Kenwood TS-990S Service Manual
Also see for SP-990: Instruction manual
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TS-990S15CIRCUIT DESCRIPTION3-8. IF FilterThe IF filter includes multiple analog filters in addition toa DSP digital filter in the IF stage to have sufficient tolerancefor unnecessary signals (Refer to Table 9).In order to enhance the resistance to the interference dueto nearby strong signals, not only the MCF but also the nar-row bandwidth (500Hz and 270Hz) ladder-type crystal filtersare mounted in the 1st IF (8.248MHz) stage. Any additionalfilter available commercially and attached by a user may bemounted on CN153 to CN155.In FM mode, the ceramic filters (CF1 and CF2) with fre-quency bandwidths of 12kHz and 9kHz are mounted in the2nd IF (455kHz) stage.Table 10 shows the relationship between the types ofDSP fi lters selectable and corresponding roofi ng fi lters.IFBW shows the bandwidth of each roofing filter and isset according to Table 10 while in AUTO mode. Respectivefilters set in the user menu are selected if the default settingsare changed.Fig. 13 Noise blanker filter and IF filter adjustmentsL97/L98XF3/XF4L94/L95CN115From Branking8.248MHzTune connectorCN129To AGC AMP8.248MHzFrom POST AMP8.248MHzL99XF8L96CN115 CN129Tune connectorTune connectorCN86L111XF1NoiseblankerL97XF3L94CN129To AGC AMP8.248MHzTune connectorIF filter circuit(15kHz)D26~29BlankingFilter circuit for noise blanker(15kHz)IF filter circuit(6k/15kHz)From Blanking8.248MHzTune connectorTo AGC AMP8.248MHzTune connectorIF filter circuit(2.7kHz)L110Item XF1, XF3: L71-0677-05 XF4: L71-0676-05 XF8: L71-0675-05Nominal center frequency 8.248MHz 8.248MHz 8.248MHzPass bandwidth ±7.5kHz or more at 3dB ±3kHz or more at 6dB ±1.35kHz or more at 6dBAttenuation bandwidth ±37.5kHz or less at 60dB ±16kHz or less at 60dB ±3.75kHz or less at 60dBRipple 1dB or less 1dB or less 2dB or lessInsertion loss 3dB or less 3dB or less 5dB or lessGuaranteed attenuation 70dB or more at fo±1MHz 70dB or more at fo±1MHz 60dB or more at fo±1MHzCenter frequency deviation Within fo±1000Hz Within fo±500Hz Within fo±200HzTerminating impedance 5.6k//0pF//2pF 2.4k//2pF//15pF 1.35k//7pFTable 9 (1/2) IF filter specifications |
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