.0427.02
DTV, ATV, FM Universal Interface R&S®ETL-B201 (MOD3) 2112.0304.03

®
RF Preselector R&S ETL-B203 2112.0327.03
One of the following two FM frontends:
 High SNR FM frontend R&S®ETL-B110 2112.0233.02

®
 FPGA External Board, High SNR FM R&S ETL-B310 2112.0340.02
1
Power Sensor Support with NRP R&S®FSL-K9 1301.9530.02
1
One of the following three power sensor interfaces
 Additional interfaces R&S®FSL-B5 1300.6108.02

®
 Active USB Adapter R&S NRP-Z3 1146.7005.02
 Passive USB Adapter R&S®NRP-Z4 1146.8001.02
1
Only for measuring the transmitter output level when an accuracy better than 1 dB is
required.
Input Level and Frequency Deviation
Overview in Tables
A Input Level and Frequency Deviation
A.1 Overview in Tables

The following tables show the audio level that must be entered in order to generate a
desired frequency deviation at 15 kHz. The transmitter configurations used here (nom-
inal level of 6 dBu and nominal deviation of 40 kHz or 50 kHz) cover the most com-
monly used FM transmitter configurations. If other configurations are required, they can
be calculated easily using the corresponding formulas (see A.2).
Nominal deviation of 40 kHz, nominal level of 6 dBu

Desired devia-
tion [kHz] at
15 kHz
Audio level without Audio level Audio level

preemphasis Preemphasis 50 µs Preemphasis 75 µs
[dBu] [V] [dBu] [V] [dBu] [V]

20 0 0.77 –13.6 0.16 –17 0.11
25 1.9 0.97 –11.7 0.20 –15.1 0.14
40 6 1.55 –7.6 0.32 –11 0.22
50 7.9 1.93 –5.7 0.40 –9.1 0.27
75 11.5 2.90 –2.1 0.60 –5.5 0.41
100 14 3.86 0.4 0.80 –3 0.54
Nominal deviation of 50 kHz, nominal level of 6 dBu

Desired devia-
tion [kHz] at
15 kHz
Audio level without Audio level Audio level

preemphasis Preemphasis 50 µs Preemphasis 75 µs
[dBu] [V] [dBu] [V] [dBu] [V]

20 –2 0.62 –15.6 0.13 –19 0.09
25 0 0.77 –13.6 0.16 –17 0.11
40 4.1 1.24 –9.5 0.26 –12.9 0.17
50 6 1.55 –7.6 0.32 –11 0.22
75 9.5 2.32 –4.1 0.48 –7.5 0.32
100 12 3.09 –1.6 0.64 –5 0.43
Mathematical Correlation Between the Input Level and the Frequency Response
A.2 Mathematical Correlation Between the Input Level

and the Frequency Response
Depending on the country and on the applicable specifications, the input level is either
expressed in dBu or in volts. As a "pseudo" unit of measurement, dBu is a logarithmic
measure of voltage ( √ ). The conversion from
volts to dBu and back is calculated as follows:
[ ] [ ]
[ ] √ – [ ] log –
Setting the transmitter's modulator constant results in the corresponding nominal

deviation for a given nominal level. The nominal deviation also varies in different coun-
tries and specifications. For the calculation to determine which input level has to be set
in the audio generator for a desired deviation, the following relationship applies:
[ ] [ ]
[ ] log ( ) [ ]
For the preemphasis, 50 µs is usually used as the time constant in Europe and Japan,
and 75 µs is used in the US. When preemphasis is turned on in the transmitter, a
frequency-dependent increase arises in the audio level. When entering the value on
the audio generator, it is necessary to compensate for this with a corresponding reduc-
tion.
[ ]
√
Increase in the audio level for a time constant of 50 µs:

Audio 40 100 500 1 5 6 7.5 10 15
frequency Hz Hz Hz kHz kHz kHz kHz kHz kHz
Factor for
the in- 1.00 1.00 1.01 1.05 1.86 2.13 2.56 3.30 4.82
crease
Increase in
0 0 0.1 0.4 5.4 6.5 8.1 10.3 13.6
dB
Increase in the audio level for a time constant of 75 µs:

