全省种粮大户情况汇总表titl

《全省种粮大户情况汇总表titl》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。

1、ChelmsfordAmateurRadioSocietyAdvancedCourseTransmittersPart-2-Mixers&ModulationMixersinTransmittersNeedtorecallandexpandIntermediatecourseonmixersandmodulationinTransmitters.IngeneralVFOs,CrystalOscillatorsandSynthesisersdonotdirectlygeneratethefinalRFOutputfrequency.Mixersareusedtocombinet

2、woormorefrequencysourcesaspartofthemodulationandup-conversionscheme.Needtounderstandthatspuriousoutputscanalsooccur,aswellasdeviationissuesonFM.MixersTwofrequenciescanbecombinedinamixercircuitResultisthecreationofsumanddifferencefrequenciesMixer10MHz+1MHz=11MHzand10MHz–1MHz=9MHz10MHz~1MHz~NO

3、TE:Overdrivingamixer,underdrivingtheLOport,orpoorsuppressionofharmonicscanresultinotherunwantedspuriousmixerproducts.IfPSUisolationispoor,mainshumsidebandscanalsobeinadvertentlyaddedMixerasaModulatorMixermaybeusedasanAMmodulatorAMhascarrierandtwosidebandsMostpowerisinthecarriersignalExcessiv

4、eaudiocausesover-modulationMixer1.401MHzUppersideband1.399MHzLowersideband1.400MHzCarrier1.4MHz~1kHz~DCoffsetunbalancesmixerandcausescarriercomponent.DCoffsetBalancedMixersABalancedMixerisusedtocreateSSBasitwillnullifythecarriercomponenttoleavethetwosidebandsRFIsappliedtocentretapswhichresul

5、tsinnullnetcarrierAMcanbegeneratedbydeliberatelyunbalancingitAudioInputDoubleSidebandOutputRFCarrierInputAM&SSBBandwidthSSBhasanumberofadvantagesNocarrier,sopowerisnotwastedHalfthebandwidthofAMNoRFpowerwithoutmodulatingaudioSmallerPSULessheat+300HzCarrierLowerSidebandUpperSideband-3kHz-300Hz

6、+3kHzSSB:2.7kHzBWAM:6kHzBWCarrierandUnwantedSidebandissuppressedcomparedtonormalAM,reducingbandwidthFMModulatorColpittsOscillatorwithFrequencyModulationbyVaricapDiodeL1andC1setnominalfrequency,whichisvariedbyCDFMBandwidthismorecomplexassidebandsextendwiderthanAMC3470pFC4680pFC1150pFR2330R110

7、0kTR1+9VC2220pFOutputVaricapDiodeC522pFL110uHL2RFBlockAudioInDCBlockCDDCBiasTransmitterUpConversionSSBgenerationandothermodulationisperformedatloworintermediatefrequenciestoeasedesign,filteringetcThismustbeup-convertedtofinalRFfrequencybyanothermix