QMeaauremhnls Issue 1 1 TitleandAuthorNO. The NatureofQ,W.C. Moore........................ The Q Standard,C. L. Kangand J .E.Wachter QMeterComparison...................... AVersatileInstrument - AudioFrequencyMeasurementsUsingthe TheQMeter,L. 0. Cook............................4 5 8 Coupling UnitType564-A .......................... Circuit Effects on Q, C,L. Kang...................... Me ~ ~ u r e ~ e n t ofDielectricMaterialsandHiQ Capacitors withtheQ Meter, N.L. Riewrcmckneider................................8 AStandardforQandL ..................................12 CalibratinganInductanceStandard, J . E.Wachter ................................................15 TheRXMeterortheQMeter?, N.L. Riemenschneider................................16 AQ Comparator, I .E.Wmhter......................17 The Evolution oftheBRC Q Meter, L. 0. Cook..................................................23 ANewUHF QMeter......................................24 ApplicationsoftheQComparator, c. w. Quinn................................................25 Design of AUHF Q Meter, C.G. Gorss .......... 27 The BRC UHF Q Meter - ANewand Versatile Tool for Industry,C. W.Quinn....28 CalibrationofA UHF Q Meter, C. G. Gurm .... 29 ExternalorInCircuit* Measurementsonthe UHF Q Meter,C.W.Qitinn........................3 1 Q Meter Techniques, N.L. Riemenschneider....13 VHPBrldge, Mmmeurements& AWide-RmgeVHFImpedanceMeter, 1. Iti.Mennle................................................2 TransmissionLineMeasurementwiththeRX Meter, N .L. Riernemchncider......................3 ACoaxial Adapter fortheRX Meter, C.G. Gorss..................................................3 Titleand Author 10sLw No. SomeVHFBridge Applications, UseofSmithChartsforConverting RX Meter N. L. Riemens~hn~i$er................................6 ReadingstoVSWRandReflection Coefficient,R.Poiricr..................................0 M. L. ~ i e ~ e n s c h n c ~ ~ e r ................................16 The RX Meteror theQ Meter?, RemoteMeasurements withtheRX MeterEa- MeasurementofValta ployingH ~ l f - W a v e l ~ ~ ~ ~ fines,R. PoiPier..17 SensitiveCapacitors..22 SignalGeneratorandReceiver Impedma, UniverterSignal-to-Noistio,F. G. Mad&?3 SweepFrequencySignalGeneratorDcsi Techniques,J . N. McnniemidC.L. Ka w5 Mechanical &signRequirementsofElectronic 6 ApplicationsofaSweepSignalGene F.G.Marble................................ AMethodofMeasuringFrequency J .E. Wu5;hter ................................................9 UsefulConceptsofFrequencyModulation, WC.Moore........................................3 Instsuments,D.S.Wahlberg........................ W.C.Moore................................................10 Measurements,F. P.Montesion.................15 ACrystal-ControlledFMSignalGenerator, C.G.Gorss.............................................. UseofMwkersonSweepSignalSenerator Type 240-Pr..................................... AControl System foranFA4SignalGenerator, C.G.Gorm.................................................. Signa1 GeneratorPerformance, H.1. Lang...... TitleandAothor NoiseLimitedReceiverSensitivityMeasure- mentTechnique, J . P. VanDuyne AGeneralPurposePrecisionSignal ...........................................21 ATelemetering FM-AMSignalGenerator, H. J . Lung....................................................21 NewNavigation AidTestSet,R.Poirier........ 24 Typical PerformanceDatafortheType225-A SignalGenerator, C.S.Wi l l i am ...... AVNF Telemetering W.I. Cerncy........ A10-500 MeSignalGeneratorPower Amplifier,R . Pokier CheckingtheNewDMEandATCAirborne Equipment withtheNavigation AidTest %t, W.J . Cerney. ..............................28 .........................29 NewFMStereo ModulatorType219-A.......... 29 AModulatorfortheNewFIM StereoSystem, DesignofanImproved ApplicationsoftheSignal GeneratorPower Amplifier,C.W.Qitinn........ UsingtheFMStereoModulator,W.J . Cerney32 NewTechniquesinFMLinearity Measurements, J .P. VanDuyne....................33 ANewUnityGainFrequencyConverter, R. H.Blackwell............................................34 NewTechniques inFM FidelityMeasurements, R.N.Schulte.........................................34 Low LevelMeasurements UsingtheSignal GeneratorPowerAmplifier, CharlesW.@inn........................................35 FM-AMSignalGenera CharlesW.Quinn..... J . E.Wachter................................................36 J . P. VanDuyne.......................................30 Generator, A.N.Otis..................................31 X-YPlottingwiththeTypes 202HandJ NewSystemforCalibratingDMEandATC, Law Le r e lRF VoPLage MearuPeman@ AnRF VoltageStandardSuppliesaStandard SignalataLevel ofOneMicrovolt, C.G.Gorss.................................................. Use oftheRFVoltageStandardType245-A, W.C.Moore................................................ CalibrationofanInstrumentforMeasuring ASignal GeneratorCalibratorforRF Level Applicationsof theSignal GeneratorCalibrator, Low-LevelRF Voltages,C.G.Gorss.......... andPercentAM,R.Poirier........................21 J . E. Wachter ................................................22 14 Peak Power Illleasuwmcsnls PrecisionPeakPowerMeasmentswiththe PeakPowerCalibrator.!ayrnondPobn35 (1f TitleandAuthor TransistorM e & s u ~ e ~ e ~ t ~ withtheWF-WW Bridge,G.P. ~ ~ ~ ~ ~ R ~ $ ............................. MoreAbutTransistor~ ~ ~ s ~ r ~ ~ e n t s withthc 3. P. VanDuyne............... theTransistorTestSetandtheRX Meter, C. by. QuJnrt........................................... DiodeMeasurements on theTransistorTest Type275-A,W.J . Cerney..........................26 Film ThScknsssMeasuremento Determination ofMetal FilmThickn ApplicationsoftheMetalFilmGau_ The UseofStandardswithaFilm Gauge, BRCFilmGaugeUsedtoMeasureAircraft , A . Piip,..............................................9 Type255-A,D.K .Stevens..........................I fA.Piip.......................................................... Organic FinishThickness..............................15 Instrument Serrlcrlng ReplacingtheThermocoupleAssemblyTy pRXMeterBridgeTrimmerAdjustment CheckYourQ Readings bytheDeltaC ServiceNotesfortheRXMeterType250A 565AintheQ MeterType260A....... Method,J . E. Wachter. 4.........................................6 ternalResonating 7 8 Capacitor ofthe Q Meter, S.Walters ............ Correction ofLowQReadingonQMeter Type160A, S.Waltcrs ............................ Some NotesonInstrumentRepair.................... RF Calibrationofthe Type240A,S.Wal FrequencyCalibration S.Walters ........................ LubricationofTurretandSwitch Contacts, L.0. Cook...................................... 3 1TechniquesofSignal GeneratorInspection L.0. Cook......................................12 Low-Frequency AdjustmentofRXMet Type250A..........................................12 GlideSlopeGeneratorToneSignal.................. 13 ModificationofGlideSlopeSignalGeneratar Type232AforImprovedRF Output..........18 Type240ASeriesTubeModification.............. 22 Checking RXMeterCalibration......................25 Modification ofType265AQComparatorfar ImprovedStability..................................26 RXMeterNullIndicator................................28 AdjustmentofQ DialLock Tensiononthe T Y ~ C 280A ~~llllll.lllllll,lll.ll.r.l,..~..lllII.l,.l...,,,,.,30 Modification ofType2508 for ReducedSignal ty..................1 PART 11 INDBTXBY INSTBUMBNT TYPg Issue L .Title ........... . . . . . . . . . . . . .AVersatileInstrument - TheQMeter.......... Check Your Q Readingsby the Dilta C Method AudioFrequencyMeasurementsUsingthe CouplingUnitType564A.......... CalibrationoftheInternalResonat toroftheQMeter........................................ MeasurementofDielectric and HiQCapaciI withtheQMeter.....................8 Correction ofLowQ 4 4 Type160A...................................8 CircuitEffectsonQ............................8 FrequencyCalibrationofQMeterType260A10 AStandardforQandL..................................12 .......................13 The RX MeterortheQ........................16 The Evolutionofthe BRC Q Meter............. QMeterTechniques. eoe SearlessSignal Generators Signal GeneratorandReceiverImpedance...... A VHF FM-AM Signal Generator System........ SignalGeneratorPerf : UniverterSignal-to-NoiseRatio......................L AMethodofMeasuringFrequencyDeviation9 11 ALinearDetector for FM Deviation Measurements...............................15 nce..........................18 ATelemeteringFM-AMSignalGenerator......21 AVHF TelemeteringSignalGeneratorSystem27 DesignofanImproved FM-AMSignal Generator....................................................3 1 NewTechniquesinFMLinearity Measurements.................................... A NewUnityGain Frequency Converter NewTechniquesinFM Fidelity X-YPlotting withtheTypes202H andJ Measurements.............................34 FM-AMSignalGenerators..........................36 107 Series Univerters UniverterSignal-to-Noise Ratio........................3 AVHFTelemeteringSignal GeneratorSystem27 ANewUnityGainFrequencyConverter........ 34 ?i&W#APM Stereo Illlodulator New FM Stereo Modulator Txpe219A............29 .._...30 UsingtheFMStereo Modulator......................32 AModulator for the New FM Stereo S- ab5A Signal Generatar lu uo No. Auenerair u r p errecwonSignalGenerator21 TypicalPerformanceDatafortheType225,A SignalGenerator..........................................25 aSOA 8SgnalGenerator rower AmplPNQr A10-500 MCSignal GeneratorPower ApplicationoftheSignalGeneratorPower LowLevelMeasurementsUsingtheSignal Amplifier......................................................28 Amplifier......................................................32 GeneratorPowerAmplifier..........................35 aSSSAGliide SignrrlGeneretor GlideSlopeGeneratorToneSignal................ 13 ModificationofGlideSlopeSignalGenerator Type232A forImprovedRF Output..........18 New NavigationAidTest Set............................24 CheckingtheNewDMEandATCAirborne EquipmentwiththeNavigationAidTestSet29 8 4 0 A Sweep Signal Omnowator Techniques..................................................5 7 Sweep FrequencySignalGeneratorDesign ApplicationsofaSweep SignalGenerator ........ RF CalibrationoftheSweepSignalGenerator UseofMarkers onSweepSignal Generator Type240A..................................................16 Signal GeneratorPerfnrmarlce..........................18 Type2408 Series T~di fi cat i ~n..............22 Type2408..................................................(3 P45 Series Voltaoe Standard/ QSgni.1 OeanaarralorCaklEbrortsr AnRF VoltageStandardSuppliesaStandard Signal ataLevelofOne Microvolt..............5 Useofthe RF VoltageStandard Type 245A....7 CalibrationofanInstrumentforMeasuring Low-LevelRFVoltages..............................14 ASignalGeneratorCalibratorforRF]Devel andPercentAM...........................................21 ApplicationsoftheSignalGeneratorCalibrator22 a 5 0 A RX Mater AWide-RangeVHF ImpedanceMeter............ RXM@ter BridgeTrimmerA ~ ~ ~ $ ~ ~ ~ ~ .......... TransmissionLineMeasurements withthe RXMeter.................................................... 