Audio 40 100 500 1 5 6 7.5 10 15
frequency Hz Hz Hz kHz kHz kHz kHz kHz kHz
Factor for
the in- 1.00 1.00 1.03 1.11 2.56 3.00 3.67 4.82 7.14
crease
Increase in
0 0 0.2 0.8 8.1 9.5 11.3 13.6 17
dB
Example for Calculating the Required Audio Level
A.3 Example for Calculating the Required Audio Level

For a transmitter with a nominal deviation of 50 kHz at an input level of 6 dBu (corre-
sponds to about 1.54 volts), a deviation of 100 kHz is to be achieved. This yields an
audio input level of:
( )
By making the corresponding selections in "Audio Generator Setup" under "Ampl

®
Definition" (see 3.2.5) on the R&S ETL, it is possible to enter the desired peak devia-
tion ("Desired DUT Deviation"), the audio generator level in dBu ("Level") or the audio
generator level in volts ("Peak Voltage"). Consequently, no conversion is required
when "Ampl Definition" is selected.
If a preemphasis of 50 µs is used with this transmitter, the audio level that is entered
must be reduced by a corresponding amount. If the deviation of 100 kHz at a 15 kHz
audio frequency is to be achieved, the audio level must be reduced as follows:
log
√
The audio level to be entered is:
Automated Measurements with R&S®TxCheck
B Automated Measurements with

R&S®TxCheck
® ®
The R&S TxCheck software application is available free of charge on every R&S ETL.
This software makes it possible run measurements automatically, and includes the
®
generation of a weighted report of the results. With the aid of R&S TxCheck, you can
automate the following measurements:
● Transmitter Output Level (5.1)

● Frequency Accuracy (5.2)
● Audio Frequency Characteristic (up to 15 kHz, or 17.5 kHz for Mono Transmitters)
(5.4.1.1)
● Baseband Frequency Characteristic (up to 100 kHz). (5.4.1.2)
● Audio Phase Response (5.4.2.1)
● Baseband Phase Response (5.4.2.2)
● Stereo Crosstalk (5.5)
● Total Harmonic Distortion (THD) (5.6.1)
● Audio Intermodulation (5.6.2.1)
● Intermodulation in the Baseband (up to 100 kHz) (5.6.2.2)
● Digital Input Signal (AES/EBU) (5.9)
This Application Note includes the file "7BM105.ETLtxi". When this file is opened in
®
R&S TxCheck, the software can perform all of the measurements on the transmitter's
L&R input and MPX input that can be automated:
®
Performing Automated Measurements Using R&S TxCheck
®
Copy the file 7BM105.ETLtxi to the R&S ETL.
®
MODE→TxCheck
®
In the R&S TxCheck application, go to File/Open Profile (*.ini) and select the previ-
ously copied profile "7BM105.ETLtxi".
By selecting the “Settings” tab, adjust parameters such as the frequency and transmit-
ter parameters (see Fig. 53).
Set the basic configuration using the "Write Settings to ETL" button.
If necessary, select the "Measurements" tab to adapt the configuration of the individu-
al measurements (such as the "Desired DUT Deviation" and the "Preemphasis Com-
pensation") as well as the limits for the individual measurement parameters (see
Fig. 54).
Go to "Measurement/Start Measurement" to start the measurement.
After the measurements are complete, go to "File/Save" to save the results.
Fig. 53: R&S®TxCheck User Interface, "Settings" tab.
Fig. 54: R&S®TxCheck User Interface, "Measurements" tab.
The results of the automated measurement are displayed in the "Measurements" and
the "Graphics" tabs. To view the saved result files on an external PC, first install the
® ®
R&S TxCheck software on that PC (in the R&S TxCheck application, go to
"Help/Installation Info…" for more information). Finally, go to "File/Print" to print the
result report. (see Fig. 55).
Fig. 55: R&S®TxCheck: Excerpt from the report.
About Rohde & Schwarz
Rohde & Schwarz is an independent group
of companies specializing in electronics. It is
a leading supplier of solutions in the fields of
test and measurement, broadcasting,
radiomonitoring and radiolocation, as well as
secure communications. Established more
than 75 years ago, Rohde & Schwarz has a
global presence and a dedicated service
network in over 70 countries. Company
headquarters are in Munich, Germany.
Environmental commitment
● Energy-efficient products
● Continuous improvement in environ-
mental sustainability
● ISO 14001-certified environmental
management system
Regional contact
Europe, Africa, Middle East
+49 89 4129 12345
customersupport@rohde-schwarz.com
North America
1-888-TEST-RSA (1-888-837-8772)
customer.support@rsa.rohde-schwarz.com
Latin America
+1-410-910-7988
customersupport.la@rohde-schwarz.com
Asia/Pacific
+65 65 13 04 88
customersupport.asia@rohde-schwarz.com
China
+86-800-810-8228 /+86-400-650-5896
customersupport.china@rohde-schwarz.com
This application note and the supplied

