TS-900_review_CQ_1975.pdf

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1、Front view of the Kenwood 15-900s.s.b. transceiver.Asmalldooron the leftside of thecabinet concealstheMicGain andVOXGaincontrols.The lever switches below the meterare for Send/ VOX/Receive,NoiseBla nker On/Off, RITOn/Off, Crystal Controlled Channel 1 or 2,and AGC Off/Fast/Slow,The RITcontrol is to t

2、herightofthemain tuningknob.Inthe space a bove the v.f.o. dial canbe seen two of the three illuminated warninglegends: RITand T MUTE. I - - - - - - - .- CQReviews: TheKenwoodT8-90088B Transceiver BYRICHARDA. ROSS,K2MGA FORthepast severalmonthsithasbeenour goodfortune to have theuseofoneofthe Kenwood

3、TS900SSBTransceivers manufac- turedin Japanand importedtothe USAby Henry RadioofCalifornia.Goodfortune in- deed thatthis rock-solid reliable rig wasloaned to us byMarySilvaofHenry Radio without whoseforbearancewemightnothavehad occasion to enjoy the TS-900 for as long as we have. Youmight term this

4、evaluation a one-year-later report since thats how long the 900 has been under the scrutinyofthis reviewer and others. With few exceptions.theTS-900 incorpor- ates asmany desirableoperating and technical features in a single rig as any discriminating amateur could ask: noise blanker, semi-break- in

5、c.w. 500 Hz c.w.filteroption. RIT. FSK provisions. phone patch connections. full meter- ing, crystal control for net operation. 25/100 Hzcalibrator,15MHzVWV reception, full 80-10meteramateurband coverage with all crystals included, dualAGCsystems, selectable AGCspeed, plug-inmodularconstruction and

6、manymoresubtle niceties which continually disclose themselves asonegets to know the rig. Receiver Circuitry Lets beginourtrek through the TS900 with a look at the block diagram,fig.I, which shows a double conversion transceiver. Onreceive. Editor.CQ signal from the antenna isfirst passed through a v

7、ariable attenuatorto a dual gateMOSFET r.f. amplifier and then to the heterodyne mixer, also a dual-gateMOSFET,where it is mixed with theamplifiedoutput of a band-switched crystal controlled oscillator to producethefirsti.f. rangeof8.895to8.395 MHz.For example on 14.000-14.500IHz. the heterodynecrys

8、tal fre- quency is 22.895MHz yielding the 8.895MHz to 8.395MHzdifference frequency range(other heterodyne oscillator frequenciesareshown in fig.I).Theoutputofthe heterodyne mixer is fed to the inputofthe v.f.o. mixer through a band- passfilterand is tunedoverthe8.895to8.395 MHz range by meansofa var

9、icap diode whose applied voltage is varied by a potganged to the v.I.o, In the v.I.o, mixer the amplified v.f.o, out- putof5.500to5.00 MHzissubtractedfromthe first i.f. range to yieldthe3.395MHz second i.f. The3.395MHzsignal is then fedtothe Noise Blankerboardwhere it is filtered and amplified by a

10、dual gateMOSFETandfed to oneofthree diode-switch-selected crystal lat- tice filters for u.s.b., I.s.b,orc.w,Twodual gateMOSFETi.f.stages follow thefilters and feed the 4-diode balanced mixer. The carrier oscillator (common to bothtransmit and re- ceive)usesdiode-switch selectionofthe de- siredcarrie

11、rcrystal:3394.15kHzforc.w., 3395kHzfors.s.b. 3397.125 kHzforFSK Space(ontransmit.Markis accomplished by diode-switching a short across two small capa- 24CQFebruary,1975 IT 2 -. . n c . - 1 Fig. l-Block diagram of theKenwoodT5-9oos.s.b.zc.w. transceiver. II 1M t6R,F.AGe AF.,AFPOIiI- R F. AGe .,-.phi.

