nominal nominal electrical engineering audio engineering refers approximate designed electrical circuit device term applied number different fields encountered respect nominal value characteristic cable form transmission line nominal value input output image port network especially network intended use transmission line filters nominal value input radio frequency antenna actual vary considerably nominal figure changes frequency case cables transmission lines variation length cable properly terminated usual practice speak nominal constant resistance frequency zero component despite far case depending field application nominal referring specific point frequency response circuit consideration low frequency mid band point specific applications discussed sections applications number values nominal recognised standard nominal component circuit assigned standard values regardless measured exactly corresponds item assigned nearest standard value nominal started specified early days telecommunications available available expensive consequently necessary achieve maximum power transfer cable receiving end order lengths cables installed apparent reflections transmission line severely limit distance transmit matching equipment characteristic cable reduces reflections eliminated altogether match perfect power transfer end cables equipment started specified standard nominal earliest widespread standard originally said choice figure way local exchange characteristic local telephone cable old style connect exchange twisted pair leg pair connected relay detect signalling line hook etc end connected supply voltage second connected ground telephone exchange relay terminating line telephone networks generally twisted pair cable audio frequencies especially restricted telephone band frequencies far constant possible manufacture kind cable characteristic value specific frequency quoted nominal frequency characteristic rapidly rises dominated resistance cable frequency falls audio band tens hand high frequency region characteristic constant reason response explained primary line local area networks commonly use similar kind twisted pair cable screened manufactured necessary similar telephone cable nominal rated data higher frequency band characteristic substantially flat line nominal led port networks filters designed matching nominal nominal low pass symmetrical filter sections generally image filter sections defined limit filter image frequency approaches zero given formula defined constant filter seen expression purely filter transformed band pass filter equal nominal resonance low frequency nominal filters generally nominal circuit cable filter working universal standard local presentation customer premises exchange long distance transmission trunk lines exchanges standard nominal usually lower field radio frequency microwave engineering far away common transmission line standard cable line arose nominal world war work radar compromise requirements standard work wartime joint requirement minimum loss loss cable given formula metre loop resistance metre characteristic making diameter inner conductor larger decrease decreasing decreases loss hand depends ratio outer inner decrease increasing inner conductor diameter increasing loss specific value loss minimum turns air corresponds characteristic produced war rigid air pipe remained case time second requirement maximum power handling important requirement radar condition minimum loss power handling usually limited breakdown voltage similar compromise terms ratio conductor making inner conductor large results thin breaks lower voltage hand making inner conductor small results higher electric field strength near inner conductor field lines closer smaller reduces breakdown voltage ideal ratio maximum power handling turns corresponds characteristic air geometric mean figures formula rounding convenient number wartime production period tended use standard pipe sizes outer conductor standard sizes inner conductor resulted nearly matching critical requirement voice frequencies cable started available truly need arose matching circuits interface new cables legacy equipment strange matching network cable highly desirable power handling capabilities commercial production large size inner conductor makes difficult manufacture case cable cable nominal use early period telecommunications low loss characteristic according chosen nominal corresponded standard wire size inner conductor video cables near universal standard nominal radio antennae widespread idea cable nominal arose connection input antennae myth true common antennae easily matched cables nominal quarter free space half free space half folded commonly seen television antennae hand times straight line folded commonly taken having nominal respectively installed antenna feed point varies quoted value depending installation height ground electrical properties surrounding earth cable quality measure cable manufacturing installation quality closely characteristic nominal length changes caused variations geometry cable length turn caused faulty manufacturing process faulty installation observing limits bend unfortunately easy non destructive method directly measuring cable length indicated indirectly measuring reflections return loss return loss reveal cable design return loss having purely characteristic technique carefully adjust cable termination obtain close match possible measure variation return loss frequency minimum return loss measured called structural return loss measure cables adherence nominal direct correspondence errors generator effect close measurement carried band frequencies significant reason equally spaced errors introduced manufacturing process cancel invisible reduced certain frequencies quarter wave action audio systems audio systems professional domestic components low connected high poorly defined nominal usually assigned kind connection exact little difference performance long times larger common scheme audio electronic units general form larger equipment connected short distance audio needs transmitted large distances case broadcast engineering considerations matching reflections telecommunications standard normally mean nominal standards encountered sending receiving advantages nominal transmission line transmission chain value nominal audio system important connected circuit capable dealing appropriate range assigning nominal convenient way quickly determining likely dealt separate sections kept relatively low compared audio components required audio power transmitted dangerously high common nominal common reserved high frequency compression drivers high frequency end audio spectrum usually require power reproduce constant frequencies typical rise increasing frequency value shown reaches point mechanical resonance following resonance falls minimum begins rise speakers usually designed operate frequencies resonance reason usual practice define nominal minimum round nearest standard value ratio peak frequency nominal perfectly possible low frequency actually lower nominal given audio capable driving low frequency capable driving nominal problem solved use crossover filters supplied days vacuum tubes nominal valve require output match high output voltage output lower commonly tapped allow matching output multiple setup example parallel advent solid state require common multiple rare lower common common nominal single solid state designed work combinations large number different types microphone large differences range low ribbon large measured defined number standard microphone nominal aid defines similar set nominal classification low medium high usually high affect circuit measured connected input specific nominal value high common use common value nominal resistance known input probe designer ensure probe input exactly times figure actually plus probe cable included input probe circuit result measured distorted circuit formed probe resistance input cable generally higher
Nominal impedance