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ST- 8O8O runer /AM FM stereo H i g hS e n s i t i v i t F y ront-End (10.8d8f) with 2-StageRF dM Amplifiea r n d4 - G a n g eF Tuning Capacitor Variable The adoption of two low-noise4-poledualgate junction FETs and linear4ganged FM variabletuning capacitorin the 2-stageRF amplifierstage is largelyresponsiblefor the very high sensitivityin the frontend. Usablesensitivityis 10.8dBf(or 1.9pVac'58)at 300a antenna input cording to IHF impedance,while the 50dB quieting sen'58)at sitivity (stereo)is 34.3dBf(or 28.4yVIHF 3004. With this kind of sensitivity,together with the greatly reducedinterferencesignal levels,even very remote FM stations are receivedwith great clarity and fidelity. Of special importanceis the suppressionof the interferencecaused by RF intermodu- We ProposeEveryFM TunerMustHave This Kindof WaveformFidelity With the remarkableadvancein audio technologyachievedwithin recent years,and the ceaselessstrivingof an elite team of engineersdevotedto the task of producing perfect sound reproductionequipment, Technics has succeededin achievingvery high standardsin its audio equipment,as can be seen in the case of the ST€080 stereo tuner.This high standardwill inevitably becomethe norm in future years,but that is hardly welcome news for audio enthusiasts looking for the best their money can by now. The ultimateaim in any top grade stereo tuner is the perfect reproductionof the originalwaveformof the qadiosignals transmitted from the broadcastingstation.This is certainlyno easy task, since, besidesother things, this involvesthe complete banishment of all interferenceand noise signals and the ability to maintainstereo separationat exactly the same levelas in the originalsignals. The waveformof the signals comprisingany musical expressionis usuallyvery complex, and cannot be used effectivelyto point out the differencesbetweenoriginaland reproducedsignals.In normal analysis,the tuner's ability to reproducethese signals is shown by using simple squarewave and tone burst signals. The resultsshown here illustratethe marked differencesbetweenthe ST8080 (in which the ultimatedesign priority has been placed upon waveformfidelity)and a conventionaltuner (conspicuousfor the lack of emphasison waveform). PhotographA. The results shown in this photographhighlightthe differencein responseto a composite signal of a 50Hz squarewave signal plus lkHz sine wave signal.The very steep "sag" in the square wave output signal from the conventional tuner is indicativeof the poor amplification phase characteristicsin the low frequency region (which introducesdistortion into the signal),while the depressedsections at the start of the lkHz sine waves signify a very small dynamic rangeat lower frequencies. PhotographB. SkHzand 15kHzsine waves are modulatedand demodulatedindependently, but are shown here (upperhalf of photograph)on the same time axis in order to revealany change in time relationbetween the waves.The outout of the ST8080 shows no time change whatsoever,while the SkHz and 1SkHzsignals passedthrough the conventionaltuner havearrivedat the output at differenttimes. lf these 2 signalsare then combined(lowerhalf of photograph)the loss of waveformfidelity in the conventionaltuner is even more evident. lation,and the consequentimprovementin selectrvity in the more crowdedsectronsof the FM band.The RF lM interference rejectioncurvesare shown here in graph form. Naturally, the higherthe values(in dB) the better,but such valuesare