2 2 TiiJO No. ACoaxialAdapterfortheRXcter..............3 %meVIZFBridgeA F ~ ~ ~ ~ ~ i o ~ ~ ......................6 Setvice NatesfortheRX MeterType 25014....6 UseofSmithChartsforConvertingRX Meter toV~~~ andReflection t....................................................10 ~ w - ~ ~ ~ q ~ e n ~ y A ~ ~ ~ s ~ m ~ ~ t of RXMeter The RX MeterOrtheQ Meter..........................16 Type2SOA.......................... RX MetierNullIndicator..................................28 OAfor~ e ~ u ~ ~ S ~ n ~ ~ t i ~ i ~ y ............. MeterYet.................. 35 iPLllAMeirl pI;Cwu Qauge OR$ of theMetalFilm ~ ~ r m i n ~ ~ ~ o ~ of MetalFilmThickness............9 ..............................................11 ............................ A 4Title AQComparator............................... ApplicationsoftheQ Comparator. . . . . . . . . . .ModificationofType265A0 Cornp;or forTrnprovedStability....... l 7 S AtrrnslrtorTestSet I witht ATransistor TestSet............... Transistor CurrentGainDetermina TransistaxTestSet andtheRX 1v4c;rer Diode Measurementsan theTransistor T ....... Type2758................ l U 0 AUHF Q ANewUHFQMeter........... Design ofa UHFQMeter..... .............. ................. The BRC UHF Q Meter - ANewand CalibrationofaUHFQMeter. Adjustmentaf Q DialLock ontheType280A30 ExternalorInCircuitMeasurementsontf UHFQMeter.............................. VersatileToolforIndustry... PeakPowerCalibrator..................................35 %swIOAIIPeek Cowrr @ell;bra- PrecisionPeakPowerMeasurementswiththe TheNatureOfQ i/ W. CULLENMOOREEngi neeri ngManager Adiscussion ofthe physicalconceptsunderlying a familiaranduseful,butnot alwaysfullyappreciated,quantity- - Quality Factor. - ---- --- --- -- YOUWILLFI ND. . . T h eQ-St andard Ane w r ef er ence i nduct or f o rchecki ng Q Met er perf ormance . . . .o nPa g e5 ASe r v i c eNote Repl aci ngt he Thermocoupl e As s e mb l y T y p e565-Ai nt heQ Met erT y p e260-A.. . . . ATa b l eofBa s i cFormul as Invol vi ng9 .. . . . . . . . . o nPa g e6 o nPa g e4 AnInt roduct i onto Boont onRadi oCor po r a t i o n. o n Pa g e7 ___- __- - - - - - -e Fi gure1 . T h ei mport ance oft he quant i t yQi nt he a na l y s i sofel ect r oni cci r cui t s andcom-Here, H.J.Lang, BRCSa l e s p o ne nt sha s made t h eQ Met era f ami l i ar l aborat ory t ool .Engi neer, i schecki ng t heaccur acy o faQAe t e r T y p e260-Awi t h t he ne wQ-St andard.Q asa basisfor itsdescription,wemustlook for a physicalconcept.Wemaythenexplore theimplicationsandapplicationsofthis con- ceptina variety ofspecific situations. Letus go one step further in our analysisof theexpression@L/R,.Itisnotimmediately apparentwhythispat%iculr2r numericalratio shouldbechosentodescribecertaincharac- teristicsofcomponentsandcircuitsoverall the d h e r similarratioswhichmightbeset up.Thereasonforthischoiceonceagain refersbacktotheconceptinvolvedinthe establishmentofa definitionfor Q. Weshall see presentlythatthe basicidealeadsdirectly to a simple expression bywhichwe can deter- mineanumericalmagnitude. Inthefirstplace,theQofacircuitor componenthaspracticalsignificanceonly whenanalternatingcurrent,usuallysinu- soidalinwaveform,isflowingthroughit. The circuitparametersassociatedwithalter- natingcurrents,namelycapacitanceandin- ductance,havethecommoncharacteristicof beingcapable ofstoringenergyAn inductor storesenergyintheformofanelectromag- neticfieldsurrounding itswinding.Acapa- citorstores energy in the form ofpolarization ofthedielectric.Eachofthesesystemswill delivermostofthestoredenergybackinto thecircuitfromwhichitcameThesecom- moncharacteristicsindicatethatperhapswe shouldlooktoenergyrelationshipsforan appropriatedescriptionofthebehaviorof circuits Asmentionedabove,most,butnotallof the energy storedin an inductor or a capacitor isdeliveredbackinto the totalsystemIfwe startwiththisenergyconcept,weareina positiontoderiveafigureofmerztforthe systemintermsofitsabilitytostoreenergy ascomparedwiththeenergyitwastes Cont znued o nPa g e2 BOO NTON RA0I 0 COR P0 RAT ION BOO NTON. NEW J ERSEYTheNature Of QlJ /natingcurrents, namel)' capacitanceand in-duCl:lnce. havethecommoncharacteristicofbeing C1pabll' of Sloring energy. Aninductor enl'rgyintheformofandl'CtrOmag-neticfieldsurrounding iuwinding. A capa-citor stores l'f\l'rgyinthl' form of polariuuonofthl' dielmric. Each ofIhrseS)'SlmlSwilldeliver most of thl' Sloredenergybad:: intothl' cirruit fromwhich it caml'. 11lesecom-moncharaetl.'l"lSllcs indicatethat perhaps weshould look to enl'rgy relationships (or anappropriate description of Ihe brhavior ofcircuits.As mentionedabove, most, but not all ofthe energy storedinaninductor or a capacitorisuelivefedhackinto the total system. IfwO-Awas introduced in 1953, ils prede-cessors, lhl' Types 100-Aand IGO-A,had been giving salisfaclorylabora-lory service for aperiodof over 18y('arS, nnd had long sincehl'coml' astandardfor Qml:'asuremenls.In spite of Ihe fact Ihat, during!"{'ct'nt y('ars, the TYJX 160-Ahadproved itself ausefuLand dependabletool, it had becomeapparent, Inthelight of newdevelopments and im-provements In tbe art. thatits cir-cult had certain IimitaUons. For thisreason, lheQMeter Type260-A wasdeveloped, relaining all thevaluablecharacteristics of the 160A, but in-corporating featureswhich elimina-ted or minimized the IImitalionsoftheolder instrument.Because these designImprove-ments will often causesmall varia-tions in Qreadingsbetween thetwoinstruments, Useems desirabletotnvesllgate In detail thereasonsforsucb apparent discrepanciesandtoformulate anexpressionfor predict-ing them.-5-BOONTONRADIOCORPORATION Inorder toachieve andmaintain thesecharacteristics,theuseofa specialtubeisfoundtobeimpera- tive.TheBRC105-Aismanufac- turedandtested specificallyforap- plicationin theQvoltmetercircuit. A reviewofavailable tubetypes dur- ing the development of theType260-A confirmedthefact that this was the onlytubewhich could meetsuch re- quirements,andit wasthereforein- cludedinthedesignofthenewin- strument. Several other changesin the volt- metercircuit were found desirable. The addition of?'Lo Q"and t t ~ " scales in thenewinstrument necessitated a slightlydifferentoperating point for thevoltmetertube.In addition,the physicalarrangement ofthegrid cir- cuitwaschanged to providea higher naturalresonant frequency,andad- ditionalbypassingwas addedin the plate circuit of the voltmeter,causing theType230-AtoindicateQmore accuratelyat lowfrequenciesandatlowcapacitancesettingsofthe re- sonating capacitor o TYPICALEXPERIMENTALDATA To illustrate the differences which mightbe expected in Q readings be- tweentheQMetersTypes 160-Aand 260-A,asetofstandard inductors Type103-A was measured on twore- presentative instruments which were selectedtobeasnearly average a spossibleafter acareful survey ofQ readings onseveral hundredproduc- tion units.Figure 6is aplotofthe readingsobtained,andfigure 3in- dicates the percent difference in these readingsvsfrequency.Notethat thesegraphs apply only toinductors with Q values in the ranges indicate d . Ingeneral,the percent differenceat anyfrequencyis proportionalto Q. FORMULAFORPREDICTING QREADINGDIFFERENCES The empirical formula at the bot- tomofthis page has beensuggested byR.E. Laffertyto describe the dif- ferences in&readings obtained on the twoinstruments. - -Term C 1 .. -~~ L50- 500kc- 5-10mc -10-50 mcI This formula is the result ofcom- biningactualmeasurementstaken withbothaverageinstruments in a form indicated by theknown theoreti- cal differences in measuring circuits described previously.It will beob- served that the termsoftheformula aregroupedaccordingto frequency domain.Term Arepresents the dif- ference ininputconductance between thetwoQ voltmeters,t er m B cor- r ect sfor the differenceofinsertion resistancevalue,and term C com- pensates for theinductance ofthein- sertionresistorintheType160-A QMeter.Thelattert er m was de- rivedusingthe average valueof83 pphyforthisinductance.It wi l lbe notedthateacht er m isequalto1 outsidethefrequencyrangespeci- fied.Thus,from 50 to 500 kc,only t er m A is significant, whilefrom 500 Figure3. Difference inQreadingsobtainedbymeasuringaset of 103-Ainductorson both160-Aand260-A,withthereadingsoff helatterusedasobose.Eachlinela- belledwith acoil numberindicatesthepercentdifference inreadingsobtainedby meas- uringthesamecoil, throughoutitsresonantfrequency range,onbothinstruments.The lineslabelled35uuf, 100uuf, and400uufrespectively, indicatethepercentdifference inQreadingsresultingattheseinternalresonatingcapacitances. d FREQUENCY(K C) Figure4.Valuesof thefactorK, for useintermAofcorrdationequation. kcto5 mc,all t er ms are approxi- mately 1 and the twoinstruments will havegoodagreement.From 5 to 10 mc,t er mBbecomessignificant, while terms A and C may be disregar- ded.Above1 0mc,B andCmust be used.In general,the needforcor- rection is proportionalto themagni- tude. Itshouldbenoted that this cor- relationequationdoesnotaccount fortheeffects ofthe harmoniccon- tentofthe oscillatoroutput ofearly QMetersType160-Aat the upper endsofthe lowfrequency bands.Q w ozIO k20 n kj 30 ' 40305070100 200300 w U LLW W Y RESONATINGCAPACITANCEM UT Figure5 . Colculoted percentdifferences inQreadingsbetween260-A(usedas base)and160-A,atthreevaluesofQasreadon the 260-14. -6- BOONTON RADIO CORPORAnON200300/'.//'0

Qllao-'"

0 .. -0''/1'100lkcI0This formula is the resuitof com-bining actual measurements takenwith bolb average InslrumentsIn aform indicated bytbeknown theoreti-cal differences inmeaauring cirCuitsdescribedpreviously. It will beob-servedtbat thelermsof theformulaare grouped accordingtofrequencydomain. TermA representslhe dif-ference InInpul conductancebetweentbe two Qvollmelers. termBcor-recls for the differenceof insertionresistance value, andtermC com-pensates for theInductanceof lhein-sertion resistor In theType 160-AQMeter. The lattertermwas de-rived using theaveragevalue of 83 for this Inductance. II will benoted that each termis equal to 1outside the frequency rangespeci-fled. Thus. from50lo 500 kc. onlytermA Is significant. whilefrem500""Fi,,,,. 5, Co/c"I",'" ,...,cent aiH.,.nc..In0, ...al",. Mt....n260... (....., o.&a..) anJ J60... , U'robalanCt' ofthE> RXMetrr bridgt'circuit Is rwCt'ssarily s('nsilivc toE'X-IrtlTtol'lysmall variationsInInternalcircuit Cll.PQcitancl'. 11 ispossibh'thnl mlnut\' shiftsin UIf' rclalivt' po-sition of circuitcompof'l('nls. causedbyexccsslv{'ly rough handling in shljrping, t'lc., mayaUt'rthrdfl'ctlvecll.po.clly ('Dough to makeit impoe-slblt' loobtainanull indicallononthchlght'st frt'quI'ncyrang(' by adjustingZERO BALANCE conlrols, "R"and"C...Inmost cases, thissituaUon canIx' corrl'cledbylhefollowing screw-driversdjustmE'ntt1. Allow Ihr instrumt"nt 10 warmup, set the oscillator frt"quf'ncy al 200mc, and adjusllhl> delt>ctor luningcontrol as descrlbttd in lhft InslructlonManual, wUhtbe Cpdialat 0 andRpat 00.Z. With a screwdriver, pry upthe- small melalcap locatedneartbcrear of tbegroundplat.eontop of tht'lnBtrumellt. Thisprovides accesstoa small lrlmr:nercapacitorhaVingavertical, slottedadjusting shaft.3. Rotate the''R'' knobandDott'whethftr tbe nulllDdicator reading de-crea.ses \YIlb fa) clockwise, or(b)counter-clockwise, rotation.FI,,,,. I, ", obtained, rotatethetrimmeranothcr 1/8 turninthesanw dlrec-UOD. Continue tblsprocedure untilbalanct'canbE> obtained.5. CbeckthebalBllCE' at afrcq-uencyof250mc andrepe-at thE" aboveadjuslmt'nt If necessary.Correct null indication cannotbe obtained while the screwdriverfor aligning tool) Is Dear orIncontactwiththetrimmer shaft.,,

