Technology of Q 2500 colour TV set

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Technology of Q 2500 colour TV set3 Receiver components3.1 HF/IF unitFour receive components can be used in deviceswith Q 2500 chassis. One is the terrestrialtuner, or HF/IF component, which processesfrequencies from 47 MHz to 860 MHz.This hyperband tuner is located on the basicboard.Second is the single SAT or dual SAT receiverfor the first IF from 950 MHz to 2150 MHz.This is partly a standard feature or can beretrofitted for certain sets.In addition, for full IP sets a PIP-HF/IF unit forthe reception of terrestrial signals is incorporatedinto the hyperband range. In this case,however, the audio band is dispensed with, aspicture for picture only video signals are required.This is also built into the basic board.With this equipment the set is able to processall television signals, irrespective of whetherthey are received by terrestrial antennae orvia cable units, and even when derived fromparabolic antennae.3.1.1 HF/IF componentsA HF/IF combination is also used. All functionsfor current European television standardsare located in one housing, with twoprovisos. The IF consists of only one pictureIF. The audio demodulation takes place in theaudio IC on the signal board. From the IFcomponent only the sound IF is supplied asbroadband.This means that the ceramic transducer andan expensive sound/IF switch are not required.Secondly, for lower price models notdestined for export HF-IF, designed only forPAL and SECAM BG, is used. In this case,the change-over to SECAM L and NTSC andthe components necessary for this are notrequired.This means the two designs are hardware andsoftware compatible.The following block circuit diagram shows themulti-standard design. Some of the componentsare not fitted to the BG version.As in earlier models, the electronics is housedin an HF proof folding housing.Document Q 2500 44 © Loewe ProCollege
Technology of Q 2500 colour TV setIF-AGCAntennen Splitter45 MHzhigh pass27 MHztrapAnt inAnt out power splitterMASV5TunerM, N, BG, I, DK, L, L1V9IFHigh Band ChighoscIFon/offMixerrejection Mid Band Cmidoscon/offMixerLow Band AlowoscMixerBSV9CNORBAV5P4 P5LOBSPMNBLIL1PNAFCV9 TAGC V33 SCL SDA IDCMNBLML1ZFSyst.: M, N, BG, I, DK, L, L134,4 40,412 M L132,38 33,412AFCDetectorCVBSM,NAFSSIFon/offPLL0123770-150mVZF-inpos./neg.switchCSAGC PNSIFM o. L1AGCSIFQSS - IntercarrierMixerAmpl.SIFAM Demod.I,DK,L BG,L105....10mVVIFAmplifierVCOFPLLTWDTunerTuner VIFM,N BG,I,DK,L,L1AGC AGCAGCd = 25 dBAEL1TOPCblFM-PLL-DemodulatorVoltageRef.TDA 9818Video DemodulatorAmplifierTunerAFC4,5 5,5 5,74C AF+5V21Cv AGCT PLLMixer Osc ICCCVSDocument Q 2500 45 © Loewe ProCollege
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