12、,mph!; I II 2S/1O(),HIBulf_ R F. AGeR.F. AGe Drill., U. AF hbr.1Ot.plol. do , mplil.controlLSBpr.,-,p 3396S5IoH, r-e- AII.IOI R F.H,t.VFO BlanIin;USB - B.1.del amplol., m i. m,mphh.,.3395,45HI.mplll. - AGe AGe - No;.AGe cw AGe -pl,l.rnplll,. 338SlH, buff., Sidot 10-. , .,mp .1 .U,l Bull.,Bull. mplot

13、,.Schmll ,mphl,.,mphl., Buffer ,- AGeAOII-YOM f tlCt .,mphfl4f H.CVII,1Bulteor S11If ote,U.IQI011:,111101.plol. Buffer Some,. L. .,1Il.,mphl., CD AGe Amph., .mphl. C. C oror VFO OS5MHI SO55MHI 338SlH, 0.* Buff. Or ,mph.ote,UlOt P,IWOfk PA . HVFO IIIlIYIJroG 2-6L06 BOK m,. mI. ,mp, - MIC,;.;-,n 8.18n

14、MICrophoneMaophone MIC ALe .mplili.moduliiOt.mph . , pt.,mp. mplll ALem.ler Buller MelM - ALe .mplil,.mphf;. :. - *HlPt.otr:.lIorcrllrequlrnl; T RII WWV - 2389S R.h. S.ltclli9 Ool.yvox I- Sidelone . 7B.0-36 relay 3S-17.39S78.S-37,m :J t:Ofllrolconuol ,mphl.OICitialOf 70- IS.B9S790- 37B9S 140-nB9SN,S

15、-3B,95 .J210-N89S black r.f. onal NoiseBlanker TheTS900noise blankeruses abalanced gate arrangementtoopenthe 3.4MHz signalpathfor theduration of a noise pulse.Broadband 3.4 MHzi.f.input from the v.f.o, mixer is first fed through ahalf-latticecrystal filter having aband- widthofabout 10kHz to restric

16、t blankeropera- tion to noise pulses in close proximity to the tunedfrequency. A two-stage IC amplifier taking signal fromthe filteroutputis controlledbya relatively slow-attack a.g.c, system which allows the fast-rise-time noise pulses to be amplified before the a.g.c, begins toact.These pulsesare

17、then shaped and drive aShmitttriggerwhich biases the gating diodes offforthedurationof the noise pulse. Inoperationthe blankeris ex- tremely effective on impulse noise, thoughwhere the pulse noise levelis low its effectiveness diminishes. an a.g.c, voltage,andapplies thecontrol volt- agetothesamegat

18、eofther.f.amplifier MOSFETas theconventional a.g.c.Theconven- tional a.g.c, voltage is applied through a steer- ing diode. Theaction is as follows:A strong signal within the receiver passband activates the reg- ulara.g.c, loop.Ther.f. a.g,c. is inactive if no strong signal is presentoutsidethepassba

19、nd. Ifa strong signalappears outside the passband, thenormal a.g.c, loop will notseeit,butthe r.f. a.g.c, will sinceitsamples signalbefore i.f,selectivity is introduced.Ther.f. a.g.c, thus reducesthegainofther.f, amplifier, prevent- ingoverloadorintermodulation. A signallamponthefront panel lights w

20、hen the r.f. a.g.c. is workingbutextinguishes when the very strong off-frequency signal is actually ,tuned in.This occurs because as thestrong signal enters thei.f,passband, it is seenby theconventional a.g.c, which intumreduces the gainofther.f. amplifier. Sincethesignal then reachingther.f, a.g.c,

21、loopis then re- duced below itsoperating threshold.ther.f. a.g.c, is disabled,andthewarninglampextin- guishes.Rf.a.g.c, voltage is preventedfrom reaching thei.f.stagesthrough theconventionaJ a.g.c, line because of the steeringorblocking diode. Seefigure 2. R.F. htmixer . VFOCrystalIF Det. amplifierI

22、.mixerfiltersamplifier a GI G, h S LocalConventional VFO oscillatorAGe Fig.2-Simplified A.F. AGC diagram showingthe :.: a.g.c.andconventi c.a.e. systems. AGeSystems Twoindependenta.g.c. systems are incorpor- atedin theTS-900. Aconventional system picks upsignal voltage from theoutputofthe sec- ondi.