MT8rmBBIBLIOGRAPHY1. "The Natul'e of Q", W. CullenMoore, BRCNotebook, No.1.2. "AlternatlngCurrt'nt MeasurtngInstruments as DiscriminatorsAgalnsl Harmonics", irvingWolffProc. IRE, AprIL, 1931.3. "RF Microvoltages", Myron C.Selby, National Bureau or Stand-ards.frequen::yrange.Thecorrectlonequallon andotherdatapresenledInthisarticle aretheresuU of information oblalnedfromaverageQ Meter readings, and donotallow for variallonswithinspecifiedtolerances. ApplicationInIndividualcases mayrequirestudy of thepara-meters ortht> Inslruments concerned.,'MeFREQUENCY,'00 '"o_.....M-WO lieIill-A ""''-le' 1.1 me....1GI:elr.,..11 U ..........tlGl: ""1'""'1-

arl,.-IoIllrad" ,-r ItlllO..,....,., 1_II1M kcJ:>e ftt therefore behave thesame as the antenna system withrespect 10 abilityof the receivertoabsorbenergy. Failureto meet thiscondition invalidates the signalgen-erator as a substitutefor theantenna.Let ualook briefly at anInteresttngs\luatlon. FaUure to takeIntoaccountthe Internal Impedance of anantennasystemCllll vely easilyieadto an er-ror of2: 1Intberealizablesensitivityof a receiver as compared to themeasured value. It would require achangeof 4: 1in theantt"nnapowerofthe transmitter at arUed distancetocompensate(or theapparent errorof2:I Inthesensitivity of thereceiver.Otberconaldt"rations, such asslg-rul-Io-noise ratio orselectivity. mayImpose contradictory requlremen18onthe input impedance characteristics ofa receiver as comooredw th '''e.1. 1 BOONlONRADI OCIORPORAT,ION THE BRCNOTEBOOKis published fourtimesayearbytheBoontonRadio Corporation.I tis mailedfveeofcharge t oscientists,engineersandothermter- estedper.ronsi nthecommunications andelectronics fields.The contents may bereprintedonlywithwrittenpermis- sionfromtheeditor.Yourcomments andsuggestionsarewelcome,and shouldbeaddressedt o: Editor,THE BRCNOTEBOOK,BoontonRadio Corporation,Boonton,N.1. of power transferwhichtakesplaceas wevarytheratioofload toantenna resistance.Thiscurveshowsthat themaximumpowerattheinput ter- minals ofthe receiver is obtained when the receiver inputimpedancematches the antenna impedance.The maximum is fairlybroad,buta relativelysmall shift downward in theinputimpedance of the receiver resultsina very large changeintheamountofpowerde- livered tothe receiveras comparedto theeffectofan equalincrease in the receiverinputimpedance. SELECTIVITY Upto this point wehave beendis- cussing the title of this paper, namely: ''Tomatchor nottomatch",Weare nowfacedwiththesecondquestion. ttIfnot,whynot?''Thecurve wepre- sentedinFigure1 shows the wayin whichpoweris transferred from one resistivecircuit to another.Asim- ilarrelationshipexistsforcoupling betweenprimariesandsecondaries oftuned transformers. Asthecoupling is increased,the effective Q oftheresonant winding de- creasesuntilapointis reached at whichtheQ drops to one-halfthe un- coupledvalue.Atthispoint(i.e. critical coupling), there is the optimum energy transferbetweenthecircuits. However,thatvaluebfcoupling which produces optimum energytrans- fer hassimultaneouslydropped theQ ofourresonantselectivecircuitto one-halfandthereby degeneratedthe selectivityofthefrontendofthere- ceiver.Inordertoobtainbetter selectivitycharacteristics,wemay deliberatelymis-matchthereceiver tothegenerator toreduceloading on the resonant circuit.Wewi l l shortly findouthowthismis-matchcanbe accounted forin our'measurements. MIS-MATCHINGFORIMPROVED MI S- MATCHI NGFORIMPROVED SIGNAL-TO-NOISERATIO Anotherconsideration whichmay lead to adeliberatemis-matchofthe receiverto theantennaimpedanceis thenecessityforimproving thesig- nal-to-noise-ratiooverthatwhich wouldbe,obtainedfromaperfect match, 3* The noise and the signalar e inter- mixedin theantennaandthereceiver should select them as favorably as pos- sible.Thenoisevoltagegenerated in the antenna is proportional to the square rootoftheantennaimpedance.The noisepowerinducedinto thematched inputcircuitofareceiveris indepen- dentofthereceiverinput impedance. The signal power foragiven voltageis, however,afunctionoftheinputim- pedance ofthereceiver.Theratio ofsignaltonoisecanthereforebeaf- fectedbydeliberatelymis-matching the receiver to theantennaimpedance inexchangeforalossinmicrovolt sensitivity. 1 ,S IfGNA LGENERA T 0 R CALIBRATION Havingseen above thatthereare reasonstomatchandreasons notto match thereceiverinput to theanten- naimpedancethereremainstoin- vestigate the question:"Ifnotmatch- ed,whatthen?"Itshouldbecare- fully notedthattheIRE standards re- quiringtheuseofadummyantenna saynothing whatsoeverabout theim- pedanceofthereceiver. b OPENCIRCUITVOLTAGE OUTPUTVOLTAGE "1%ZXGENERATORCALI BRATI ON Fi gur e3.Outputvol t agecal i brat i onfora generatorhavingi t ssourceimpedance equalt o thecharact eri st i cimpedanceoftheoutputcabl e.Touseasignal generator intel- ligentlywemustunderstandhowthe output system behavesunderdifferent conditions.Signal generatorscan be dividedroughlyintotwoclasses: a.Lowsourceimpedance,andb, matchedsourceimpedance.Inlow source impedance generators, the out- puttransmissionlineisdriven di- rectlybyapick-uploophavingthe lowestpossibleinductance.Ina- matchedsourcegenerator,alowin- ductance pick-uploop providesa very low impedance source ofvoltagewhich feedsthroughamatchingresistorto the output cable.The valueofthere- sistor is carefullycontrolledto. match thecharacteristicimpedanceofthe transmission line. Theoutputmetersanddials of signal generatorsof both thematched andlowinternalimpedancevarieties arealmostuniversallycalibratedin termsofthevoltagedevelopedat the outputjackonthefrontpanelofthe generatorwhenthisjackis termina- tedinaresistiveloadequaltothe characteristicimpedanceoftheCO- axiallineortheratedoutputim- pedanceofthegenerator. Theheartoftheproblemlies in thelengthofcoaxialcablecommonly used to connectthepointofgeneration of theradiofrequencysignalsto the inputtothereceiver.Atthefreq- uenciesgenerallyencounteredin communicationsandtelevisionthis lengthofcablecan approach andex- ceed1/4wavelength.A1/4wave- lengthpieceoftransmission line has atransforming property for bothim- pedance andvoltagewhichactssome- whatlikeateetertotter,themid- pointofwhichisthecharacteristic1 impedanceoftheline.Alow-loss 1/4 wavelength pieceoflinedriven by alow impedance source will producea veryhighvoltageattheopencircuit endoftheline.Conversely,ifthe drivingsourceimpedanceis high the outputvoltagewi l l below.Ifthe sourceimpedanceequals thecharac- teristicimpedanceoftheline,the outputvoltagewillequaltheinput voltage. Inmatchedsignal generators the calibratedvoltageisfedthrough the characteristicimpedanceofthegen- eratorandtheconnecting cableto the matchedterminatingload.Inorder forthedial to becalibratedin terms ofthevoltage,E, developedacross theloadaloneitis necessary to de- liver twice this voltage,2E, to thein- puttotheinternalgeneratorimped- ance.Thismeans thattheopen-cir- cuitvoltageavailableatthefront panel,2E,wi l lbetwicethatobtained, E,when theoutput jack is terminated inamatchingimpedance,and hence twicethedialcalibration,asshown inFigure 3. Lookingbackinto thegenerator fromtheendoftheConnecting line oneseesa properlyterminated line. ThereforethelengthoflinehasnoL effectonthevoltageattheoutput, -2- BOONTON RADIO CORPORATIONTHEBRC NOTEBOOKII PIib/uINJJOllrImln a J"" b,Ih, &0111011RAdio 11;1IfJm/,a fru oj rhtUg'10lti'",Uf1, "ndollNr mIn'nita ptTJOl/I m lIN rOIlJWIIIIIUalIO'U"lid ,lttlrrJnltS jUJdI. Th, rom,nll mil'IN"f'Tmt,JOl//J utlh ",'nll'lI !""mlIon Jromth, ,ailor. Yo....,. rOnlllltll',4Ita 11I11'lltonl ""aIholtlJ In to; Edllor, THEBRC NOTEBOOK, Boomo" RAd,oCorporallOn, Boolllo", N./.of power transfer which takesplace aswe vary the rallo of loadto antennaresistance. This curve shows thatthe maximumpowerat the Input ter-minals of the receiver Is obtained whenthe receiver Input Impedance matchesthe antenna impedance. The maximumIs falrlybroad, but arelatively smallshift downward intheinllUt Impedanceof the receiver resultsIn avery largechange in the amount of power de-livered tothe receiver ascomJXlredtothe eHect of an equal increaseIn thereceiver input impedance.MISMATCHING FOR IMPROVEDSELECTIVITYUpto thispoint wehavebeen dls-cussingthe tille ohhis paper, namely:"Tomatch ornOI to match". We arenowfaced with the secondquestion.''If not , wbynot?" Thecurve wepre-sented in Figure I sbows thewayInwblch power Istransferredfromonereslslive circuit to anOlher. A sim-Ilar relallonsbipexists for couplingbetween primaries and secondariesof\Uoedtransformers.AsthecouplingisIncreased, theeffectlveQoftheresonant winding de-creases until a point Isreachedatwhich theQ dropsto one-half theun-coupled value. Ai this point (1.1.'.critical coupling), thl.'re Is the opt imumencrgy iransfer betweenthccircuits.However, that value or couplingwhich produces optimum energy trans-fer hassimultaneously droppedtheQof our resonant selective circuli 10one-half andthereby degeneratedtheselectivityof thefront end of there-ceiver. In order 10 obtain hellerselecllvltycharacteristics, we maydeHberately mis-matchthe receiverto thegeneratorto reduceloading onthe resonanl Circuit. We will shortlyfind out howthis mis-malchcan beaccounledfor in our measurements,MIS-MATCHING FOR IMPROVED RATIOAnother consideration which mayleadla a deliberatemis-match of thereceiver to theimpedanceIsIhe necessity ror improving the sig-nal-to-nolse-rallo over that whichwould be obtslDe'd (rom a perfl'Ctmatch.Tile noise and the signal areinter-mixed tntheantenna andthereceivershould select them as favorably as pos-sible. ThenOIsevoltage generatedinthe antenna Is pl'oportlonal to the squareroot of tbe antenna Impedance. Thenoise power InducedInto lhematchedInputcircuitof areceiver Is Indepen-dent of thereceiver input impedance.The signal power for s givenvoltageIs,however, a function of the Input Im-pedance of thereceiver. Theratio ofsignal to noise can thcrefore be af-fected bydeliberately mts-matchingIhe receivertotheantennaImpedanceIn exchange for a loss In microvoltsensitivity.SIGNAL GENERATORCALIBRATIONHavingseenabovethat there arereasons to match and reasonsnot tomatch therl.'celver input 10 theanlen-na impedance there remains 10 In-vestigalethe questton: "If not malch-ed, what lhen?" 11 should be care-fullynotedthai themEslandardsre-quiringthe use of a dummyantennasaynothing whatsoeverabout the Im-pedanceof thereceiver.Fi'J'He3. Outp'" .....lfOrulilwof;OfI f1H..rlte,olo< l>ovi"9 it. ._". ''''"..,., ,.e'l",,1 I.. the ",.",...".,i" ... i.".,J 0'the o",put"",Io'e.Touse a stgnalgeneralorIntel-ligentlywe must understand bowtheoutput systembehavesunderdifferentconditions. Signal gen"x>"/2'" 1f and)'1" (\'1+ llf. Also,tanhyl " lanh(0'1j1f) ". tanh (\'1,and if (\'1 is small, Ihen, tanhal" 0'1,andtanh)'1'" a!.SubstitutingIn(5) arove,Zll", zJZn. + ZoO'IJ\Zo + ZRal)Dividingnumerator and denomlnalorof IhefrucUonon theright by ztl, weobtain(6)If the half wavelength cable Isopen-circuited (Le. ZR"'oo), (5) wHlre-duel' 10(I)ZII '(Z.J:::C ,1Zoat '" Z\I nepers. Th"nresistive and Is measured directlyon the Rp dial oftheRXMeter.CONCLUSION1I wll1 be observed that all themeasurements describedin thisartl-cle are simpleand direct, without in-volved comp.1tatlonandcorrections.In all cases, relatively shortlengthpieces of cable are used and measure-ments are made directlyat theRXMeter terminals without the useofcoaxial connectors. Itmaybeof In-terestto notethat abalancedHnecanbetreatedin thesamefashionas co-axial lines whena ''balun'' orsimilardevice isusedin connectingIt totheRXMeter.F'gur. 2. Tile"utll"., m,,,suring til. clKt,,,cl,.i.tlc Imp,d""c, of ".il""l I,,,gtll of RC-58!Ucobl. On rill RXMete(4)(2)where the phase constant (J '" 2'1':/>",and>.. '"wavelength. Now, iJ thelineIs 1/4 wavelength long, I'">"/4and211" ;\, lr131 '"x - '", 4 2For the purpose of deriving ameansof measuring thentlenualion ofa IransmisSlon line, the general ex-pre5sioll for a linewithloss Isgivenbelo.v .SubsUtutlng in(1) above,(+jZo) Zo'ZI"'Zo -.