Marconi atalanta_manual_v6 电路图.pdf

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1、, I , . MARINE -I RADIOAND ELECTRONIC I r; t j EQUIPMENT i ; 1 1 ATALANTA RECEIVER TYPE2207C by F. C. MAYOH, B.E.M. (lst ClassP.M.G. Certificate) and G. L. DANIELSONM.Se. Tech., D.Se., A.M.I.E.E. (lst ClassP.M.G. Certificate) Handbook Re!R (S) 37. =;- - - . RadioFans.CN 收音机爱 好者资料库 ,. * ( Marconi Mar

2、ineAtalanta receiver (Type 2207c) - -.- 0 0 iJ . 0 iJ , , :1. RI32 , , , ,.jf , , 11 CI37 R46 IRI09 I CI23 R40 Jr-1: -:-:r: R39R37 CII9:r: -I R26 R33 RI08 R29 CII3 :r: -=CI23 -IIR36 R39 R37 CI38 MR3MR4 re a:CII6 R41 CI48 MR6 RS9 R80 CI4S - - -.- - - RCUIT DIAGRAM OF ATALANTAMARINE RECEIVER R96 R64 R

3、I36 CI49 CI90 :r: :r -:- CI47 11L59. RS8 :r: R66R6S CI41 CI73 MRS Rn r- a: CIS4 CIS7CS9 -LL 82 GRID DESENSITISING. R69 CIS2 7 R73 1176 C 155 . . I IISV I T r- CD a: R89 IT FIG. I V6 V7 VS V9 VI3 VII OL2R84 PLI GENERALDESCRIPTION Section1 1.1BlockDiagrams Section1.2givesdetailsofthefrequenciescovered

4、byeach ofthetenrangesofthereceiverandoftheintermediatefre- quenciesemployed.Blockdiagramsofthereceiver,appropriateto thevariouswave-ranges,areshownin Figs.2, 3 and4 andshould helpthereaderkeepin mindtheoverallpicturewhilestudying theexplanationsoftheindividualcircuits. RAIICTE, A.G,G.LINE f1Cr.2 rT

5、V3 v RANC1ES 3, 4I V8. - - - D77 or EB91 - - - double diode. V9. - ECH81 orX719 - triode heptode. V10-B309 or 6060-double triode. Vll- - -N37. - power pentode. V12- - QS75/20 - voltage stabiliser. V13-Z77 - pentode. V14-ECH81 or X719 - triode heptode. (optional fitting) COARSE LOGGINGSCALEFINE LOGGI

6、NG SCALE A.G.C.thiscanbeseenfromthefollowingtablewhich showsthattherequiredsignalfrequencychangeis morethanthree timesthecorrespondingoscillatorfrequencychange. Signalfrequency Osc.frequency LF.=700 kc/s 25-100 kc/s 725-800 kc/s f max/fmin=4 / .=1.1 f maxf mln Forthiswave-range,therefore,thesignalfr

7、equencycircuits areuntunedandconsistofanuntunedtransformerinputwithhigh andlowpassfiltersresultingin a broadbandR.F.circuitcover- ing the wholerange25 kC/sto 100kc/so Frequencyselectioninthisrangeis providedsolelybythe manualtuningof theoscillator. Inordertorenderthegainofthereceiverasconstantas pos

8、sible,overthewidefrequencyrangecovered,(15 kc/sto28 MC/s),asmallamountofnegativefeedbackisappliedtothe inputsof Vland V2byleavingresistorsR35and R23 in thecathode circuitsun-bypassed. 5 2.2Calibrating Oscillator (V13) This circuit oscillates at 700 kc/s and, owing to the need for extremefrequency st

9、ability, is crystal controlled.In order to provide an output rich in harmonics, electron coupling is employed; by this means amplecalibratingsignalis obtainedeven at fre- quenciesrequiringthe use of a high order of harmonicfrom the calibrator,in fact up to 28 Mc/s,the upperfrequency limit of therece

10、iver. RC2 x c, x FG.9 FIG.10 Figures9,10 and11showthedevelopmentoftheoscillator fromthestandardPiercetype(Fig.9),throughtheinvertedPierce type(Fig.10)inwhichtheoutputmaybetakenfromanodeor cathode,to theactualcircuitemployedin thereceiver(Fig.11). HerethecapacitorsC161,C162andC163forma potentialdivid

11、er betweenthe crystaland the valve,resistorR88(150 k ohms)provides a conductivepathfor C161whichis otherwiseisolated,whileR60 withC162providesgridbiasforthevalve.R91,of 47ohms,is a gridstopper. Theoutputfromthe anode is takenby a longleadwhichpasses closetotheoutputandinputcircuitsof V3beforeearthin