23、f.amplifier, amplifying and detecting it and applying the amplified a.g.c. signal to the second i.f. string and r.f. amplifier. Should a strong signal bepresentoutside the receiversi.f.passband, strong enough tocause overload of ther.t. amplifierorintermodula- tion, a seconda.g.c. system is activate

24、d.This system, calledRFAGC, samples signal at theoutputofthebandpass filter preceding the v.f.o.mixer, detectsandamplifiesitto provide Broadband 8.88.4MH, Signal input citors in series with theFSKcrystal). Audio outputfromthe balancedmixer is fed to the audioamplifier string whichincludes alow pass

25、filtertoshape the audio response; the 8ohmspeakeroutputistransformerless using acomplimentarypairofpowertransistors. 600 ohmoutputforphonepatchoperation is pro- videdthroughan 8ohmto600ohmtransform- erfromthe 8ohmspeaker line. For in-circuit testingof circuit modules thePC boardsareunpluggedfromthei

26、r sockets,the socketsarehingedoutfrom the bottom of the rig, andthePC boa rdsarere-inserted. Steeri diod 26COFebruary, 1975 , TransmitterCircuitry Thetransmitter is quite conventional in most respects. On s.s.b.aJFETprovides high imped- ancemic inputandis followedbytwo bipolar pre-amp stageswhichpro

27、vide audiotothe 4- diode balancedmodulator.Carrier is provided bythesamecarrieroscillator asonreceive. Thebalancedmodulatoroutputdrives a MOSFETi.f,amplifierwhichis a.l.c. controlled. The3395kHzd.s.b. signalfromthei.f,ampli- fier feeds the diode-selectedcrystal-lattice filters which produceans.s.b.

28、signal. C.w.operationisaccomplishedbyunbalanc- ingthebalanced modulatorbyapplyinga d.c, bias through acarrier level adjustpot.Micpre- ampcircuits are disabled. Keying is achieved bykeyingthesidetone oscillator whose output operates the VOX circuit. Sidetone is also ap- plied througha level control t

29、o the receiver audio section formonitoring. Theremainderofthetransmittercircuitry is straightforward;astageofi.f. amplification afterthe filters.v.f.o.mixerproducing 8.895- 8.395MHz signal output which is mixedagain with the heterodyne oscillatoroutput to yield the operating frequency.Output fromthe

30、 heter- odyne mixerdrives a6GK6whichinturn drives a pairof6LQ6s in parallel as power amplifiers. A.I.c. isofthe amplified type withthe a.l.c. amplifier sampling PA grid currentamplifying and applying corrective biastothe twotrans- mitteri.f.amplifiers.A.l.c.voltageisalso amplified andmeteredas an in

31、dication ofcor- rectorexcessive mic gainandalso fordriver tuningadjustment. Afewwords aboutthe installationof the optional500Hz c.w.filter: As delivered the TS-900uses theuppersideband filterforu.s.b. andc.w. onbothtransmit and receive though onc.w,the 3394.15kHzcarrier crystal is used fortransmit a

32、nd 3395kHzfor receiver b.f.o., meaningthatthedial pointerwill indicate 850 Hzlowerthanthe actual received andtrans- mitted frequency. Whentheoptionalc.w,filter is used these twocrystalsarereversed (3394.15 kHz b.f.o.; 3395kHzcarrier) meaningthatthe receivedandtransmitted frequenciescoincide with the

33、 dialpointer.This reversing is accom- plished by unplugging. reversing andre-plugging aflat6-conductor plugandsocketunderthe chassis at the timeofinstallationofthec.w, filter. Metering In additionto the a.l.c. metering mentioned previously afrontpanel switch permits reading PA platecurrent.r.f.outpu

34、t(relative),andPA plate voltage.Onreceive, themeterautomatic- ally reads signal strength. PA platecurrentis measured by reading the voltagedropacross 1ohmPAcathoderesistors and amplifying this voltage which is thenread by the meter. Close-up ofthedriverandPAcompartments, viewed fromthetop.Rightangle

35、gearsdrive variablecapacitors for receiverd .amplifierand transmitterdriver tuning. At the center, the chain/ sprocket drive for thePAloading is visible. R.f. output is measured through a voltage divideracross the 50 ohmtransmitter output, and detected by a diode. PA plate voltage is readacross a vo

36、ltage divideratthePA a-plus feed point. RITandIndicatorLights Receiver incremental tuning isaccomplished by applyingandvarying the bias on avaricap diodeparallelingthe v.f.o. tuningcapacitor. Thediode is alwaysconnected,butis biased only whenthefrontpanelRIT switch is en- gagedandthetransceiveris in