-=-,"d(+)ZL) ZLIf the line Is1/8 wavelengthlong andis short circuited, then 1= ;\'/8, ,81 ..lr/4 radianor 450, nndZL'"O. Sub-slitutingIn(1), (3)(+jZSin 450}ZI '" 200 '" X .ZoCoo45In Ii similar manner it canbeshownthat lhe Input Impedance of a1/6wavelength line that is open cir-cuitedIs,-6-THENOITEBO'OK . ,I , I .OUTERCENTERCENTER IN G CONDUCTORCONDUCTORGUIDE bh ADAPTER PLATE 5OHM T E RMINATION WRE'KHMOUNTING SCREWS Fi gure7 . Componentsoft heCo- axAdapterKi t Type 575-A.Theki t is suppliedinacon- veni ent woodenstoragestand,notshown. ACoaxialAdapterForTheRXMeter C. G.GORSS,DevelopmentEngineer SoonaftertheRXMeterType 250-Amadeitsappearanceinthe fielditbecameapparentthat: inad- ditionto measurementofcomponents onthestandardbindingposts,many oftheapplicationsinwhich thisnew instrumentwasbeingutilizedin- volvedtheuseofcoaxialcablesand fittings.Theevidentneedforsome convenientmeansofcouplingsuch components,fitted withstandardco- axialconnectors,totheRXMeter measuringterminalsresultedinthe design ofa special adapterunit.This unit which, together with the necessary accessories,isnowavailableto RX Meterowners in kit form: is disigna- tedasthe'To-axAdapterType515- A.I 'DESIGNDETAILS The adapter itselfconsistsoftwo separate elements;a cylindricalouter conductor about 1 1/ 2 inches in length. thebaseofwhichisgroundedto the terminalplatewhenmountedonthe RXMet er , anda tapered centercon- ductor whichis fastened to theHIbind- ingpoststud.To mount the unit,an adapterplate,suppliedwiththekit, isfirst fastened to theterminalplate oftheRXMeter,Thisplatehasa large-diametertapped hole whichcen- t er saroundtheHIpoststud,After theHIpost clampingnuthas beenre- movedandthecenterconductorhas beenscrewedfirmlyoverthestud, the outer conductor is t urwd downinto thisholeuntilits basemakes contact with the terminalplate,Theopen end oftheadapterthenforms astandard TypeNfemale connector. Whentheadapterisinstalled, ordinary measurementsrequiring the use of the binding posts are easilymade merely byunscrewingthe outer and in- nerconductors oftheadapterandre- placingthe bindingpostnuts.Thea- dapterplatein no way interferes with such measurements. Alongwiththe adapter andadapter plate, the kit includes awrench for re- movingthegroundbindingpost base nut,acenteringguideforaccurate positioningof the outer conductor, four screws for fasteningthe adapterplate, and a special 50-ohmcoaxial termina- tion. The unit is designed to haveacon- stantcharacteristicimpedanceof50 ohms.Allsurfacesarerhodium- platedtoinsuregoodcontactandto matchthe plating used on the RXMeter terminalplate, The termination, whichis usedin obtainingpreliminarybalanceofthe RXMeterbridge,is equipped witha Type N male connectorfor direct con- nectionstotheadapter.Likethea- dapter,itisactually ashort section oftransmission line,Itscentercon- ductor, howeveris actually aspecial highfrequencyresistor.Theter- minationproducesa voltagestanding waveratio ofl ess than1 , l Oup to 800 mc APPLICATION Whentheadapterisinstalleda coaxialelementmaybeattached and measuredatanyselectedfrequency aftertwominorpreliminaryadjust- mentsof the RXMeterbridgecircuit controlshavebeenmadeto establish thecorrect "zerobalance"condition. Thefirstadjustment,made with no- thingattached to theadapterand with theRpdialset at- , consistsofob- taininganullindicationbyalternate adjustmentoftheZERO BALANCE R controlsandtheCpcontrol.This establishesthecorrect''resistance zero"ofthe circuit. Thesecondzero balanceadjust- mentismadewiththe50-ohmterm- inationmountedinplaceonthea- dapter.This timea nullindication is obtained by means ofthe RandZERO BALANCE C controls, witgtheCp dial at 0.This establishes the correct "re- actance zero. ' I Actually, it has theef- fectofadjustingtothepropervalue the characteristic impedance of a short internalconnectingsection(several centimeters in length) betweenthe RX Meterbindingpostandthephysical point onthe bridge circuit at whichthe measurement is actually made.Since thecharacteristicimpedanceofthis sectionisnot,initself,50ohms, thatvaluemustbeestablished syn- thetically by properadjustment ofthe ratioL/C.This is automatically ac- complished bythesetting oftheZERO BALANCE 0 control describedabove. Although the co-axadapteris use- fulinfacilitatingmeasurement ofthe characteristics ofcables and otherco- axialelements,probablyitsmost importantapplicationisinproviding forthemeasurementofimpedances remote fromthe RXMeterterminals. Whentheproper techniquesare used, itispossibletomeasureanimped- anceattheendofasectionofcoax line withthe same accuracy with which it can bemeasured directly at the RX Meter terminals.Such measurements may, ifdesired, be madewithrandom- lengthsectionsof50-ohmcoax,in whichcasetheresultsmust betrans- formed by means ofa Smith Chart'zor thefamiliartransmissionline equa- tions inorder toobtaintheactual im- pedanceof theunknown.In this case, theshortinternalconnection,men- tioned above, betweenthe bindingpost and bridge, becomes part ofthetrans- missionlineanditseffectivelength -7- THE NOTEBOOKof Iransmisslon line. liscenter con-ductor, howev('r, isactually aspecialhigh frequency resistor, The ter-mlnatlon produces avoltagestandingwaveratio of lessthan 1.10 upto800mo.APPLICATIONWhen the adapter Is Installed acoaxial element may beattachedandmeasured at any selected frequencyafter two minor preliminaryadjust-ments of the nxMeterbridge circulicontrols have been madeto establishthecorrect "zerObalance" condition.The first adjustment. madewith no-thingattachedtotheadapterandwiththe npdial set at "'" , consistsof ob-taininga null Indication by alternateadjustment of the ZERO BALANCE Rcontrols and the Cpcontrol. Thisestabl1shes the correct "resistancezero"of the circuit .The second zerobalance adjust-ment is madewiththe50-ohm term-inalion mounted In place on the a-dapter. Thistimeanulllndlcalionisobtained by means of theRpandZEROBALANCE C controls, wltfi theCp dialat O. This establ ishes the correct "re-actance zero." Actually, II has theef-fect of adjusting to the prOpel' valuethe characteristic impedance of a shortInternal connectingseclton (severalcentimeters Inlength)between theRXMeter binding post and the physicalpoint on tbe bridgecircuitat whichthemeasurement is actually made. Sincethe characteristic impedance of thissection is not, In itself, 50 ohms,that value must be establishedsyn-thetically by properadjustment of theratio Lie. Thisisautomatically ac-complished by thesetting of the ZEROBALANCE ocontroldescribedabove.Although the co-ax adapter isu s e ~ful infacHitatlngmeasurement of thecharacterlsl1cs of cables and other co-axial elements, probably Its mootimportant application is Inprovidingfor the measurement of Impedancest"emotefromtheRXMeterterminals.When thepropertechniquesare used,It is possible to measure anImped-ance at the end of a section of coaxline with the same accuracy withwhichit canbE' measured directlyat the RXME'ter terminals. Such measurementsmay, ifdeslred, be made with random-length sections of 50-ohm coax. Inwhich casetheresultsmust be trans-formed by means of a Smith Chart"orthe famlliar transmission Hne equa-tlonsinorder toobtainthesctual im-pedanc('oftheunknown. Inthiscase,the short Interoal connection, men-tionedabove, betweenthe bindingpostand bridge, becomes part ofthetrans-mission line and Its effective lengih5 OHMTERMINATION\WRENCH MOUNTI NGSCREWSmovt'd and the center conductor hasbeen screwed firmly over the stud,the outer conductor Is tun,,,ddown Intotbis holeunlil (Isbasemakescontactwilbtheterminul plate. Tbeopen endof the adapter thenforms astandardType Nfemaleconnector.When the adapt'r Is Installed.ordinarymeaSUl'ementsrequiringtill'use of the binding posts art' easily mademerelybyunscrewingthe ouler and in-ner conductorsof theadapterand re-placing thebindingposl nuts. Thea-dapter platE' in no way interfereswithsuch measurements.Alongwilh the adaptel' andadapterplatC', the kit includes a wrenchforre-moving the ground binding post basenut, a centeringguide for accurateposit ionlng of the OI.lter conductor, fourscrews for fastenlngthe adapter plate,and a specia150-ohmcoaxial termlna-lion.The untl is designE'd to havea con-stant characteristic impedance of 50ohms. All surfacE'S are rhodlum-platE'dto Insure good contact andtomatchthe pial iog used on the RXMetE'rterminal plate.The-termination, which isusedinobtainingpreliminarybalance of theRX Ml"Ier bridge, Is equippedwithaType Nmail" connectorfor dirE'ct con-neclions to the adapter. Likpthe a-dapter, it Is actually ashort sectionIICENTERINGGUIDECENTERCONDUCTOROUTERCONDUCTORADAPTERPLATE..DESIGN DETAILSThe adapter Itself consistsoftwoseparateelementSl acylindrical outerconductor about 11/2 inches In length,the baseof which Is grounded10 Hwterminal plate when mounted on theRXMeter, andataperedcentcrcon-ductor which is fastenE'd fo the HI bind-Ing post stud, Tomount theunit, anadapter plate, supplied with the kit,Is first fastenedtotheterminal plateof the RX Meter. This plate has alarge-diameler tapped hole which cen-terS around the HI post stUd. Aftertheinpost clamping nut has beenre-Soon after the RX Meter TyJX'250-A madl' Its appearanc(' in thefie Id Hbecame apparent thai, in ad-ditionto measurement of componentson the standard binding posts, manyof the applications In whlcnthl;; newinstrument was being utilized in-volved tht> use of coaxial cablesandflttings. The evident need for somE'convenient means of coupUng suchcomponents, fittedwithstandardco-axial connectors, to the RX Metermeasuringtl'rminals resulted In thedeslgnofaspecial adapterunit, Thisunit which, togethE'r with the necessaryaccessories, Is nowavailable toRXMeter owners Inkit form, isdisigna-ted as the"Co-axAdapter TyJX' 515-A. "FI9u'e 1. ComJ>Onents -ment maybemadeon the QMeter bythefollowingmethod:Connect the coil to be- measuredtotheQMeter COILterminalS(Figure1).ResonatetheQMeter, calling the os-cillator frequency dial readiog fl andthe calibrated variable capacitordialreadingCl (Cl should be preferablyin the lower part of the scalc).Readjust the oscillator toa consid-erably lower frequency f2 equal tofl/n. Restort> resonanceby readjust-iogthevariablecapacItor. calling thenewreading C2' The distributed ca-pacitancc isthenCz-nlCln2- 1actanceconditionsvsfrequencywill beseenasin Table1, columns 2and 3.The Q Meterdisttnguishesreadily be-tween condittonsa, h, c. thus