12、gvia C95,sothatsignalsatcalibratorfrequencyanditsharmonics appearin bothcircuits. 2.3 calibratingAction Switchingthe receiverto Calibrateresultsin:- (a)TheapplicationofH.T.tothecalibratoroscillator (Cal.Osc.)V13. (b) Theremovalof H.T.from VIand V2to preventtherecep- tion of external signals-unlessex

13、ceptionallystrong. 6 (c) Theremovalof H.T.fromtheB.F.O.fora reasonwhich willsoonbecomeclear. TheswitchingofthedetectortoPhoneoperation(see Section6.2). (d) x c R93 R88 FIG. Thereceiveris tunedto theregionin whichitis desiredto effectcalibration,sayabout4 MC/s.At4.2MC/sonthetuning scalea goodsignalsh

14、ouldbedevelopedatthegridof V3fromthe sixthharmonicofthecalibratoroscillatorandthiswillbeat withthe4.9MC/snowbeinggeneratedin thelocaloscillatorto create an output from V3 at about 700 kC/s(4.9 MC/s-4.2MC/s); howclosethisfrequencyis to700 kc/sdependsontheaccuracyof thereceivertuningscale.Alsointheout

15、putisa voltageat exactly700 kc/s,thisbeingcoupleddirectlyfromthecalibrator oscillator(viathelongleadreferredtoin Section2.2).These twofrequenciesareamplifiedandbytheactionofthelocal oscillatorassociatedwithV5arechangedtofrequencieso, respectively,approximately85 kC/sand,exactly85 kC/soBecause theB.F

16、.O.hasbeenswitchedoffbytheactionofthecalibrator switchthesetwofrequenciesaloneappearattheinputtothe detectorwheretheybeattoproducea noteatthedifferencefre- quency.If thereceiveris nowtunedtozerobeati.e.to exactly 4.2 Mc/sin ourexample,thescalereadingmaynowbechecked;if itis accurateit will,ofcourse,r

17、eadexactly4.2MC/s. Theprocesscanbecarriedoutatanyfrequencywhich multipleof700kc/s(in theR.F.bands)anditcanalsobe tosetupthereceiverforbandspreadinginthesixmarine bandsas describedin the manufacturersmanual. is a used H.F. 7 7. FREQUENCYCHANGING Section3 3.1Frequency Changers (V3, V4 and V5) Two inte

18、rmediate frequencies are used, the tuned circuits of the oscillator(V4) beingarrangedto producethe appropriate frequency,fo, asshownin the table below;fs is thesignal frequency. fo=fs + 85 kc/s fo=fs+700kC/s fo=fs+700kc/s 2 RANGES1,3,4and5 RANGES2,6,7,8 andg RANGE10 On range10,thesecondharmonicof th

19、eoscillatoris employed so that the maximLLm oscillatorfrequencynecessaryis about15 MC/s insteadof about30 MC/sas wouldotherwisebethecase;frequency stabilityisthereforeimproved.Radiationeffectsduetothe localoscillatorwillalsobereducedsincethesignalcircuits aretunedto a differentfrequencythantheoscill

20、ator;alsothe possibilityoftheoscillatorbeingpulledwhiletuningthesignal circuitsis minimised. ThetriodesectionofV3(Fig.1),isnotemployedinthe localoscillatorcircuit,insteada separatevalve, V4, is usedfor thispurpose;thisresultsin bettersignal/noiseratioandalso in improvedfrequencystability. Cl0l,in sh

21、untwithCgg,thetuningcapacitorofV4,isfor temperaturecompensation,thus further improvingfrequencystabili ty. Theinputtothesecondfrequencychanger,V5,is alwaysat 700 kc/sso thattheoscillatordoesnotneedto betunableovera widerange;it is,in fact,basicallyafixedfrequencyoscillator tunedto615kc/s,buta smallv

22、ariablecapacitor,Cl03in Fig.1, providesforavariationof:t 3 kc/sonallfrequencieswhich employ this intermediatefrequencyso thatfinetuning is available; underconditionsofinterferencethisisanexceedinglyuseful facility.AtV5thesignalisfairlylargeandthefrequency relativelylow;thereis,therefore,no needto em

23、ploya separate oscillatortoimproveeitherstabilityorsignal/noiseratio:in thiscase,accordingly,thetriodesectionisemployedasthe localoscillatorvalve. 9 8 .- INTERMEDIATEFREQUENCY Section4 4.1I.F. stages (V6. V7) V6is thefirstintermediatefrequencyampli fierand has simple A.G.C. together with manual gain

24、 control (Fig. 12). V7 has neither A.G.C. nor manual gain control. I05V. VI CI05 CIOO FIGr.12. RV2is aninverseloglawpotentiometerwhichprovidesbias fortheR.F.valves;RV3is a loglawpotentiometerbymeansof whichthebiasonthefirstI.F.amplifierV6canbevaried.The twopotentiometersaregangedtogetherandformtheR.