very difficult to obtainwithoutsacrificingsensitivityin receptionof distantstations.Albeit,as can be seen in the graph,Technics has succeededin attaininga very high standardindeed,and this withoutcompromisingsensitivityat all. signalcan still be singledout with a high degreeof clarity.Thesefiltersalso assisi in maintainingexcellentstereoseparation. Hereagainis ampleevidenceof the very carefulattentionthat Technicspaysto the performance of the audio equipmentit designs,not only in terms of audio requirements, but also in terms of per- S u p e rF l a t F r e q u e n c y Responsef rom 20HzIo 1 8 k H z( + 0 . 2 d 8 , - 0 . 8 d 8 ) FM Selectivity Needlessto say, waveformfidelity would be impossibleto aitain in a tuner sufferingfrom phase inversionand poor frequencyresponse. In the ST€080,the 19kHzpilot signal, reouiredfor stereodemodulationin the MPX curcuit,is cut out with razorsharpprecision by the pilot cancelcircuit(a Technicsinventionnow copiedby many other Besidesimprovingf requency manufacturers). response,it also reducesdistortion,and escapesthe problemof phase inversion cl o 0) $ c o N e w D e v e l o p m e n ti n s Local O s c i l l a t oar n d M i x e rS t a g e FurtherlrnproveStability and S/N Ratio The greateroverallstability of the ST€080 tuner is also due to the improvedstabilityof the localoscillatorand mixercircuitswhich incorporatespecial low-noisetransistors,and a recentlydevelopedaluminumcore oscillator coil.And circuitsectionsDroneto the effects of changinghumidity,etc. havebeenfurther stabilizedby the use of specialpoint-to-point wirrngtechniques. The use of soecial low-noisetransistors designedto eliminatenoise in both high and low frequencyregions,and the extremely strict selectionof circuitcomponents,have greatlyattributedto the very high S/N ratio, and the noticeablelack of frequencydrift. Specialcare has been taken to separate oscillator'shot side from the foil on the orintedcircuitboard.anotherinnovation resultingin driftjree performance.- AdvancedType Flat Group D e l a yF i l t e r sS o l v et h e C o n f l i c t i n gD e m a n df o r H i g hS e l e c t i v i tay n d L o w D i s t o r t i o ni n l F S t a g e A selectivityrating as high as BsdB,and a distortionratioas low as 0.15%(100% modulation,MONO)in the ST8080 has been accomplishedby some very cleverelectronic engineering. The four flat groupdelayfilters (one narrowband type, and three wide types) feature4-resonatortype ceramic filters of very high selectivitycharacteristics.In addition, the amplificationstage consists of 3-stage and 2-stagedifferentialamplifiers(in twoseparate lCs) connectedto a quadraturedetector. At +400kH2,a very impressivealternate channelselectivityof 85dB has been obtained. And evenat +200kH2,selectivityis still in excess of 10d8, which meansthat no matter how crowdedthe band mav be. the desired formanceas communications equipment.No matter how low harmonicdisto,.tionmay be suppressed, it will havelittlesignificanceif the systemis still subjectto other forms of interference. Only when all performance requirements are fully met,canthe equipment be honestlybe consideredas a genuineFM stereotuner. o c TotalHarmonicDistortion o 0) E b bur'ri*i rr*iu"n"y'dsrr,rit ' lnterlerencesignalirequency: 400H2 Interference signalmodulation : 1000,6 Interference/desired signaloutputratio: -30d8 -600 -400 -200 0 +200 +400 +600 6 a s c t Frequency devialion Modulation frequency{Hz) PLL MPX DecoderBbck Diagram Pilot B.P.F. sTa080 Effect of Pilot Cancel Circuil O u t p u ts p e c t r u mw h e n f . m o d . 