MODULATION ANALYZERS - Helmut Singer Elektronik

analyzersFAMModulation-frequency I distortion measurement Thefrequency of the modulatlng slgn81 is displayed in therighthand section of the front panel. The O.1-Hz resolution isrequired tor measuring frequencies of calling signals or codesignals tor squelch switching.F~ 8ICIIon:righIhn dIIP8Y n keyboan!8ICIIon Ior ~uencyn~~derlves the setting of the first Iocal oscillator and perforrns theRF level adjustrnenlInput signals above 120 MHz are converted to the rangebelow 120 MHz by the second locaI oscillator of the 1.36-MHz Frequency-range Extension option. The microprocessorcalculates the input frequency frorn the frequency ofthe second locaI oscillator. The input frequency is displayed.MSDC 2StereoMPXEvaluation of external AF signals The AF section, comprisingthe weighting filter, frequency counter, detector anddistortion meter. can be used tor the evaluation ot an extemalAF signal via a separate input socket. The Modulation Analyzercan thus be used as an automatic AF voltmeter and as apsophometer.Option FAM-B8 is availablefor measurlng thedlstortlon of the modulatingsignal. Measurementscan be made at 30 fixedtrequencies trom 30 Hz to20 kHz. The measurementis automatically Initiatedby the microprocessorwhen the trequencyof the modulating signallies within the measurementrange. The FAM dIsplayseither distortion in %or SINAD in da.IEC-bus interface The Modulation AnaJyzer has an IECbusinterface so it can be controJled by an external computer,eg by an R&S Process Controller. The FAM can receivesetting and trigger instructlons and can output measureddata to the computer, meaning that it can function as bothlistener and talker. Thus it is suitable for use in automaticmeasuring systems tor testing transmitters and transceiversin deveiopment, production and quaJity control.Meuurement 01 s1-.o ~ signals ~ Modulation Analyzer FAMExtensions (options)The F AM can be delivered or retrofitted with a number ofoptions to suit different requirements:1.36-GHz Frequency-range Extension FAM-B2extends the frequency range of the FAM up to 1360 MHz.CCITT Weighting Filter FAM-B6tor weighted measurement of unwanted modulation usingstandard perceived-loudness-characteristic filter.CCIR Welghting Filter FAM-B7tor weighted measurement of unwanted modulation usingstandard perceived-ioudness-characteristic filter. The requiredquasi-peak-responding detector is built in.015T and 51NAO Meter FAM-B8tor automatic measurement of modulation distortion. includingexternal signals at 30 fixed frequencies from 30 Hz to 20kHz.Reference Oscillator 5M5-B1temperature-controJled. improves the frequency stability(temperature coefficient 1 x 10- 7 in the operating temperalurerange; crystal aging 5x10-8/month).DescriptlonThe FAM is made up of the RF, IF and AF sections and themicrocomputer circuitry. The RF section contains a countertor measuring the frequency of the input signal, an AGCstage and a mixer. The IF section comprises AM and FMdemodulators and the AF section evaluates the demodulatedsignal. The microprocessor handles the settings, dataacquisiöon, and 1/0 operations of keyboard end display.Special features of the RF section The input frequencyrange of the FAM basic unit is 55 kHz to 120 MHz divided intotwo bands: frequencies up to 3.5 MHz are processed directlyin the IF section, those between 3.5 and 120 MHz undergo asingle frequency conversion. A frequency-range-extensionoption adds a third band above 120 MHz with double frequencyconversion.The microprocessor detects the presence of an input signalby a search process uslng level detectors in the RF and IFsections and a frequency counter. From this information itSpecificationsFreq~,.. ...Wilh option FAM-82 , .36 GHzF requency seIIIng . . . . . . . .Display R-*IIon. f < 1(Xk) , Wfz ..f ~ f (Xk) Wfz ..F~_andc*;lt..R8'-"ce ~1IaQ . . . . . . . .Cly8IaI ~ . . . . .T ~Iure coeIIIcient ...56 kHz k) 120 MHz56 kHz 10 1360 MHzaIIOm8tic I) « ~8c1gits10Hzor1Hz100 Hz« 10 Hz:I: 1 cIgiI + errrx ~ treq.lI88d ~ SM$-81