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MODULATION ANALYZERS analyzers




Characteristics, uses The Frequency-range Extension Option - which can be
retrofitted - extends the frequency range up to 1360 MHz,
The Modulation Analyzer FAM otters a maximumof con.
thus covering practically all radio services.
venience for modulation measurements on AM, FM and
phase-modulated signals. All tunctions being microproc-
Special features The FAM exhibits negligible inherent
essor-controlled,manual operationis reducedto aminimum.
noise and excellent linearity.
Modulationmeasurementsover a range of carrier frequen-
cies from 55 kHz to 1360 MHz are performedmore precisely Residual FM being less than 1 Hz in the basic frequency
end more easlly with the FAM than with previouslyavailable range (proportionallyincreasingabove) with CCITT weight-
equipment. The lEG-bus interface makes the instrument ing and 5 Hz with 20 kHz weightingbandwidth,whilst residual
system-compatibleend suitable tor use in automated test AM is as low as 0.01%. the FAM perrnitsunwantedmodula-
assembties. tion to be measuredprecisely.
Types 01 measurements The ModulationAnalyzercan be The FM stereo noise of FAM model 54, being -72 dB
usedtor measurements otherwisecalling tor up to five differ- referredto 40 kHz deviation,CCIR weightlng,permitsprecise
ent instruments.It features the following capabilities: SI N-ratlorneasurements, say, on FM broadcasttransmitters.
. Measurementof modulation depth, frequency deviation The transmission IInearity of the FAM fulfils the exacting
and phase deviation demands involved in wideband modulation methods used.
tor example, in FM broadcasting. Excellent amplitude and
. Simultaneouscarrier-frequencymeasurementwith 1 Hz
or 10 Hz resolution phase linearity make distortion-freedemodulationof multi-
plex signals possible;see applicationexample on page after
. Measurementof modulationfrequencywith 0.1 Hz reso- next.
lution
Dlstortlon of less than 0.1% and stereo channel separation
. Distortionmeasurementdown to <0.1 %, of 50 dB guarantee accurate results of measurement.
also SINAD indication in dB
. AF vo/tage measurement with weighting filters
(psophometerfunction)
. Evaluationof external AF signals
Unwantedmodulationcan be measuredand weightedaccu-
ratelyon account of switch-selected test bandwidths and
Democ*Jiat8d
standardweighting filters. stereoaignal
av8l8*M
Fjeld of appllcation The basic model covers a carrier- FM~oI
frequency range of 55 kHz to 120 MHz and offers a very ModIMaon
AnaIyzerFAM
economical and high-performance solution tor measuring
tasks in FM and AM broadcastingand certaln radiotelephony
254 and other radio services.
analyzers

Setting, measurement, display Modulation measurement, display The middle section is
used tor setting the type ot modulation and time constant,
The front panel ot the FAM is divided into thr" tunctional
seleding the filter and displayingthe modul8tlon measure-
sedions for easy operation and clear presentation ot the
ment result. An additional,analog display in the form 01 a
results, several parametersbeing displayedsimultaneously:
light spot moving around a clrcle greatly 1acilitatesadjust-
Lefthandsection Carrier-frequency display ments by providingtrend indication.The user simply selects
and entry (with manual tuning) the type 01 modulation - AM, FM or
Middlesection Result display three deemphasistime constants. The ModulationAnalyzer
and setting ot operatingmodes demodulates signals 01 any mode 01 modulation including
simultaneousFM and AM.
Righthandsection Modulatlng-slgnal display
measuringsection tor modulating
frequency.
distortion,
SINAD




Welgthlng Three HP and three lP filters provide a great
variety of weighting bandwidths and suppress unwanted
signals. CCITT and CCIR standard filters (perceived Ioud-
ness) can be inserted or retrofitted as options tor standard
SI N measurements.
Display 01 resulta (absolute or relative) The measured
modulation can be displayed as an absolute vaJue or relative
to a key-entered reference vaJue. This is very convenient if
modulation is to be determined as a funclion of modulation
frequencyor carrier frequency.