37、thereceive mode.WhentheRITswitch is engaged,awarn- ing legendRlTilluminates in the space above the tuning dial andremains on untiltheswitch is disengaged. Onthe frontpanel RITcontrolpot(which has a tuningrangeof2 kHzapprox.) is an- otherswitch at the full counterclockwise posi- tionwhich disables pl

38、etelyand energizesacrystalcontrolled oscillator in its place. Two crystals in the 5.0-5.5MHzrange maybe inserted in sockets provided internally andselected byafrontpanel switch fornet operation or other purposes requiringprecisely repeatable frequencies.Theilluminatedv.f.o. dial pointer extinguishes

39、 when crystalcontrol is used. Otherlighted legends also appearabove the v.f.o. dial: the RFAGewarning lightanda T MUTE light indicatingthat thedriverand PAfilaments areswitched off by theirfront panel switchasthey might well be when just monitoring the bands. Construction This reviewertakes particul

40、ardelightin fine mechanical devices in addition to fine electronic devices.Forthisreasonamongothers.the KenwoodTS-900 hasbeen a pleasantreviewto February, 1975CQ27 RearviewoftheT5-9ooshows avarietyofcon- nectors:speakerandphonepotchatupperright, relay contactsande.l,e. below. Right to leftalong the

41、bottomare:groundpost,externalv.f.e. con- nector,powerconnector,Rmandc.w. key jacks, 50-239antennaconnector,antennaselector switch, receiver-onlyantennajack,andanother groundpost. Above the keyandpower connec- torsareslideswitches forPAscreen supplyon/off, andremote/internolv.f.o. At thetopcenterad-

42、jacent to the fanoreadjustments forPAbias,d. voltmeter,andanti-vox. write.TheTS-900 is a well-constructed, well- thought-outandsmoothly functioning pieceof equipment. Thepackagemeasures12% wideX5y highX12%deep and weighs a little over 26 pounds.Thefrontpanel is satin-finished extrudedaluminumwithmou

43、ldedsatin black high-impactplasticescutcheonsforthedial andS-Meter,andforabankoffivelever switches.Thecabinetis steel, finished in a rug- gedblacktexturedpaint,andis designedfor severaldegreesofaccess to the interior. A re- movablehingedtoplid is secured by snap fasteners. (and a single screw forshi

44、pping or transporting). and allows access tomost intern- al adjustments. Formore extensive work top- side.removal of seven screws allows the top portionofthe cabinet10beswung aside on split butthinges.Removalofseveral more screws removes the cabinet bottom. TheTS-900 is largelymodularin itscon- stru

45、ction.withmost circuitryonPCboards which plug into high qualityPCedge connec- tors.Theseboardsareclosely packed. but well shieldedfromeach otheraseach fits into its ownmetalcompartment.Service is facil itated by a swingoutarrangementon the PCboard connectorspermittingtheboard to be removed. theconne

46、ctorswungoutfrom thebottom of the set. and theboardreinserted in theconnec- tor.Thus access is available toboth sides of theboardwhiletheset is live. Inadditiontotheshieldcompartments for boards. several topshieldscovervarious com- partments, and also identify theboards and theirassociatedadjustment

47、s.themostcom- monly usedofwhichareaccessiblethrough holes in the shields. ThePAisconventionallywiredanda per- manently installed partofthe structure. Driver tuningis accomplishedbymeansofseveral unusually small multi-gang variablecapacitors which are ganged by meansofnylon bevel gearstomatinggearson

48、thedrivertuning shaft. PA loading is concentrically locatedon the PA tuning control shaft,andthe loading capacitoris drivenbyaruggedchainand sprocketarrangement.Operationofthesecon- trols is smoothandverypositive,particularly in viewofthequantityofmechanicaldevices involved. V.f.o. tuning isvery lig

49、ht,butwithadjust- able weighing.Themachined black anodized aluminumtuningknobis quiteheavyandgives excellentflywheel type tuning along with great smoothness.Thelargeknobisoneofthebet- terones in usetodayonanyamateurtrans- ceiver, A3dia.shieldedfan-typebloweris mountedattherearofthePAcompartment forcooling.Unfortunatelythenoiselevel fromthefan isratherhighandthe fanruns continuously as longasthepowerswitch ison evenifthedriverandPAfilamentsarenot powered.something wefoundannoying. Thebands