25、F.gain control. Itis interestingto notethattheresistorsR2,R6,andR28 (see Fig.1) whichprovidestandingcathodebiasfor VI,V2and V6 are mostessential,for whenthe R.F.gaincontrolis at a maximum andtheA.G.C.isswitchedoff,theyprovidetheonlybiason thesevalves. Otherthingsbeingequal,the narrowerthe bandwidtht

26、he higher the gain of the receiver.In order to render the overall gain as constant as possiblethe circuit providesfor the inclu- sion of an additional cathode bias resistor for V7 when operating in the INTERMEDIATE and NARROWpositionsthus reducingthe gain 9 of this valveand so counteractingthe gener

27、altendencyof the gain to increase:this is arrangedby ensuringthat the switch acrossR2is thenopen.In the WIDEpositiontheswitchis closed thus shorting out R32 and increasing the gain of V7.The next Section, and also Appendix 1, refer to the filter employed to obtain VERY NARROW bandwidth;to minimise a

28、s much as possible any changein overall gainin this case V7 must be in its mostsen- sitive condition and R32 is again shorted. 4.2VariableSelectivity Fourvaluesofselectivity WIDE INTERMEDIATE NARROW VERYNARROW areprovided: - - - 8 kc/so - - - 3 kC/so - - - 1 kC/so - - - 100c/s. On the lowfrequencyra

29、nges,1 and 2, the WIDEandINTERMEDIATE positionsoftheselectivityswitchareshortedoutleavingthe receiverintheNARROWposition. Teselectivityswitcheffectsitscontrolinallbutthe VERYNARROWpositionbyvaryingthecouplingbetweentheprimaries andsecondariesoftheI.F.transformers.Thisis arrangedby meansofswitchedmut

30、uallyinductivewindingsconnectedinseries withtherespectivesecondaries.Forthe VERYNARROWpositionthe magnetostrictivefilter is broughtintooperation(see Appendix1). The700kc/sLF.transformerhas two passbandsonly;14 kc/s intheWIDEandINTERlVIEDIATE, and8 kc/sintheNARROWandVERY NARROWpositionsoftheselectivi

31、tyswitch.Thisenablesthefine tuningcontrolCI03(Fig.1)in the oscillatorcircuitof V5to be used(see Section3.1). The85 kc/s LF.transformershave threeselectivitypositions: 8 kC/s,3 kC/sand1 kC/sas above. 10 DESENSITISINGANDMUTING Section5 5.1 RelayDesensitising -Z4-v.+ 1 8c - -r- RL I LB I - FIG. 13 Refe

32、rto Fig.land Fig.13. Withkeyup,RLA/landRLB/lareshort-circuitedbytheback contactsofthekeyandthe24voltsisentirelydroppedbythe resistorR,locatedintheAutokey,wherethe24voltsisob- tained.Whenthekeyisdown,RLA/landRLB/lareenergisedby the 24 voltsupplythroughR.In thiscondition,RLAlearthsthe aerialthroughR5(

33、Fig. 1)anddisconnectsitfromthereceiver. AtthesametimeRLBlopens,puttingRI06(seealsoFig.12)in series withRV2andRV3:this causesthecathodesof VI,V2and V6 to bedrivenso positivebythevoltagedroppedacrossRI06,that theycut off. Inthiswaythereceiverisisolatedandprotectedfromthe signalsbeingtransmitted. 5.2 C

34、athodeDesensitising When no 24 voltsupplyis availableto operaterelaysRLA and RLB, the system shownin Fig.14can be employed.Withthe desensitisinglinkopentheresistorRI06is short-circuited throughthe backcontactsofthe key whenthe keyis up.On pressingthe key, RI06is broughtinto circuitin serieswith pote

35、ntiometers RV2 and RV3, causing VI, V2 and V6 to cut off due to the rise in their cathode potential. 11 HT+ RIo; fIG.4. 5.3GridDesensitising KEY F Anegativevoltageof 40to 50 volts,derivedfromthetrans- mitterfinalstagegrid,is appliedtothereceiverA.G.C.lineas shownin Fig.15,whenVoiceOperatedCarrier(V.

