AmateurRadioTechnicianClassElement2Course…-4724：业余无线电技师班2元课程……

《AmateurRadioTechnicianClassElement2Course…-4724：业余无线电技师班2元课程……》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、TechnicianLicensingClassWeakSignalPropagationSection10WeakSignalPropagationT5C7Radiowavesisausualnameforelectromagneticwavesthattravelthroughspace.ElectromagneticwavesareRADIOWAVESWeakSignalPropagationT3C10Thedistanceatwhichradiosignalsbetweentwopointsareeffectivelyblockedbythecurvat

2、ureoftheEarthistheradiohorizon.VHF&UHFradiosignalswillgenerallytravel“lineofsight.”VHF&UHFradiosignalsareblockedbythecurvatureoftheEarth.WeakSignalPropagationT3C11VHFandUHFradiosignalsusuallytravelsomewhatfartherthanthevisuallineofsightdistancebetweentwostationsbecausetheEarthseemsle

3、sscurvedtoradiowavesthantolight.Knife-EdgePropagationT3C5Theterm"knife-edge"propagationreferstosignalsthatarepartiallyrefractedaroundsolidobjectsexhibitingsharpedges.WeakSignalPropagationT3C6Troposphericscatterisresponsibleforallowingover-the-horizonVHFandUHFcommunicationstorangesofa

4、pproximately300milesonaregularbasis.T3C8Temperatureinversionsintheatmospherecauses"troposphericducting".TroposphericDuctingWeakSignalPropagationT3C3AcharacteristicofVHFsignalsreceivedviaauroralreflectionisthatthesignalsexhibitrapidfluctuationsofstrengthandoftensounddistorted.Incoming

5、signalsfromadistantstationheardhundredsofmilesawaywillsoundflutteryanddistortedbyauroralbounceWeakSignalPropagationT3C7The6meterbandisbestsuitedtocommunicatingviameteorscatter.LeonidsandGeminidsmeteorshowersprovidetheseconditionsBouncesignalsoffmeteortailWeakSignalPropagationT3A11The

6、ionosphereisthepartoftheatmospherethatenablesthepropagationofradiosignalsaroundtheworld.T3C9Duringdaylighthoursisgenerallythebesttimeforlong-distance10meterbandpropagation.WeakSignalPropagationT3C2WhenVHFsignalsarebeingreceivedfromlongdistancesthesesignalsarebeingrefractedfromasporad

7、icElayer.Sporadic-ErefractionsoffionizedpatchesoftheionosphericE-layerarecommoninsummeron6-meters.WeakSignalPropagationT3A9Acommoneffectof"skip"reflectionsbetweentheEarthandtheionosphereisthepolarizationoftheoriginalsignalbecomesrandomized.Skiphappenswhensignalsrefractandreflectoffth

8、eionosphere.