provid-Ingan accurate determination of theself-resonantfrequency, as will be ex-plainedtn detail with theaidof column4.Inmaking themeasurement the firststepisthe determination of leads re-quired to connect the unknowninductorto the Q Meter CAP terminals (1).These leadsare then permanently con-nectedtothe CAP terminals andtheinductor is disconnected. Thts pro-cedure tllinimizes the effects of leadcapacitance on the self-resonant fre-quency.Next. theQMeteris resonatedwithawork or accessory coil (preferablyshielded, such asthe Types103-A or590-A) connectedtotheQMeterCOILterminals(see Figure4). The fre-quency chosenshould be intheregionFigure4. Induet' OrMe"suremenl.P"'olle' of theestimated self-resonant frequen-cy of theInductor to be tested. Nowconnect theunknownInductor Lx totheCAP t('rmlnal leads previouslyestab-lished. Re-resonate the Qmeter bymeansof thecapacltanc('dial Cc, not-ing the direction of movement of thisdial asreferred totheoriginal setting.Unless the unknownInductor isfoundtobenon-reactive at themeasurementfrequency first chosen, the test pro-cedureisnowto be repeated ata some-what higher orlowerfrequencyas de-terminedby reft>renceto Table1, col-umns 2 and 4. Successive frequencyadjustmcnts will eventually achievethe desired colHiiUon whercthecapac-itance dial reading for resonance Isunchanged as a resUlt of connectingthe unknown inductor to the Q MeterCAP terminal leads. The unknowninductor Isthennon-reactive and self-resonanl at thefrequencyIndicnted bytheoscillator dial.CHOKE COILSA chokecoil, to provideproperiso-lation characterlstips, must exhibita high Impedance throughout its op-erating frequency range. Failure tomcet thisrt>quiremenl mayresult inlow operating efftciency. frequencyerror In calibrated circuits. etc.The QMeter provides an ideal meansfor the measurement of choke coil char-acteristics. Awork coil. preferablyshielded, is connectedtotheQMeterCOILtcrminals (Figure4). Leads ofshort length maybeused, if required,10 conncct the unknown choke coil tothe QMeter; these leads arcnowtobeattached tolhe QMeter CAP ter-minals (1) but the choke coil istobedisconnected. The workcoil tsreso-Ilated at the frequency of measurement,calledf, theQ reading being called Ql.and the calibraled variable capacitorreadingbeing called Cl. Temporarilyremove the Q Meter CAP terminalieads. if used, andnolt> the increaserequired in the calibrated variablecapacitor readingfor resonance; calltheIncreaseCLI re-connecttheleads.Next theunknownchokecoil Lx is con-nectedtothe QMeter CAP terminalsleads and the calibrated variable ca-pacitor Is readjusted for resonance.Call the QreadingQ2 and tbe capacitorreadingC2.The above procedureshouldbe re-peatedat other frequencIeswithintheIf f2 is madeexactly equal to fl!2,then,An average of several measurementsemployingdifferent values of Cl andC2 wHi improve the accuracy of theresults.SELFRESONANCEThe self-resonant frequency of aninductor, t. e. the resonant frequencywith nothIng connectedexternally totheinductor termtnals. canbereadily de-terminedwith the Q Meter. Looking"--'" into theterminalsof theinductor, re-TABLE1INDUCTORSELF-RESONANCEDATA(1 ) (2) (3) (4)QMeterInductor CapacitanceCon- Reactance Dial Testditton UFrequency Is Will Be Reading,Belowself-resonance Inductive Increasesb At self-resonancc Non-reactive Nochange,Aboveself-resonance Capacttive Decreases-3-operating rangeofthechokecoil(CL maybeassumedtobeconstaqtand neednotbere-checkedwhen thefre- quencyischanged); Theeffectiveparallelresistance! Rp, andeffective parallelreactance, Xprofthechokear e QI QzRp= w(C1 +CL)(Q1- Qz) and 1 w( C z - C l )x p =where Rp,Xpar einohms w=2nf(cycles) Cisinfarads. 1 . 5 9 ~ 1 0 ~ x Q1 Qz Or , Rp= f(Ci+CL]ki- Q2) 1,59105 f(C2- C1) andXp= where Rp,Xpare inohms fis in megacycles Cis inmicro-micro-farads. NOTE:Thesignofthequantity (Ca-Cl )indicates thetypeofeffec- tive reactance,A positivequantity indicatesinductivereactance.A negativequantityindicatescapaci- tive reactance, MUTUALI NDUCTANCE AND CRITICALCOUPLING (a)Themutualinductanceandcoef- ficientofcouplingofRF coils may bemeasured onthe QMeterat high frequenciesbythefamiliar method oftenemployedatlowfrequencies withaudio frequency bridges. Thismethodisusedforlarge couplingcoefficients,i.e.0.5or greater.Fmrmeasurementsar e made(on theQMeterCOILtermi- nals)atorneartheoperating fre- quencyandpreferablyatone fre- quency. MeasureL1andL2separately. ThenmeasureLa(mutualaiding ) withL1andL2connectedseri es aiding, andLb(mutual bucking) with L1 andLaconhectedseri esbucking (Figure 5). Themutualinductancethenis La - Lb 4 La-Lb M---. Thecoefficientofcouplingis M = - . u =4 % - v zBOONTONRADIOCORPORATION L(MUTUAL)MUTUAL aAIDINGLb(BUCKIYt) Figure5. MutuallnductanceConneLJtutis, LI L2-- firstandsecondcoupledcoi l s, re- spectively. Ifthemeasurementsaremade at one frequency 4 whereC= QMeter tuningcapacitance necessaryforresonance withmutualaidingcon- nection,mutualbucking connection,andsinglein- ductorsrespectively. (b)WithRFcoilsmostcommonly usedthecritical coefficient of cou- pling(i. e,Ithe condition wherethe resistancethatthesecondarycir- cuitatresonancecouplesintothe primarycircuitisequalto there- sistanceofthe primarycircuit)oc- curs atalowvalueofcoupling co- efficient.Design-wise,thecriti- calcouplingconditionisimportant because it yields themaximum value ofsecondary currentandit may be readily determined as follows. Connectoneofthetwocoils to theQMeterCOILterminalswith thesecondcoilopen-circuited(see Figure6) andadjust theQMeterfor resonance,ReadQ1. Nowcomplete thesecondary circuitand, bymeans ofitstrimmer:resonateittothe samefrequencyasindicatedbya minimumQ reading,Q2. IfQ2/Q1equals0.5thecoils ar ecriticallycoupled; ifgreater than0,5thecouplingis l essthan CT63 COUPLED COILSLO7GN D Figure6. Cri t i cal Coupling.Ct-Secondary coi l Trimmer. couplingisgreaterthancritical. Theseresultswi l l bewithr e-spect to thecoilsonly.Ifit is de- siredtoincludetheeffectsoftube andcircuitloading,resistorsdup- licatingtheseloadingeffects should beaddedto thecoils beforemaking themeasurements. GAI NOFCOUPLEDCOILS TheQMeterisessentiallyagain measuringdevice, Le . ,Qis measured bydeterminingtheratiooftwo volt- ages.This instrumentis thusreadily adaptable to thegainmeasurementof coupledcoils withinits range. Forexample, a transformerused to couplealow-impedanceloopantenna to areceiverinputmay bemeasured. Referring to Figure7, thetransformer primarycircuitincludingtheloop(a coilmay beused to simulate the loop) isconnectedtotheQMeterGNDand LOterminals.Thetransformersec- ondaryisconnectedtotheQMeter GNDandHIterminals.TheQMeter injectionvoltage thus excites the trans- former primarycircuit andthetrans- formersecondary voltageis fedto the Q voltmeter.Adjustmentofthecali- bratedvariablecapacitorCcforr e-sonance wi l l nowyielda"Qreading'' whichis numerically equivalent to. the transformercircuit gain.TheQscale readsgain directly when the"Multiply Q By"meteris set toxl ,By completionofthe proper connec- tionstheabovemethodcanobviously beextendedtoinclude stage gainmea- surements. t S U MM A R Y Wehavedescribedsome ofthe"ex- tra-curricu1ar"usesto which a Q Meter maybeput.Noattempt wasmadeto writeanexhaustive article and weare surethatourmanycustomershave devisedotherwaysofutilizingthis versatileinstrument. that, when anRFmeasurementproblem is at hand,theQMetermay do thejob. May wedraw thisconclusion: -4 - BOONTON RADIO CORPORATIONIFigure7. TronsformerGo;nMeasurement.SUMMARYWehave describedsomeof the "ex-tra-curricular" uses to which a Q Metermay be put. Noattcmpt was madetowritean exhaustivearticleandwe arcsure that our manycustomers havedevised other wnys of utilizingthisversatileinstrumcnt.Maywe drawthisconclusion: that,when an RF measurement problemIsat hand, the QMeter may dothejob,coupling is greater than critical.These results will be withre-spect tothe coils only. If itIs de-sired to Include the effects of tubeandcircuit loading, resIstors dup-llcatingtheseloading effectsshouldbe addC'd tothecoilsbeforemakingthe measurements.GAiN OF COUPLED COILSThe QMeter Is essentLallya gainmeasurlngdevice, Le.QIs measuredbydetermining the ratio of two volt-ages. ThLsinstrument is thus readilyadaptabletoIhe gain measurement ofcoupledcoilswithinitsrange,Forexample, a transformerusedtocouple a low-Impedance loop antennato areceiver Input maybemeasured.Referringto Figure7, thetransformerprimary cirCUit Lncluding the loop (acoil maybe usedto simulatetheloop)is connected. to th(' QMeter GNDandLOterminals. Thetransformer sec-ondary is connected to the Q MeterGNDandHI terminals. TheQMeterInjection voltagethus excites the trans-Cormer primary circuit andthetrans-fOImer secondary voltageIsfedtotheQvoltmeter. Adjustment of th(' cali-brated variable capacitor Ccfor re-sonance will now yIeld a "Qreading"which isnumerically equIvalent to. thetransformerclrcui! gain. TheQscalereadsgain directlywhenthe"MultiplyQ By" meter Isset to xl.By completionof thE'proper connec-tionsthe above method can obviouslybe extendedtoinclude stagegainmea-surements,Figure 5, Mutual Incluctonce Connections,LI L2 lirS! oncl uconcl couplee/ coils, rotspec,;.".lrIf the measurements are madeat onefrequency(...L_--'-) ~,"=CaCb ....., CICIK: "---=----'4where C'"QMeter tuning capacitanceneCE'SS(ll'y for resonancewith mutual aiding con-nection, mutual buckingconnection, and single in-ductors respectively.(b) With RF coils most commonlyused the critical coefficient of cou-pling (I. e., thecondition wheretheresistance that the secondarycIr-cuit at resonance couples into theprtmarycircuit Is equal tothere-sistanceof theprimary circuit) oc-cursat a lowvalue of coupling co-efficient. Design-wise, the criti-cal coupHngcondition Is importantbecauseIt yields themaximum valueof secondary current andIt maybereadUy determinedasfollows.Connect one of the twocoilstothe Q Meter COiL terminals withthesecond coil open-circuited (seeFigure6) andadjust theQMeter forresonance. Read Ql' Nowcompletethesecondary circuitand, by meansof its trimmer, resonate It to thesame frequency as indicatedbyaminimumQreadIng, Q2.IfQJ Ql equals 0.5 the coilsare critically coupled: If greaterthan 0.5 the coupling isless thancritical, and If less than 0.5 theFigure 6. Criticol Coupling. Ct.S.cone/o'rcoil T,immer,coupling isM4The coefficIent ofLa - LbK = =4 ~ ~operating rangeofthe chokecoil (CLmay be assumed tobe consta'}t andoeed not bere-checkedwhenthefre-quency Is changed).The effective parallel resistance,Rp, andeffectlveparallel reactance,'Xp, of the choke areQl QzRp= ---------------W(CI +CLI (Ql - Q ~MUTUAL INDUCTANCEANDCRITICAL COUPLING(a) Themutual Inductance andcoef-ficient of couplingof RFcoUs maybe measuredontheQMeterat highfrE'quencies by thE' famUlar methodoften employed at lowfrC'quencleswith audIo frequencybridges.This method Is used for largecoupling coefflclents, I. e. 0.5 orgreater. Four measuremC'nts aremade (on the QMetC'r COILtermI-nals) at or near the operating fre-quency and preferably at one fre-quency.Measure Ll and L2separately.Then measure La (mutual aIdIng lwith L 1and L2connC'cled seriesaidIng, andLb(mutual bucking)withL1andL2connectedseries bucking(Figure5).The mutual tnductance then IsLa- Lbw(CI-Cl)whereRp, Xpare in ohmsw.. 