36、O.C.)is employed. TRANSMITTER VIv?. I- I I I I I- - AGe m/OFF FrCr.15 12 FINAtSTAC,E - -j I I I I _J -40VOLTS APPRoX. - - -=- 9727 Theuse of rectifiersMR1and MR2enablesthe A.G.C.and v.a.c.desensitisingvoltagesto operateindependentlyandto allowthelargervoltageto overrideand beoperativeon the A.a.C.li

37、ne. Thefilter R82,C157 and C159in the v.a.c.desensitising line, unlike the A.G.C. rectifier filter, has a short time constant so that the desensitisingvoltagecan operate on the controlled valves veryquickly, whilstthe applicationand decay of A.G.C. voltage is much slower. 5.4MutingCircuit The receiv

38、er has beendesignedto allow the inclusion of a muting circuit which reduces the gain of the receiver by about 20 dEs,()when tuning between stations and (b) when the carrier of the station to which the receiver is tuned is removed;as happens for instance, when tuned to an area or coast stationin betw

39、een the transmissionsof the station.In these two sets of circum- stances a receiver not fitted with a mutingcircuit operatesat a veryhighlevelof gain,the A.G.C.voltageshavingfallen g -L) V=:-.G2OlLMR7 RII;z. VIO(b) Rrso RII3 FIG. 16 drasticallyowingto theabsenceof a signal(see Section6.3),so thatthe

40、noiselevelis veryhigh.Theprovisionofthemuting facilitymeansthatthe operationsoftuningand monitoringcanbe carriedoutwitha quietbackground,afacilitywhichis alwaysof greatconvenienceandin a busystation. canbeof muchimportance. 13 5. L 1Underno-signalconditions:V14(a)is cut-off and its arndeis,therefore

41、,veryposi ti vethusholdingthegridofV14 (b) positive.Thiscauses(V14(b) to conductheavilyand energise RLC/lwhichis in its anodecircuit;as a resultcontact RLCl closes, placing R157in shunt with Rl13in the input circuit to the A.F. amplifierV10(b).Since the value of R157 is less than 10 per cent of that

42、 of Rl13it willbe seenthatthis causesa veryconsiderablefall in theinput to V10(b)andthus brings about the 20 dB reduction referred to. 5.4.2Inthepresenceofasignal:MR7 rectifies the signal from the LF.amplifierV7producingapositive-goingoutputwhich causesV14(a)toconduct,creating a drop in its anode po

43、tential andinthegridpotentialof V14(b).V14(b)cutsoff,RLC/lis de-energisedandthecontactsRLClopen,thusremovingtheshunt resistanceR157andallowingthefullA.F.inputto beappliedto V10(b) . 14 .- DETECTOR,NOISELIMITERANDA.G.C.CIRCUITS Section6 6.1Beat Frequency Oscillator,(V9) Atriodeoscillatorhavinganodeci

44、rcuitsfixedtunedto86 kC/sisfollowedbya heptode,in thesameglassenvelope,acting asanisolatingamplifier.Theoutputis developedacrossresistor R38andinjectedintothebalanceddemodulatorat thecentretapof thelastI.F.transformersecondary.Injectionin.thismanner, withthe veryminimumofcouplingbetweentheB.F.O.andt

45、heI.F. amplifier,virtuallypreventspullingofthe B.F.O. AnyharmonicsgeneratedbytheB.F.O.aremostlyby-passedto earthbytherelativelylowreactanceofC124atthesehigher frequencies,(Fig. 1).At86kC/sthereactanceisabout8,500 ohms-C124 has a capacitance of 220 pF-and at the higher harmonic frequenciesthisvalueof

46、 reactanceis progressivelyreduced.The possibilityofthecreationofanyunwantedspuriousbeatnotes, whichmightotherwisebecontributedto bytheharmonics,is thus largelyavoided. 6.2BalancedDemodulator /.F. IPo B.F:C /V - 1) HT;- 105 V. IT To B.F:O. f PHory.I cf(l.SWH 1- cw. I v - G FIG. ZS Fortheconditionssho

47、wnin Fig.29,forinstance,theoutput voltageis V4-V3 2 = 2-6 2 = -2 meaning that X is2volts negative to Y. If the6 voltand2 voltbatterieswereinterchangedtheout- put voltagewouldbecome 727 6-2 2 meaning that X is 2 volts positive toY. = 2 31 1 L - . -, -y =r:t-A -21 D )(y -00-L OUTPuT - F,29 Thusthe mag

48、nitudeof theoutputvoltageanditspolarityde- pendsontherelativebatteryvoltages.Theoutputis zerowhen thebatteryvoltagesareequal. Nowletthebatteries,whichwereintroducedin ordertosim- plifythediscussion,be replacedbythediodeloads(R andR1in Fig.26),acrosswhichdevelopthevoltagesV3and V4.Theoutput from the

49、circuit will be zero when V3= V4,i.e. whentheinputto diodeD1equalsthattodiodeD2.Sincethecircuitis balanced thiswillalwaysbethecasewhenthe B.F.O.is deliveringnoout- put;forthisreasonin theAtalantareceiveroneofthediodes isswitchedoutofcircuitwhenphonereceptionisrequired. Foranoutputto beobtained,thetwodiodesmusthavedif- ferentinputvoltages;thisis achievedbyintroducingtheB.F.O. outputbetweenthecentretapofthecoilABandearth.Thisis indicatedinFig.30in whichthetwodiodecircuitsareshown separatelyin orderto makeit cl