森海塞尔无线话筒频率测试系统UserManualproUS.docx
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森海塞尔无线话筒频率测试系统UserManualproUS
“SIFM”
Instructionsfortherapidcalculationofintermodulation-free
radiofrequenciesforwirelessmicrophonesystems
SennheiserIntermodulationandFrequencyManagement
SIFM:
SennheiserIntermodulationandFrequencyManagement
NoLiability
Thisversionisintendedforprofessionalusersabletointerprettheinput
ofthetechnicalparametersinapertinentway.
Whencalculatingfrequencyconfigurations,usethedefaultvaluesasastartingpoint.Theseofferthehighestinsensitivitytointermodulationinterference.Themanufacturersandtheindividualusersrequirefrequencyconfigurationswhichensurereliableresultsunderawiderangeofdifferentoperatingconditions.Sennheisercanacceptnoliabilityfortheoperationalsafetyofmulti-channelsystemswhosetransmissionfrequencieshavebeencalculatedonthebasisofthisprogramwithoutourapproval.
Introduction
Interferenceduetointermodulationgenerallyoccurswhenatleasttwotransmittersclosetothereceivingantennaproduceverystrongsignalsinthereceiver.Thetwosignalsformintermodulationproductsatnon-linearities,suchastransistorsorothersemiconductorsinthereceiver（e.g.inthemixer）.Unwantedsignalsareproducedwhichmayinterferewiththewantedfrequenciesofthesystem.
Intermodulationsignalsarealsoproducedwhentwoormoretransmittersoperateincloseproximitytooneanother.Inthis
case,thetransmitternotonlytransmitsitsownsignalbutalsoreceivesthesignalsfromtheothertransmitters.Fromboth
signals,thetransmittergeneratesandre-transmitsmixtureproductswhichcaninterferewiththewantedfrequencies.
Forreasonsofoperationalreliability,awirelessUHFtransmissionsystemhasalimitedswitchingbandwidth（e.g.36MHz）.Thisswitchingbandwidthisdeterminedbyinputfiltersinthereceiver.Intermodulationproductswithinthisrangecaninterferewiththeselectedreceivingfrequencyorwiththewholesystemandcanmakethesysteminoperable.ChoppingnoiseorhissinginthebackgroundisanacousticindicationoffrequenciesinterferedwithbyIMproducts.Inprinciple,receivingandtransmittingfrequenciesformulti-channelsystemsareplannedasfollows:
Inanexamplesystemhavingtwocarrierfrequenciesf1=800MHzandf2=801MHz,theresultingintermodulationproducts
withintheswitchingbandwidthofthereceiveraretobedetermined.
Thereareharmonicsofthefundamentalfrequenciesandsumanddifferencefrequencies.Theharmonicsdonotinterfere
sincetheyarefaroutsidethereceivingrangeandwillbeeffectivelyrejectedbytheinputfiltersinthereceiver:
2f1=2x800MHz=1600MHz
2f2=2x801MHz=1602MHz
3f1=3x800MHz=2400MHz
3f2=3x801MHz=2403MHz
Simplesumanddifferencefrequenciescanalsobeignoredastheyarealsofaroutsidethereceivingrangeandwillbe
effectivelyrejectedbytheinputfiltersinthereceiver:
f1+f2=800MHz+801MHz=1601MHzf2–f1=801MHz–800MHz=1MHz
IM3=2f1–f2=1600–801=799MHz
IM3=2f2–f1=1602–800=802MHz
IM5=3f1–2f2=2400–1602=798MHz
IM5=3f2–2f1=2403–1600=803MHz
IM7=4f1–3f2=3200–2403=797MHz
IM7=4f2–3f1=3204–2400=804MHz
AmultitudeofIMproductsareproducedinmulti-channelsystems.Properfrequencyselectionthereforerequirescomputer-aidedplanningthatcanbedoneusing“SIFM”.Inespeciallycriticalcases,Sennheiser’sServiceDepartmentoryourSennheiseragentwillbepleasedtocarryoutthisplanning.
Attention!
Sennheisersystemsarenormallysuppliedwithintermodulation-freefrequencysets.However,inmostcountriesalicenseisrequiredfortheiruse.PleasecontactyourlocalSennheiseragentand/orthelicensingauthorityinyourcountryforinformation.Theexceptionisthefrequencyband863MHzto865MHzwhichislicense-freeinmostofEurope（ETSIsignatorycountries）.
