Kenwood TS-950S Service Manual

Also see for TS-950S Digital: Instruction manual Instruction manual Instruction manual Instruction manual Service manual

TS-9505/SD60CIRCUIT DESCRIPTIONFunctionsThe LPF is a 5th order programmable Chebshevdesign.. It allows the cut-off frequencies to be changedin four steps and the ripple in the band to be selectedbetween 0.01 dB and 1.6 dB. When the ripple is setfor 0.01 dB, the group delay characteristics are pri-mary, i.e., the sound quality is considered to be themost important. When the ripple is set for 1.6 dB, thetransition band characteristics are primary, i.e., theband width is considered to be the most important.The DSP-10 uses two 5th order phase shifters, eachconsisting of five all-range passing-type phase shiftersconnected vertically to obtain sideband suppressioncharacteristics of 70 dB or more. To further improvethe sideband suppression characteristics, the degreeof phase shift is increased or the 90-degree bandwidthof the phase shifter is narrowed.Increasing the degree of the phase shifter is notdesirable because the group delay characteristics de-eriorate and faster processing is required. The DSP-10 implements the optimum characteristics for eachransmit band by changing the design band ratio andfrequency of the phase shifter by a combination of ahigh-pass filter and a !ow-pass filter.Table 15 lists the various of high-pass filters andow-pass filters combinations which are selected toimprove the sideband suppression ratio when the band-width is narrow.Theoretically, there is no carrier leakage by the digi-al multiplier. However, it does occurs due to theoffset voltage that is generated by the noise producedin the processing of the phase shifter. To prevent this,the DSP-10 uses a digital comb-type filter to suppresscarriers. Whenever MIC input is present, this filtermakes the carrier leakage below measurable levels.The cut-off of the high-pass filter for suppressingthe leakage on the opposite sideband of the phaseshifter is the overall cut-off of the analog high-passfilter and comb-type filter.HPF LPF | Phase shifter band110 | 2600, 2750 | 60~3435Hz/700B2900, 3100 | 75~4296Hz/70d8200 | 2600, 2750 | 129~3696Hz/74dB2900, 3100 | 75~4296Hz/70dB300 | 2600, 2750 | 190~5423Hz/74dB2900, 3100400 | 2600, 2750 | 220-6303Hz/74dB2900, 3100NoteThe bandwidth of the phase shifter are thosebefore quantization, and therefore do notexactly match the actual bandwidths.Table 152) CWThe 455-kHz carrier is generated or stopped accord-ing to the data supplied by the keying device. TheOSP detects the leading edge (KEY down) and trailingedge (KEY up) of the keying signal, reads data from theinternal square cosine characteristics ROM, modulatesthe amplitude according to the data, and obtains theshaped CW output.A filter with square/cosine characteristics is used toshape the waveform for data communication. Thefilter has the advantage that it reduces the question-able status (0 or 1) at the data change point caused byovershooting of waveforms, and decreases the band-width caused by data change.Itisdifficultforananalogfilterwiththesecharacter-isticstonameequivalentamplitudecharacteristics,anditmusthavelinearphase. Therefore,itcanhaveonlyapproximatecharacteristics.Inaddition,thisfilterisverycomplicated.TheDSP-10providesgoodtrans-mitwaveforms,inwhicheven steepCWwaveformshavenoKEYclicks,without havingtoresorttotheuseofanalogfilters.WhentheCWspectrumoftheDSP-10isviewedwithaspectrumanalyzer,thespectrumisconcen-tratedatthecarrier.Sincethetransmissionbandwidthisnarrow,thereislessinfluenceevenwhenthere-ceiverpassessignalsthroughanarrow-bandfilter thanbefore.TheCWleadingedgecharacteristicisnormally2msec. Theoperatorcan selectfromseveralvaluesbetween2msecand 4msec..189KHte 49. iedkHz FeRising/falling timeKEYoraEdge detection/shapingData ROMFig.52.CWblockdiagramSin WetFOR SERVICEMANUALSCONTACT:MAURITRON TECHNICAL SERVICESwww.mauritron.co.ukTEL01844-351694FAX: 01844-352554