1 0 k H zi n p u t i s a p plied. Letl: ST8080-note almost completeabsence Conventional o f 1 9 k H za n d o t h e ru n w a n t e dc o m p o n e n t sR . ight C o n v e n t i o n al ul n e r w i l h o u tp i l o t c a n c e lc i r c u i t . first-stagedifferentialSEPPoutput for audio frequencyamplification,and is operatedby a stabilizedpower supply. Besidesthe variable leveloutout control.the STB0B0also features a separateoutput for tape decks.The level volume control is the precisionadjustedlow gang errortype.The fixed output terminals (for recording)include a specialtype of lowpass filter of excellentphase delay characteristics,and which suppressescarrier leakto less than -70d8. OscilloscopePatternol 20 Hz-20kHzSweepEnvelope IndicatesTuner'sFrequencyResponse. B u i l t - i nR E CL e v e lO s c i l l a t o r for LevelSettingAccuracy This oscillatorgeneratesa 440H2sine wave siqnal whose levelcorrespondsto an FM radiosignalof 50% modulation.This enables recordingenthusiaststo adjust recording levelsto a very high degreeof precision. Left: ST€080 with Pilol Canceler Right: Conventional Tuner with Low Pass Filter associatedwith low pass filters (which also inavoidably cut off some of the high frequencyportionsof actual FM programs). Excellentlinearityis also obtained,the responsecurvebeingincrediblyflat (+0.2d8 -0.BdB)all the way trom 20Hz to .18kHz. gainedby Togetherwith the rmprovements the flat groupdelayfiltersin the lF stage,an extremelyhigh degreeof f idelityin waveform the Furthermore, has beenaccomplished. 3BkHzsubcarriersignal has also been cancelledby a similarcircuit.reducingthe possibilityof interference from this sourceto zero. SuperbStereoSeparation ( 4 5 d 8a t l k H z ) D u et o N e w P L Ll C i n M P XC i r c u i t Although the PLL (PhaseLocked Loop) systemis now quite common in the MPX circuit(wherethe left and right stereosignals are retrievedfrom the transmitted "multiplex"signal), the ST€080has improved upon this systemby accommodatingit in a newly developedlC (AN363).The advantages includegreaterstabilityand reliabilityunder varyingexternalconditions,decreased distortionespeciallyin the high frequency region,and higherstereoseparation. The improvementin waveformtransmissionis qurtemarked(seephotographAand B), not only becauseof the greatly reducedhigher harmonics,but also becauseof the reductionof unwantedcomponentscausedby beating. This lC employsa voltagecontrolled oscillatorto generatea76kHz signal,which is then dividedinto 3BkHz,and 19kHzsignals. .19kHz perfectly This signalis synchronized with the pilot signal,passedout of the lC via pin no.12,and undergoeswaveformshaping into a pure 1gkHzsignal,which is then mixedwith the compositesignalat the input of the MPX circuit,resultingin the cancellationof the unwantedpilot signal.This furthereliminatesthe occurrenceof oroblems in the succeedingnonlinearcircuits. Low NoiseAF Amp Stage EquivalentCircuit Outpul Level & StereoChannel Separation OUT PUT L o w - N o i s eA m p l i fi c a t i o n l C i n A F S ta g e The thoroughness of Technicspursuitfor waveformfidelity is further emphasizedby the qualityof the circuitryemployedin the AF stage.The lC adopted here includesa High GradeSignal Strength Meter for Greater Precisionand Versatility Linkedto the quadraturedetectorcircuit, this extremelylinearsignalmeter(flat right up to 65dBf)is fully qualified to measuresignal strengthsto very high levels.This will prove very usefulin findingoptimumantenna positionand