However,itisnotonlythenumberoffrequencycalculations,butalsothedemandontheperformanceoftheradio
microphoneequipmentusedwhichdrasticallyincreaseswithadditionalchannels.
Receiverintermodulationoccurswhentransmittersoperatetooclosetothereceivingantennas（<4m）.
Transmitterintermodulationoccurswhentwoormoretransmittersoperateincloseproximitytooneanother
（<30cm）.
Thestrengthoftheintermodulationsignalsincreaseswithdecreasingdistances.
Largesystemsrequirealargebandwidth
（MHz）
80
70
60
50
40
30
20
10
0
1012141618202224
（Channels）
Thebandwidthrequiredincreasesdisproportionatelywiththenumberofchannels.ThenumberofpossibleIMproductsrunsintothousands.
Morethan16channelswithintheswitchingbandwidth（24MHz–36MHz）arerarelyadvisable.
选择View菜单中的“系统设置
”
Startpage
Fromthe“View”menu,
select“SystemDesigner”.
点击下一步
Click“Next”.
点击“转换”转换系统，或者点击“下一步”确认选择系统。
Changethesysteminusebyclicking“Change”
or
Confirmtheselectedsystembyclicking“Next”.
Clicking“Change”opensthe“SelectReceiverSystem”window.
Selecttheequipmentused.
Adapttheparameters.
调整参数
选择“设备使用”
点击“转换”打开“选择接受系统”窗口
Onlychangetheparameterswhentherequirednumberofchannelscannotbeobtained.
ReducingthedistancesresultsinmorechannelsbutalsoincreasesthelikelihoodofIMinterference.
减少距离获得更多频道，但是也可能会增加对IM的干扰。
仅在不能获取所需要的频道号码时再更改参数
一步一步的方法使频道号码和操作安全之间更好的结合。
Confirmbyclicking“OK”andlettheprogramcalculate.
Sequenceduringthesearch:
With3transmitters:
Reducetheintermodulationdistance（3TxIM3）to0（removethetick）.
With2transmitters:
Reducetheintermodulationdistance（2TxIM3）to
100kHzmin.
Reducethechannelspacingto300kHzmin.Withevolutionwirelessequipment:
375kHzmin.
Reducethe
distancestoadjacentIMproductsinstepsof25kHz.
Astepbystepapproachyieldsagoodcompromisebetweenthenumberofchannelsandoperationalsafety.
3个信号传送器：
减少互调距离（3TxIM3）到0（去除滴答声）
进化无线设备：
375khz/分钟
减少频道间隔到300khz/分钟
2个信号传送器：
减少互调距离（2TxIM3）到100khz/分钟）
序列中搜索
点击“OK”确认程序计算
减少距离让IM接近25KHZ.
Selecttheoperatingmode.
选择操作模式
点击“开始”
进入宽带
Enterthebandwidth.
Click“Start”.
几秒钟后会计算出频道号码（20）
Thenumberofcalculatedchannels（20）isdisplayedafterafewseconds.
Theresidualtimerequiredtocalculateallpossibilities
isalsodisplayed（5days）.Thiscouldresultin1or2
morefrequencies.
Afterclicking“Abort”,theresultisdisplayed.
点击：
“Abort”后，会显示结果。
剩下的时间会计算出所有可能的频道号码显示（5天），这就导致会多1到2个频率。
Click“Full”foragraphicdisplayoftheresult.
IMproducts
Radiomicrophonefrequencies
Bandlimits
频段范围
频段范围
IM产品
无线麦克风频率
点击“Full”显示图形结果。
打印结果：
在“File”菜单中选择“创建打印版本”
Toprinttheresult:
Fromthe“File”menu,
select“CreatePrintVersion”.
The“CreateRTFFile”
windowopens.
（ThisisinGerman）
Enterafilenamein
the“Dateiname”field.
Clicking“Speichern”automaticallyopensawordprocessingprogramforprinting.
点击“Speichern”自动打开一个文字处理程序进行打印。
进入文件名类型
此语言为德语
在“创建RTF文件”窗口打开
结果打印预览
Printviewoftheresult
The
End
Done!
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