programs may only be used subject to the
conditions of use set forth in the download
area of the Rohde & Schwarz website.
R&S® is a registered trademark of Rohde & Schwarz

GmbH & Co. KG; Trade names are trademarks of the
owners.
Rohde & Schwarz GmbH & Co. KG

Mühldorfstraße 15 | D - 81671 München
Phone + 49 89 4129 - 0 | Fax + 49 89 4129 – 13777
www.rohde-schwarz.com

Application Note: Measurements On FM Transmitters For Acceptance, Commissioning and Maintenance

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Measurements on FM

Transmitters for Acceptance,

Despite the advent of advanced digital

The R&S®ETL TV analyzer combines

3 R&S®ETL Settings for FM Measurements .......................... 10

4 Preparatory Steps ................................................................ 23

7 Auxiliary Information ........................................................... 81

8 Ordering Information ........................................................... 82

A Input Level and Frequency Deviation ................................. 83

B Automated Measurements with R&S®TxCheck ................. 86

Despite the advent of advanced digital transmission methods, analog broadcasting

This application note covers the fundamental FM measurements performed during FM

Section 2 briefly describes the basics of FM broadcast technology. Section 3 explains

The Multiplex (MPX) Signal

2.1 The Multiplex (MPX) Signal

The Multiplex (MPX) Signal

Fig. 4: Schematic diagram of an MPX signal spectrum.

Pre- and Deemphasis

2.1 Pre- and Deemphasis

98 % of the spectral power within

99 % of the spectral power within

Fig. 5: RF spectrum of a frequency-modulated 1 kHz audio signal (left) and a frequency-modulated

2.3 Stereo Decoder

2.4 Transmitter Inputs

Audio Engineering SocietyEuropean Broadcasting Union Most of today's advanced

3 R&S®ETL Settings for FM Measurements

Fig. 6: Simplified overview of the analysis functions for acceptance-testing an FM transmitter.

General FM Settings – Radio Settings

3.1 General FM Settings – Radio Settings

Modulation Standard (3.1.1)

Stereo Decoder (3.1.2)

Universal Interface (Option B201) (3.1.4)

DUT Parameters (3.1.5)

General FM Settings – Radio Settings

3.1.1 Modulation Standard

stereo measurement decoder. The audio-frequency bandwidth is limited to

General FM Settings – Radio Settings

Fig. 9: RDS/RBDS decoder.

3.1.2 Stereo Decoder

Pilot Dev Threshold

General FM Settings – Radio Settings

1/L, 2/R Output

Deviation for 6 dBu output level

General FM Settings – Radio Settings

3.1.4 Universal Interface (Option B201)

There are two choices available for output signal assignment:

3.1.5 DUT Parameters

Audio Generator Settings

3.2 Audio Generator Settings

Audio Generator Settings

The following settings are available under "Type":

● MPX (Option 201):

● AES/EBU (Option B201):

Audio Generator Settings

● Analog (1/L, 2/R):

Audio Generator Settings

3.2.3 Connector Config

Depending on the type of measurement, a single-tone or dual-tone signal needs to be

Audio Generator Settings