F~ 01 --'
8ICtion:ci8PIaY mcxjIMMon -- 8Id ~
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Frequency setting Setting is performed fully automat!-
cally under microprocessorcontrol; see descriptionon next
page. When a signal is applied,the FAM tunes automatically
10the input frequencywithin 3 sand displays this frequency
The high resolution (~O.25%) end the high accuracy of the
in the lefthand section with aresolution of 10Hz.
modulationdepth indication(1.5%) permit precise measure-
If automatic tuning is not desired in specific cases. the ments without needing recalibration.
frequencycan be set via the keyboard (this ia importanttor
Type of detectlon The rneasurementof the AF modul at-
instancewhen measuringselective ca/l equipment.with data
transmission and other techniques where no continuoos ing-signal amplitude can be performed either with peak-
signal is available). respondingdetectlon(most frequently employedtor measur.
ing wanted modulation)or with rms-respondingdetection(for
For sud1 specific measurements.the other automatic tunc- example tor measuring unwanted ~ulation). The CCIR
tlons can also be suppressed.AF attenuatoror AF rangecan weightlng filter option includes the prescribed quasi-peak
be held at or brought to a particularsetting. respondingdetector.
analyzers

derlves the setting of the first Iocal oscillator and perforrns the
FAM RF level adjustrnenl
Modulation-frequency I distortion measurement The Input signals above 120 MHz are converted to the range
frequency of the modulatlng slgn81 is displayed in the below 120 MHz by the second locaI oscillator of the 1.36-
righthand section of the front panel. The O.1-Hz resolution is MHz Frequency-range Extension option. The microproc-
required tor measuring frequencies of calling signals or code essor calculates the input frequency frorn the frequency of
signals tor squelch switching. the second locaI oscillator. The input frequency is displayed.

F~ 8ICIIon:
righIhn dIIP8Y n keyboan!
8ICIIon ~uency
Ior
n~~ MSDC 2

Stereo
MPX


Option FAM-B8 is avail-
able for measurlng the
dlstortlon of the modulat-
ing signal. Measurements
Meuurement 01s1-.o ~ signals ~ ModulationAnalyzer FAM
can be made at 30 fixed
trequencies trom 30 Hz to
20 kHz. The measure-
ment is automatically Initi-
Extensions (options)
ated by the microproc-
The FAM can be delivered or retrofitted with a number of
essor when the trequency
of the modulating signal options to suit different requirements:
lies within the measure- 1.36-GHzFrequency-range Extension FAM-B2
ment range. The FAM dIs- extends the frequencyrange of the FAM up to 1360 MHz.
plays either distortion in %
CCITT Weighting Filter FAM-B6
or SINAD in da.
tor weighted measurementof unwanted modulation using
Evaluation of external AF signals The AF section, com- standard perceived-loudness-characteristic
filter.
prising the weighting filter, frequency counter, detector and
CCIR Welghting Filter FAM-B7
distortionmeter.can be used tor the evaluationot an extemal tor weighted measurementof unwanted modulation using
AF signalvia a separateinput socket.The ModulationAnaly- standard perceived-ioudness-characteristic filter. The re-
zer can thus be used as an automaticAF voltmeterand as a quired quasi-peak-responding
detector is built in.
psophometer.
015T and 51NAOMeter FAM-B8
IEC-businterface The Modulation AnaJyzer has an IEC-
tor automatic measurementof modulationdistortion. includ-
bus interface so it can be controJled an external computer,
by ing external signals at 30 fixed frequenciesfrom 30 Hz to 20
eg by an R&S Process Controller. The FAM can receive
kHz.
setting and trigger instructlons and can output measured
data to the computer, meaning that it can function as both Reference Oscillator 5M5-B1
listener and talker. Thus it is suitable for use in automatic temperature-controJled.improves the frequency stability
(temperature coefficient 1x 10- 7 in the operating tempera-
measuring systems tor testing transmitters and transceivers
in deveiopment,productionand quaJitycontrol. lure range; crystal aging 5x10-8/month).


Descriptlon
The FAM is made up of the RF, IF and AF sections and the
microcomputer circuitry. The RF section contains a counter Specifications
tor measuring the frequency of the input signal, an AGC Freq~,.. ... 56 kHz k) 120 MHz
Wilh option FAM-82 , .36GHz 56 kHz 10 1360 MHz
stage and a mixer. The IF section comprises AM and FM FrequencyseIIIng . . . . . . . . aIIOm8tic I)