2 iii (cycles)C is In farads,1. 59xl05x QlQ,Or, Rp'"r lCI-CL) ~ l - Q,)L59xl05andXp =""df(C2 - CIlwhereRp' xpareInohmsfIs in megacyclesCIs inmlcro-mlcro-farads,NOTE: The sign of the quantity(C2-CI) Indicates thetypeof effec-tlvereactance. A positivequantityindicates Inductive reactance, Anegative quantity Indicates capaci-tivereactance.-4-THENOTEBOOK BADWEATHERFLYING EDSONW.BEATTY,Chief Pilot It i I D 1 TheAuthorstandingbesidetheBRCBeechcraft Bonanza.Theaircraft i sful l y equippedfor in- strumentflight andprovidesavaluablesourceo finformationrelevantt o actualaircraft operation underallflight conditions.Insetupperl ef tisa typicalInstrumentLandingSystemGl i de Slope fi el dinstallation.TheBRCGlideSlopeSignalGeneratorType232-A(center)providescali- bratedRFsignalsandonallGlideSlopefrequenci es-thusprovidingmanufac- turersandserviceorganizationswithaninstrumentcapableo fsimulatinganyorallsignals transmitted i ntheGlide SlopeSectionoftheInstrumentLandingSystem.modulation Everbeendelayedattheairport by weatherorarriveseveralhoursbe- hindschedule?Mostofus have,but haveyounoticedrecently these delays ar e notoccuring as often?Wehere at BRCfeelthat withourtest equipment weare helping tocontribute a part to- wards reducing theseoccurances. Today, on board a modern high speed air transport,wegivelittle thoughtof the problemsbroughtaboutby thein- creaseinspeed,trafficdensityand type ofweather nowconsidered flyable. Justasan example,an aircraft trav- eling at 150MPHwith acourse er r orof5 Owillbeapproximately 4miles off course after30minutestime.How- ever,at 350 MPHwiththe same course er r or for30minutes,theaircraft wouldbeover8-1/2miles offcourse. Now commercial flights ar e beingmade dailywithlittlemore than part ofthe airport runway being visible.Experi- mentalflightsar ebeingmadeunder visibility conditionswheregreat diffi- cultyingroundortaxiinghandlingis encountered.Thewriterhadanex- perience recentlywhen,rollingdown therunwayafterlandinginaheavy fog, the control towercalled by radio from1/4mileawayandrequested "Haveyoulandedyet?'' Theseimprovementsinairnaviga- tionandcommunicationshaveall been broughtabout through electronic equip- ment.Theprimaryaids nowusedar e Omnirangefornavigation,Instrument LandingSystemforblindlandingand VHFCommunications. THEVORSYSTEM Omnirange,sometimesreferredto asVOR(Visual,Omni-directional Range),isarecentdevelopmentin radio navigationaids.TheOmnirange is designed, as ar e other air navigation systems,tofurnishdirectionalguid- anceto an aircraftinspace.Itis the primaryaidin point-to-pointair navi- gation.The word Omni is derived from Latin"Omnis"meaningall.These stationsar es onamedbecausethey haveaninfinitenumberofcourses, whereas,thefacility they replace has only fourcourses. AnOmnirangestationmightbede- scribedasaverylargewheelwith 360spokes(theoreticallyaninfinite number) withthestation being thehub. Anyoneofthespokesmightbechosen asaguideinspace.This is accom- plishedelectronicallybycomparison ofthephasedifferencebetweenthe audio modulationoftwo radiatedradio frequencysignals,thedifferencein phasevarying with changeinazimuth. Themodulationononeofthese signals isnon-directionalandhasa constant phasethroughout360degreesofazi- muth.Thisiscalledthereference phase.Inordertoseparatethetwo signals forcomparison in thereceiver andconverter,alOKCFMsubcarrier is usedto carry thereferencesignal. Thephaseofothersignal rotatesat a speed of1800 RPM andvaries in phase with azimuth.This i s called thevari- able phaseandi s producedbya motor driven goniometer feedingan RF volt- ageinto fourantennae(two at a time). As thegoniometerrevolves,theRFvoltagefedintotheantennae(180 de- grees apart) variessinesoidally at the rateof30cpst oproducearotating field.Thesystemis set ups o at mag- netic norththe referenceandvariable signalsar eexactlyinphase. Fr oma pilot'sstandpointtheopera- tionisquitesimple.Otherthanre- ceiver,converterandantennae,there arefourbasicunitsintheaircraft. Although somemanufacturers combine theseunitsforsimplicity,weshall discusstheprimarytype. Thepilot'scontrolsare illustrated inFigure1andconsistsof: 1.FrequencySelector(conven- tionalreceivercontrol) 2.Azimuth Selector 3. DeviationIndicator (with signal strengthindicating flag) 4.SenseIndicator Furtherdescribing each unit: 1.Frequency Selector:tunesr e-ceiver to desired station frequency whichisidentifiedaurallywith code (recorded voicealso onsome stations). 2.AzimuthSelector(CourseSe- lector):selectsthe desiredazi- muth(or track)tocontroldirec- tioninspace. 3.DeviationIndicator:indicates the difference between theselected azimuthandpresentpositionor ,- 5-THE NOTEBOOKEDSOI'l W. BEATTY, CbiefPilolBAD WEATHERflYING.tIsystems, to furnish directional guid-anceto anaircraft inspace. it istheprimaryaidinpOint-to-point air navi-gation. Theword Omlli Isderived fronlLatin "Omnls" meaning aiL Thesestations are so n.1med because thcyhave an Infinite numbel" of courses,whcreas, thefacilitytheyreplacehasonlyfour courses.An Omnirange station might be de-scribed as a verywheel with360 spokes (theoretically an Infinitenumber) wllhIhestationheingthehub.Anyoneof thespokes might bechosenasa guide{n space. This IspUshed electronicallyby comparisonof the phase difference between theaudiomodulalion of tworadiatedradiofrequency signals, the difference Inphase varyingwllh changeina1'.imuth.The modulationononeof these signalsIs non-directional and has aconstantphase throughout 360 degrees of a1'.i-muth. This is called the referencephase. III order toseparalll the twosignals for comparisonin thereceiverandconvcrtel", a JOKCFM subcarrierisused to carrythereferencesignal.The phase of other signal rotatesat aspeed of1800 RPMand variesinphasewitha1'.imuth. ThisIscalledthevalf-able phaseand isproducedby a motordriven goniometer feedingan RFvolt-ageintofour antennae (twoat atime).As the jl;onlometez" I"evolves, the RFvoltage fedinto theantennae (180 de-greesapart) variessinesoidally at therate of 30 cps to ploouce a rotatingfield" Thesystem isset upso at mag-neticnorththerefel'cnce undvurlablcsignals are exuctly in phase.Fromapilot'sstandpoint theop"'ra-tion Is quite> simple. OtherIhanre-ceiver, converte, andantenn:lC, thereare four basic units in the aircraft.Although somemanufacturerscombinethese units for simplicity, we shalldiscuss the primary type.The pilot's contl'ols arelllustratedIn Figure1andconsistsof,L Frequency Selector (conven-tional recelv("r conilol)2. Azimuth Selector3. DeviationIndicator (withsignalstrength indicatingflag)4. Sense IndicatorFurther describing eachunit:1. Frequ("ncy Selector: tun("s rC'-celver to des il("d station frequencywhich [s Identified uurallv withcode (recorded voicealso soml:'statlonsl.2. Azimuth Selector (Course Se-lector): selects thedesiredazi-muth (or trackl tocontrol direc-lioninspace.3. DeviationIndlcaton indicatesthe difference between thesclcct{'d(l,1'.lmuth and pl"esent positlonor,mental nights are being made undervisibility conditionsWhel"egreat diffi-cultyIn ground or taxIIng handling isencountered. The writer had an ex-periencerecently when, downthe runwayafter landing In a heavyfog, thecontrol towercalledbyradiofrom 1/4 mile away and requestt..>d"Have you landed yet?"Thcse fmprovements In air navlga-ilonand communications haveaUbeenbrought about through electronic equip-ment. Tile prlmary aidsnowusedaleOmnirangcfor naviP;atlon, InstlumentLandingSystemfor bUnd landing andVHFCommunications.THE VOR SYSTEMOmnirange, somelimes refe'Ted toas VOR (Visual, Omni-direc!lonalRange), Is a recent development Inradionavigationaids. TheOmnlrangeIs designed, as areother air navigationEver been delayedat theairport byweather or arrive several bours be-hindschedule? Most of ushave, buthaveyounoticedrecently these delaysarenot oecuring saoften? Wehere atBRC feel thatwithour test equipmentwearehelpingtoconlribulea partto-wardsreducing theseoccuranccs.Today, on board amodern high speedairtransport, wegiveHtdethought oftheproblems brought about bytheIn-crease tn speed, traffic densityandtype of weather nowconsidered flyable.Justasan example, anaircraft trav-eHng at 150 MPHwithacourse errorof 50 will beapproximately4 milesoffcourseafter 30 minutes timc. However, at 350 MPHwith thesame courseerror for 30 minutes, the aircraftwouldbe over 8-1/2 mllesoff course.Now commercial nights arc being madedaily with Httle morethan part oftheairport runwaybeing visible. Experi-.. Aulho, standingbesidoIh.. BRC a.... ehc,ofl Bonanza. Th.. ol,erofl is fully oqulpp..d{a' i,,strum.. nl flight ond providesa voluoblesou,eeo{ informal Ionro/ovont 10 oeluol oi,e,oftope,orionundo, all //;glo, condillons. In1 upp.. , left I. a typical '''sl'u'''''''1LandingSyst.mGlide Slope/ield In$/ollollo". fI,e BRC Glide SlopeSignol Gon..,oto, Type 2J2_A(c..nler' provide. co/I.&,ol..d RFsignolo and modulation On all Glid. Slope {,equendu-" llou. p,ovlding"",nuloc-lure,s ond s.,viee o,gon,.ollon.../II. 0" Inst'u"",n' "opohle 01 slmulo'ing any 0' 011.ignol,I,onsmlffedin,I... Glid.. SlopeSoclionof ,Io../n$/,u",",'" Landing Sy.lem.-5-BOO MARKERBEACONGLIDESLOPEOMNlORLOCALI ZER INDICATORLIGHTDEVIATIONDEVIATIONIN01CATOR /(VERTICALNEEDLE)INDI C AT 0 R \\ I \ FREQUENCYSELECTOR \ OMNl OR LOCALIZER SWITCH AZI MUTHSELECTORSENSEINDICATOR Figure7. ThePilot'sVHFRadioControlsinstal craft Bonanza. conversely,theazimuthfroma stationto theaircraft' sposition. Two ormorestations maybe used toestablishposition.Alsoin- cludedis an alarmindicator which indicateswhenausablesignal i sbeingreceived. 4.SenselIndicator (To-FromMe- ter):determinesthe phasecom- parisontoestablishthe quadrant (i. e.northazimuth or south azi- muth). Atthepresenttimetherear e392 omnistationsnowinusethroughout theUnitedStates. THEI L SSYSTEM Wehavediscussedpoint-to-point ai rnavigationandalthough theomni- rangemaybeusedas a landingaidit is nottheprimarytype.TheInstru- ment Landing System (ILS) is the more effective typeandconsideredthemost practicalfromacost andoperational standpoint.Itspurposeis to provide apredetermined,precisepathtoa landingrunwaywithoutvisualrefer- ence totheground. fledintheinstrumentpanelof theBRCBeech- The systememploys three elements: 1.Localizer 2.Glide Slope 3.Outer andMiddleMarker 1.Localizer:provides the direc- tional guidancetoanddownthe landingrunway. 2.Glide Slope:providesthealti- tudeguidancewhileapproaching ontheLocalizer. 