标签: hamradio

HamRadioMelexisRFTransmitterandAntennaDesignHintsApplicationsNoteRFTransmitterandAntennaDesignHintsThisapplicationnotecoverstheTH7107,TH71071,TH71072,TH7108,TH71081,TH72011,TH72031,TH7204SingleFrequencyTransmitters.Thesetransmittershavedifferentfeaturesandcoverdifferentbandsbuttheyallhavecommonfeatures,whichmakethemveryeasytousefordifferentapplications.Featurescommontoalltransmitters:Themostcommonfeatureofallthetransmittersisthattheoutputfrequencyis32timesthereferencefrequency.Inmostcases,thereferencewillbeaquartzcrystal,butitcouldalsobeanexternalsourceconnectedtotheRO1pin.ThecapacitancelookingintotheRO1pinisapproximately15pF.Thereforethecrystalshouldbespecifiedtohavealoadcapacitanceof15pFatthedesiredoutputfrequencydivid……

HamradioIntroductiontoAntennaMeasurementTheoryAntennaMeasurementTheoryIntroductiontoAntennaMeasurement1.BasicConcepts1.1ELECTROMAGNETICWAVESTheradiationfieldfromatransmittingantennaischaracterizedbythecomplexPoyntingvectorExH*inwhichEistheelectricfieldandHisthemagneticfield.ClosetotheantennathePoyntingvectorisimaginary(reactive)and(E,H)decaymorerapidlythan1/r,whilefurtherawayitisreal(radiating)and(E,H)decayas1/r.Thesetwotypesoffieldsdominateindifferentregionsinspacearoundtheantenna.BasedonthischaracterizationofthePoyntingvector,wecanidentifythreemajorregions(Figure1).Figure1:RadiatingRegions1.1.1.ReactiveFieldThisregionisthespaceimmediatelysurroundingtheantenna.Theextentofthisregionis0