directionfor weak and strong FM stationsalike. Signal Strength Meter lndication vs. lnput Signal Level Two-WayMuting With mutingcircuitryin the reedrelayof the output stage,and in the quadraiuredetector lC,2-waymutingis providedto suppress inter-station and tuning noiseto a high oegree. MPX Hi-Blendlor Noise-FreeStereo Receptionof Distant Stations The multiplexhi-blendswitch bettersS/N ratios in receptionof weakerand more distant FM stations.The ST80B0also featuresmultipathmeasuringterminalsto which an oscilloscopemay be connected. Optimumantennapositionand directioncan thus be determinedwith great accuracyin situationstroubledby multipathinterference. Also High Quality AM Reception Nor has there beenany skimpingin design considerations for AM reception.Incorporatinga highQ ferritebar antenna,an lC developedspecificallyfor AM, and the very high selectivityof the ceramicfiltersin the lF high receptionstandards stage,exceptronally have been achieved. ST-8080Block Diagram e-+I*' lA*|*,-lg* l-l-l MULTI PATH 4ch MPX OUT STEREO EYE +F----**-@tour *- t' tut . [#{.ll , c a ll sQ,$ Jlfo Low Passfilter - !-FM , ;l Powersupply lrr,",.",,, lF circuit REC levelche oscillator RearPanelFacilities Technical 4s5oo) Specificationsrorr.r 1. FM antennaterminalsg5 a, 300 O) 2. Groundterminal 3. AM antennaterminal 4. AM fenite bar antenna 5. Outputterminals(variable) 6. Outputterminals(fixed) 7. 4-channelMPX output & FM multipath outputs FM TUNERSECTION F r e q u e n c yr a n g e 8 8 - 1 0 8 M H z S e n s i t i v i t (y+ 4 0 k H z d e v i a t i o n ) S/N30dB 1.8 pV (300o), 0.9 ;rV (75 O) s/N 26 dB 1.6 pV (300o), 0.8 uV (75 o) 1.4 pV (300o), S/N20 dB 0.7 pV (75 O) I H F u s a b l es e n s i t i v i t y 1 0 . 8d B f ( 1 . 9 p V , 300 o tHF '58) S / N 5 0 d B q u i e t i n gs e n s i t i v i t y 1 3 . 6d B f MONO (2.6 pV, 300 o IHF '58) STEREO 34.3dBf (28.4pV, 300 o rHF'58) T o t a lh a r m o n i cd i s t o r t i o n MONO 0 . 1 5 %( 1 k H z ) STEREO 0.3oh(1 kHzl S/N (40 kHz deviation) 7 0 d B ( 7 5d B , r H F ) MONO Frequencyresponse Variable 2OHz-18 kHz, Fixied (DrN) Alternate channel selectivity Capture ratio lmage rejection at 98 MHz l F r e . i e c t i o na t 98 MHz +0.2dB, -0.8 dB 20 Hz-'|.5 kHz, +0.2dB, -0.8 dB 2OHz-18 k4z, + 1 . 5d B 85 dB 1 . 0d B 85 dB 1 0 0d B S p u r i o u sr e s p o n s er e j e c t i o n at 98 MHz 95 dB AM suppression 55dB S t e r e os e p a r a t i o n 4 5 d B ( 1 k H z ) , 3 5 d B ( 1 0k H z ) Carrier leak Variable Designedto the same high standardsas the ST8080,the SU€080servesas the perfect mate for this tuner, featuringa wide rangeof very advancedelectronic systems,and a capacityfor very diversifiedapplicationsin any high gradestereocomponentsystem. Fixed - 6 0 d B ( 1 9k H z ) , - 6 5 d B ( 1 9k H z ,t H F ) - 6 5 d B ( 1 9k H z ) , - 7 0 d B ( 1 9k H z , 3 8k H z , l H F ) 1 . 2p V L i m i t i n gp o i n t Bandwidth 2 5 0k H z lF amplilier FM demodulator 820 kHz Antennaterminals 300 12.75 O AM TUNERSECTION F r e q u e n c yr a n g e 5 2 5 - 1 6 0 5k H z Sensitivity ( S / N= 2 0 d 8 ) 30 ttV 25 dB Selectivity lmage rejectionat 45dB 1 , 0 0 0k H z lF rejectionat '|,000kHz 40 dB GENERAL O u t p u tv o l t a g e 0-1.4V Variable 0 . 6v Fixed 14W P o w e rc o n s u m p t i o n V 110/120/220/240 P o w e rs u p p l y 450 x 140x367 mm Dimensions (17-23/32"x5-1/2" x (wxHxD) 14-7/16") 8 . 4 k g ( 1 8 . 5l b s . ) Weight @Technics S p e c i f i c a t i o n ss u b j e c t t o c h a n g e w i t h o u t n o t i c e . P r i n t e d i n J a p a n So7DO5O20E