3,OuterandMiddleMarkers: providefixes orlocationsonLo- calizerandGlideSlope. Inordertodescribetheoperation ofILS,weshallconsidereachele- mentseparately. TheLocalizerprovidesthe direc- tionalguidancebyradiatingafield patterndirectlydownthecenterline oftheinstrumentrunway.Thecar- r i erismodulatedattwo frequencies, 90and150 cps,witheachmodulated carri erappliedtoa separateantenna system.Theyar earrangedsothat while ontheapproachend of theinstru- mentrunwayfacing theantenna, the90 cpssignalpredominates ontheleft and the150 cpsonthe right.With this ar- rangement,an equalsignal ratio of90 to150cpsisprojecteddownthein- Toexplaineach element: 7 5 MC108MC112k cl l 8 MC1 3 2 MC M4 MC 320.3 MC3 3 5 MC+MARKER*LOCMIZER-*OANI DIRECTIONAL+-COMMUNICATIONS-*MILITARY--,*NOTASSIGNEDTO ---GLIDESLOPE- BEACONRANGEGROUNDAIRAIRCRAFT I T OTO AI RGROUND I NTONRADIOCORPORATION strument runway and continuing offinto theapproach area. Theequalsignal zoneisdesignedtobeapproximately 5O wide, TheGlideSlopeprovidesaltitude guidancewhileapproachingon the lo- calizer.This is accomplished in much thesamemanneras thelocalizer with theexceptionofthe direction ofequal signalzone.Thecarri er is modulated at two frequencies, 90and150 cps with eachmodulatedcarri ersuppliedto a separate antennasystem.Thesesys- temsar earrangeds oan equal signal zone,ortoneratio,is2-1/2'to30 fromparallel to the earthssurface and isapproximatelylo wide. TheILSmarkers, therear etwo, called outer and middle, serveas radio fixestocheckprogressonLocalizer andGlideSlope.Bothar e vertically- radiated,low-powersignals(always 75MC)elliptical in shape and directed so thecenter is directlyunderthelo- calizeron-coursesignal.TheOuter Marker is located between4 and 7miles fromrunwaythreshold.Thecarri er ismodulatedat400cpsandkeyedto emitcontinuousdashes.Themiddle marker is located between1250 ft.and 3500 ft.fromrunway threshold.It s carri eris modulatedat1300 cpsand keyed to emit alternate dots anddashes. Theequipmentaboardtheaircraft (other thanreceivers andantenna) con- si st softhefollowings 1,FrequencySelectors:(one each forLocalizerandGlideSlope). 2,DeviationIndicators:(two me- ter movements insame instrument eachwith signal strength indicator alarm)e 3.MarkerBeaconIndicator Lights:(fixedfrequencyre- ceiver)" From thepilotstandpoint,the con- 1.FrequencySelectorforLocal- izer(108-112MC):tunes the pro- perlocalizerwhichisidentified aurally.GlideSlope(329.3to 335MC)istunedwithaseparate controlandmayonlybeidenti- fiedbyflagalarmoppositede- viationindicator. 2.DeviationIndicators:provide guideforfollowingLocalizerand GlideSlope, the verticalindicator forLocalizerandhorizontalfor GlideSlope. trolsserve as follows: Figure 2. F. C. C. FrequencyAssignments -- Aircraft NavigationandCommunications. 4 BOONTON RADIO CORPORATIONFigur. 1. Th. Pi/or'sVHFRodioConlrols ins rolledin,h. inslrulMnl po...1 01rile GRCGeed,.croftGononzo.THE ILS SYSTEMstrument runway and continuing off intothe upproacharea. The equal signalzone is designed to be approximatelySOwtde.The Glide Slope provides nltitud(>guldnnce while approachtng on the10-c:llizcr. This Is:lccomplisil(>dinmuchthesame manner asthelocalizerwiththe exceptionof the directton of equalsignal zone. The carrier Is modulatE'-ways Operation Training Series, Bul- letin No.l, Washington:Government printing Office, - QREADINGSBytheDeltaCMet hod JAMESE.WACHTER,Proj ect Engi neerI I I Cr J A C A CV i =voltageacrosstheQMeter capacitor at a pointother than resonance . AC=capacitance between two points ofequalvoltage( Vi ) , oneon eithersideof resonance. Qc=circuitQ=wL/RwhereR includesalllosses in thecoil and theQ Metercircuit. Itisworthwhiletonoteherethat sincetheQ-voltmetersofallBRC QMetersar elinearwithrespectto voltageandQ, equivalentvaluesof indicated Q may besubstitutedinthe ratioVr/V1.Equation1 containsan approximationwhich is negligiblewhen Qisgreaterthan100. Aneasy level at whichtomakethe ACmeasurement is atthehalfvolt- ageor halfQ points( Vr/V1=2.0), in whichcasetheprecedingequation becomes CrQc =3.4641-(2) AC Anotherfrequentlyusedlevelisat the0. 707voltageorQpointswhere: 2 Cr Qc= 4C Anoutlineoftheprocedureusing equation(2)andapplicabletoallQ MetersmanufacturedbyBoonton RadioCorporationis: 1 . SettheQMeteroscillatorto thedesiredfrequency. 2.Adjustthe XQcontrol forunity. 3,Connecta shielded inductorre- quiringacapacitancesetting nearthemaximumavailable readingforaQReadingnear fullscale. 4.IfQ MetersType160-Aor260- Aar ebeingchecked,setthe vernierscaletozero. 5.Resonatethecircuitwiththe internalresonatingcapacitor. a.Record theresonatingcapa- citanceindicatedontheQ capacitordialas Cr. b.RecordtheQatresonance asindicatedontheQvolt- meteras& r e6.With theinternal resonatingca- pacitor(vernier capacitoronQ MetersType 160-Aand260 - A) detunethecircuitoneitherside ofresonance tothepointwhere the QindicatedbytheQvolt- meteris equal toQ,./2. Record thecapacitybetweenthesetwo pointsas AC. 7.Toavoider r or s duetomech- anicalandelectricalbacklash all settingsoftheQcondenser shouldbeapproachedwiththe samedirectionofrotation.To minimizeer r or s inreading all settings andreadingsshould (3) - .Fi gure2. CapacitanceCurveof theQMeter Circuit. I 7 THE NOTEBOOK3. MarKer Beacon Lights: Indi-cates by flashing aignal whichmarker isbeing passed over, also,these slgp.als may be identifiedaurally.At the present tlme there are 146ILSsystemsIn operationIntheUnitedStates not includingmilitaryInstalla-tions.Withthe assignment of newfrequen-cies following World War II (See Figure2) there was tremendous need for asta-ble Signal Generator between 88 andHOMe. The BRe Signal GeneratorType 202-B has been accepted andpurchased by The Civil AeronauticsAuthority and widely used throughouttheIndustry. Duringthe developmentof the Omnirange system. a phaseshift was encountered Inthe Type 202-Bwhich was not desirable. In1948, acompletely newSignal Generator, theType211-Awasannounced, eliminat-ing this problem. Due to Increasingdemandfor acrystalcontrolledstableGlide SlopeGenerator, theType232-Awas placed on the market in 1953.All these units are approved by TheClvll Aeronautics Authority as partof the llecessaryequipment to obtaina CAAllcensedRadio RepairStation.Already theCAAis making additionstothe Omnirange and lLSsystemsbyequipping them with DME (DistanceMeasuring Equipment)j at presenton-lyinhightrafflc density areas. Thistogether with Radar Monitoring of airtraffic, bring closer the dayof no-weatherdelays.BIBLIOGRAPHYHurley, H. C., Anderson, S.R., andKeary, H. F. ,"The Civil AeronauticsAdministration VHF Omnlrange".Proceedingsof I. R. E., Volume39.December, 1951, pp. 1506-1520.U. S. Air Force. AAFTechnical Or-ders, Number 30-100F-l, 30-100F-2.U. S. Department of Commerce. Air-waysTraining Series, Bulletin No.3Washington, Government PrintingOffice,U. S. Department of Commerce. Air-ways Operation Training Series, Bul-letlnNo.l. Washington: Governmentprlntlng Office,CHECK YOUR QREADINGS By the Delta CMethodJAMESE. WACHTER.(1)Figure 2. CapaciranurveJ on Q M.,., Type 2&O_A.FI,."e 2. Inpur yo/to,. requl.ed 10' Xl .ndln,0"0Mufllply Q By _r.., ove, I,.,que"cy '0"9*0' Coup/I", U,,;I.F. Use WithQ Metet Type160-AAlthouShdesignedprimarilyforoperationwiththC'QMClet Type260A, thC'CooplingUnit may be used with theolder QMcterType t6O-A if the following recrovoltswhile s....eeping. lIS 1C3hgl.' is sufficient..ly low10 permitof anexternal 20 db attenuatorto obtain outputs down tl:I 0.1 microvolt.F 19u,e 6. Int.reonneclions lor stUdy 01eobl. artd eabl. terminationeharaeterla.tics.Seleetivity of S'nllle ShillesThe systemof connection in 2 isfor receivers, filters or amplifien.Theterminatedrfcable (a ohmis connectedinto the input of the'lest circu,t.Thedetector ofthetest circuit iJconnecredto lhe: ourker adder circuit insweepsignal(input impedance 1 ohm). The useof .. I'lo'erpsignal source i$DOl limiledtocornr.lete recei.cnor ampli.6cn, ooWC"Ver. So ongasarr.tn,gementsaremade to avoid anr effect onsensitivityorseltivity of the circuit under test by theImpedance of lhe: rl output of the S...eepSigllal Gentnllor or of the: the selec_tivitysensltivilycharacteristiaof anycircuilnuy be nIlsenedwithinthe sensitivitylimitsof the oscilloscope beinguscc:I.A convenIent method of omerving the pusband of &singlestage-appears in FigureTheourput of the! SweepSignal Genera!Orconnectstothegridof theluhe: whichcontains lhe test in iu plate circuit. Abroadbanddetectoris connectedto thep/4teof the foliowing stage through a couplingcondenser. The lowinputof thedetector lowersQof the circuit in theplate of this tubeSOmaterially as to itseffect on lhe final rt.':5ult insignifiunt. tunedcircuit of tubeV I isoperatingunderits normal conditionanditssensilivity.selee.tivitycharacteristic anbe obsl'rved on theoscilloscope.Studr of Pus BIndCharlderistiuTheQof Ikepass bandof atest circuitcan he: approxlmatdydeduced byusc of a5""erpSIgn&! gt'nerator. As discussedabovethe responsecune of a circuit unbe d,s.plaredon&namphtudevs. frequencygraphontheface of.. uthoderaytubC'. The rmrl;.ingsysternof the Sweep Frequency S,g01llGenerator makes 11 posiilble toidcnllf)' anyfrequency along the honwat:al axis. Sincelheresponse Inthe' vert.cal directIOnontheoscilloscopeislinear, apoint 0.707 Ii the:distance from the aero or reference line 10 thepeakof the response cune can be locatedon each side of die peak. FlOm the frequencymarking the frequency differenceTHENOTEBOOK ( n f )betweenthesetwopointsandthefre- quencyofthepeakcanbeobtained.Qcan -thenbeobtainedfromthefollowing formula:Q= f, Af Adjustmentor StaggerTunedCircuits Broadpassbandsareoftenobtainedby adjustingtheresonantfrequenciesofsuc- cessive singletunedcircuits to slightlydiffer- ent frequencieswithinthe desiredpassband. The overall result is a relatively flat pass band broaderinfrequencythananyone ofthein- dividualtunedcircuits. Toadjustthistypeofamplifier,itis normallyquickertofirstresonateeachindi- vidual circuitto the properfrequencywitha cwsignalgenerator.Aftercompletionof thisprocedure,theoverallpassbandcon- figuration can be investigatedandtouch up adjustmentmadewithasweepsignalgen- erator.TheSweepSignalGeneratorType 240-Aisexcellentlysuitedtothisprocedure sinceitoperatesasacw(withorwithout AM)orsweepsignalgenerator,without thenecessityofdisturbingtheinputorout- putconnectionstothe testcircuit.AVacuum TubeVoltmetercanbebridgedacrossthe inputtotheverticaldeflectionamplifierin- putoftheoscilloscopeforthesinglefre- quencywork.Theoscilloscopeofcourseis usedfor theoverallinvestigationandtouch up.Sincetheoutputmonitoringandat- tenuationsystemisequallyapplicabletocw andsweepworkthesensitivitycaneasilybe checkedundereithercondition. Studyof CableCharacteristics The characteristics ofhigh frequency cables maybeinvestigatedbyuseofasweepfre- quency signal generator.In Figure 6 asweep signalgeneratorisshownconnectedtothe inputofalengthofhighfrequencycable. Alsoconnectedto theinputofthecableisa widebanddetector.Thelowfrequency sweepvoltagefromthesweepsignalgen- eratorisconnectedtothehorizontaldeflec- tioninput ofthe oscilloscope. The RF signal, sweptorfrequencymodulatedatalowrate of60 timespersecond,isfedinto thecable. Reflectedsignalfromimperfectionsinthe cableortheterminationarrivesbackatthe u Figure7.Oscilloscopedisplayindica- tingamplitude of reflected energy from a terminationcoaxialcable. inputafinitetimelater.Sinceduringthis finitetimetheinputsignalhaschangedto anewfrequency,anaudiodifferencefre- quency(inputfrequencyminusreflectedfre- 1quency)appearsacrosstheoutputofthe detector.Theamplitudeoftheinputsignal isgreatandconstantandthereflectedfre- quencyamplitudeforanearmatchissmall and variable.The amountofenergyreflected from the end ofthe line depends on thecor- rectnessoftheterminationandvariesfrom zerofor a perfectmatchto a finite valuepro- portionaltothemismatchformismatched lines.Since theterminationimpedancewill, ingeneral,varywithfrequency,theamount ofenergyreflectedwillalsovary.Theaudio frequencyfromthedetectorappearsonthe oscilloscope,Theenvelopeamplitudeofthe displayisproportionaltotheinstantaneous reflectedsignalandtheabscissaispropor- tional tofrequencyofRFinputasshownin Figure 8.Diagram of equipment and con- nectionsformeasurementoflinearity of FMdiscriminator. Wi t haperfectterminationoverthefre- quencyrangeinquestion,variouscablescan be observedfor imperfectionsin construction. Aperiodicvariationindielectric constantof thecableinsulationwill exhibititselfonthe oscilloscopedisplay. Adjustableresistanceloadwillpermit quickdeterminationofthe Z,for long cable lengths. Thelinearityof FMDiscriminators TheSweepSignalGeneratorType240-A providesapowerfulmethodofdetermining thelinearityofanFMdiscriminator.The methodisindicatedinFigure 8.Alowfre- quency(60cps)sweep,adjustedtosweep thefull frequencyrange ofthediscriminator, andahigherfrequencysweep(400cps)is fedintotheEXTsweepinputoftheSweep SignalGenerator.Thehighfrequencyvolt- age isadjustedto sweep onlya small fraction ofthefrequencyrangeofthediscriminator. Ineffectthehighfrequencysweepexplores theslope ofeach sectionofthediscriminator while it isslowly movedfrom sectiontosec- tionbythe low frequencysweep.The output isdetectedandpassedthroughahighpass filterwhichpasses onlythe resulting400cps note.Thedisplayoftheamplitudeofthis notevs.thelowfrequency.sweepaffordsa visualdisplayinwhichtheslopeofthe amplitudeoftheenvelopeofthe400cps note is proportionalto FM discriminator line- arity.A constantamplitude indicatesalinear discriminatorwhereasavaryingamplitude indicatesavariationinlinearity. TheStudyofCrystalModes The rapidlocationofthe several frequency modesatwhichacrystaloscillatesisimpor- tantbuttediousbydiscretefrequencymeth- ods. TheSweepSignalGeneratorType240- Aprovidesafrequencysweep on whichindi- vidualfrequenciescanbeidentifiedbythe markersystemincludedinthegenerator.h crystal,however,hassuchahighQthat sweep rates must be very low to preventring- ingandspuriousresponses.Byusingan oscilloscopewithlowfrequencysawtooth sweepavailable,the240-Acanbesweptat frequenciesof1 or2cpsbyconnectingthe oscilloscopesweepoutputtotheExternal SIGNAL GENERATOR .re9.Equipmentarrangementfor measurementofquartzcrystal character- istics . Sweepofthe240-A.Thesystemisthen connectedasshown inFigure 9.Byvarying thecenterfrequencyofthe240-Aandits sweepwidththecrystalcan beexploredfor responsesoveraconsiderablefrequency range. Extensionof theFrequencyRange The lowestcenterfrequencyoftheSweep FrequencySignalGeneratorType240-Ais 4.5 megacycles.Atthisfrequencythesweep frequencycapabilitiesoftheinstrumentare 2 1 % to1 3 0 %ofcenterfrequencyor 2 4 5KC to: t 1.35 MC.Forapplicationsin televisionvideoamplifiersbothfor colorand blackandwhite,andaircraftnavigationre- ceiverintermediatefrequencyamplifiers, lowercenterfrequenciesand/orbroader sweeps are required.Both these requirements can be met byuse oftheUniverterType 203- BwiththeSweepFrequencySignalGen- eratorType240-A.The203-Bconsistsofa broadbandmixerwithlocaloscillatorat70 MC. followed bya broadbandamplifierwith a50ohmoutput.Thegainofthe203-B is set at unity.Figure1 shows the240-A, 203- Binameasuringset-up.Inusethe240-A istunedtoafrequencyequalto70MC plus thedesiredoutput centerfrequencyfromthe system.Sweeps from2 0 . 7MC to1 1 5 MC areavailable.Singlefrequencyoutputsun- modulatedorwithAMmodulationcanbe obtained.Thussinglefrequencyorsweep outputsaremadeavailableovertheband widthofthe203-B whichis0.1 to25MC. Summary The SweepSignalGenerator isapowerful toolofconsiderableflexibility.Itnotonly savesconsiderabletimebutmakesrefine- mentspossibleincircuitadjustmentandde- velopmentwhichwouldnotnormallvbe posbleTHEAUTHOR FrankG.Marb1e.scareercoversabroadfiela of engineeringexperience: designG develop- mentwork forPhilco:coordinatoron various governmentprojects;two yearswith Western Electricselectrical research divisionG en- gineeringadministrativepos t s withPruttG WbitneyAircraftG KayElectricalCo.Mr. Marblebasbeenwi t hBoontonRadiosince I951G aVice-president-salessince1954. MI . Marblehasa BS inEE(MississippiState ColleQe 1934) G anMSinEE(M.I.T.1935). 3 THE NOTEBOOK(nf)bctvo'ttllttldetWOP0InU andthefrequency ofthepe:U: canbe obt.a..inM. Q antnm be' obt"ned from the follo....ingformub.: Q- L>.. St'IliSet Tuned Circuitsare often byadjusrmg rhe rcson.lnt frequencies of successive singlerunedcircuiu to slightly dilJerent frequencies ....ithinthe desiredpass band.The overallresult is a relatively flatpass bandbro.lderin frequencyth.ln.lnyone of theindividu.dtuned circuits.To adjust this type of amplifier, it isTlOl'11Ullyquiaer tofirst resonateeuhindio... idullcirroilto the proper frequencywithacw sign.tl After complerion ofIh,s procedure, Ihe (we",,11 p.lSS bimd configuruion =be investigatelayof the :llJIpliludeof thisl1ClI:e \"S. the lowfrequencys..ct'palJordsavisw,l display in whICh rhe slope of rhtamphtU + az ::+I 2 0z L G-I i e - 2(0-3 .A > 4- 40100 2W300400500 DIALREADINGLUCFigure 2.CorrectionChart, 7 THE NOTEBOOKFigureI. of equipment that canbe inthecalibrationof ,h. in-terno/ resonatingcopacitor of aQ Meter. H.reoreQ MeIers Type260.Aand0GRprecisioncapocito' Type722D. of CalibrationA. Calibration of mainQ Capacitor.(I) Set the QMeier, NO.2, which tobe used as the r('sonaoce indicator, to450"",fandturnonthepo,,'('r. Moumon the instrument a suitably shieldedcoil that wiJl resonate between 200 kcand kcSlleh as the 103A32.(2) Conneathe precision C1lpacitor tothe Hi and Gnd terminals of the indicatingQMeterthrough ashort pieceofcoaxial cable. Nowset lh.. capacitorinthe indicating QMeter, No.2, totheminimum"alue of 30",,.(3) Connect lilegroundedterminal oftheprecisioncapacilOr10 the Gnd terminal on lhe Q Meter being C1llibraled(No1) withaNo. 18slrande10 being assumed:==

c " --"if;'"""TIle Qof aprnnical simpleresonantcircuiTis always lower than that of thecomponcmcoil or cap:u::icof because ofadditional losses in the circuit whichoftcn appear sidual losses.Andify = 0.10, it rnl':lnsofrhe tOtal circuir Joss is not due ro thecoil measured bUl due [Q the internalloss of (he Q Merer. The effective Qshouldthereforebehigherthanthecircuit Qby [he factor11.11I-y 1-0.1TheC C 1-- facror inQ..= -- " Q,CxC, I-yrakes careof theefh>Ct due to residualinductance. \Xlhen frequency and (:1.-pacitancearcchanged, theresultingefk-ct ony, i.e., on(he differencebetweeneffectiveQandcircuit Qcan be easilyestimated fromthe expressionQ,f","y=000114--.'Cp,p,ftogetherwirhthe a 'IS C' graph.111l: 01 to0" correctionrefers toleveleffeer nQt discussed so far. In the260-AQMeter, at a frequency ab!we20 me, the voltmeter loading increasesas thesignal level (i.e., theQreading)decreas100.2. For the190A Q Meter.C3.) Campmc C, frome, =-:---::--::--l-w'L"Cb.) Find{3from{3'15 C' graph(Figure 7)0.OO573QIe.) Compute7j by 7jC/JpJC 1d.) ObtainQ.. by Q..= __ Q,CX1-1)wherethephysical me;lIlingof {3and7jcorrespond respectively to those of 01and y.Outline of derivation of above rcla-tions(forQ Meter) :GI'+R.w'C'y=-=--=---GlwCQ1G1, R,w'C'--(1+--)wC GI,R,w'C'a=---+l, G,.=kf'G1;1Q,.=--R,wCxG1 =G" + Rxw'C'Eliminate R,betw{'{'n Q.. and G,.w'C'C wC. '--C 1=--'---Q,C" l-y100.5 ,u.,u.f301103.11.026101005.700.0026,u.h0.0258C'{3 fromf3vs C'graphI.,. w'r..,CC !-w'I...,C106 CxC,To Ket Q..83804.15Measured data;91.5 p,p,f II C187 QITo get e,:0.015 ,u.h0.1351.160.113C,C l-w'L,.CC,w'l"CCQ,C'afroma. vs C'graphCorrection fora.t 250( --1)3 Q,h:ample: Computationof Q.. frommcasun::ddara of a o.! ,uh Coil ar 50 me.260-AQMetp.r 190-AQMeterc' r..-",- -,ISln"ALLAS ,. r LIPSco"e .. 15OCIATHP.O. e.. 10MT...._, [I ........53.1HE" IIAYEH.C_...., A.I"C.1150,,1>011., ....f.I........ , p 7-61010UN """0 f. C,"'"",llEELYENfUPRISU1019R...".".So T.\.,>-. Ado ... '''''0iGHE5 ._. C''''...I."nllE"l!RPRI5ES.3939 '; ..8..1......N."h 11,... c."'.."I.ToI , S.".I., 7-on,1I0utrO>i. r EARlllP5COl-, (loo.fI.,.4-nOlI6 ALO. H y..,E OIS """AISOC '''C." Go-_.fl.l. A...""............ NowY..To'........ ,f,"'''' 9503RADIOI.!============ JERSEY ============!J8Pdn,.dInU.S.A.Determination Of Metal Film Thickness Anon-destructiveelectronicmethodapplicabletocombinationsof coating and basis materials,at least one of whichmustbe a conductor. Themeasurementofthethickness of thinfilms,oftheorderoflo-"inches orless,hasalwaysbeenoneofthe major problems for the coating industry, whetheritbeaquestionofmetallic filmsonametalbasis(e.g., suchasare producedbyelectroplating) ; or metallic filmsonaninsulator;oraninsulating film on a conducting carrier. Therehasbeenadeeplyfeltneed fora reliable, rapid,simple, non-destruc- tivemethodforobtainingabsoluteor comparativethicknessreadingsonthe majorityoffilm-basiscombinations. Hithertoavailable methodslackone01 moreofthesedesirablecharacteristics. Thicknessmeasurementshavebeen basedonthefollowingmethods: mechanical,chemical,electrochemical, optical,X-rayandbetarayscattering; magnetic, electrical conductance, and last butnotleast,eddy-currentproperties. Description of Available Methods for Measuring Plating Thickness Mechanical:Mechanicalmethodsin- volvingtheuseofamicrometeror similardeviceareusefulinalimited numberofcases:thespecimen ismeas- uredattheidenticalspotbeforeand afterplating.Obviously,theshapeof thespecimen has tobesuitable forsuch a measurement, andthethickness ofthe deposit has to be appreciable. The chemical, electrochemical and op- ticalmethodsaredefinitelydestructive. Chemical: The majorityofthe chemi- calmethodscanbereducedtoade- ~, It YOU WILL ALSOFI ND. . . AMethodofMeasuring FrequencyDeviationPage 5 RFCal i br at i onofthe SweepSignalGenerator Type240-APage 6 Editor's NotePage 7 I 'ANTSPI I P,Deuel opment Engineer Figure 1.The author shown measuring plating thickness of a capacitor frame. terminationoftheweightofcoating metalperunitarea.Theyinvolvethe followingsteps:measurementofarea, strippingtheplatingw*ithareagent thatleavesthebasisunaffected;direct determinationofcoatingmateriallost throughstrippingbymeansofweigh- ingthespecimen.beforeandafter stripping,oradeterminationbyappro- priatequantitativechemicalanalysisor colorimetryoftheamountofcoating materialgoneintosolution.Forrough checks,thedroppingmethodcanbe usedincertaincases:aprescribed strippingreagentismadetodrip under controlled conditionsonthepiecetobe tested, and the time noteduntil the basis becomes exposed. Ektrochemical:Electrochemical plat- ingfhickness measurementisactuallya deplpingoperationofaknownarea. Thenumberofcoulombs(amperesec- onds)requiredto expose the basis metal isameasureoftheamountofmaterial removed,asstatedbyFaraday'selectro- chemicallaw.Thesharpchangei nde- platingcellvoltagethatoccurswhen thebasismetalisintroducedintothe electrolyteisusedasanindicator. Optical:Foropticalmethodsthe specimen ismountedin a clamp orpro- tective medium(usually a thermosetting plastic),slicedaccurately,thecutpol- ished, etched andmeasuredeitherunder amicroscopeokprojectedatknown magnification. X-rayandBetaray:X-rayandbeta raytechniquesrequirequiteelaborate instrumentation.Neitherofthesetwo methodsisnecessarilydestructivefor the specimen to be measured. Thefollowingmethodsareallnon- destructive, and should properly be called comparators,sincenoneofthemis capable ofyielding an absolute measure- mentwithoutrecoursetoprecalibrated standards.Likewise,theyaresensitive to the geometry ofthe specimen. Magnetic:Themagneticmethods obviouslyarelimitedtocombinations whereatleastoneofthecomponents, eit