Kenwood TS-990S Service Manual
Also see for SP-990: Instruction manual
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TS-990S12CIRCUIT DESCRIPTIONIF frequency IF filterModeFM AM SSB FSK CW8.248MHz15kHz *1 *1 *16kHz *1 *12.7kHz *1500Hz *1270Hz *1*1 : manually selectable3-3. From the 2nd IF to the MRIF outputIn FM mode, the signal passing through D30 is applied tothe FM IC (IC9) via D31. In modes other than FM, the signalpassing through D30 is input to the AM/SSB/CW/FSK/PSKmode mixer (D32 and D33) via D31 (Refer to Fig. 7).In FM mode, the FM signal is mixed with the MLO2(7.793MHz) output in the FM wave detecting IC and con-verted into the 2nd IF (455kHz). The 2nd IF signal passesthrough the ceramic filters (CF1: 9kHz (narrow) and CF2:Table 6 Selecting an IF filter3-4. Preselector circuitThis transceiver has a preselector on the PRESEL unit(X42-343 B/10). This function can be turned ON and OFFwith a panel switch.The preselector forms narrow band-pass filters in whichinductors and capacitors are switched with relays for respec-tive amateur bands. (Refer to Table 7.)The filters cause an insertion loss of about 10 dB by theband if the preselector function is used. This insertion loss iscompensated with the combined use of the variable attenua-tor (ATT) in the PRESEL unit and the preselector AMP (Q10and Q11) in the RX unit (X55-313 A/2).12kHz (wide)), is demodulated into audio signals and ampli-fi ed by the FM AF AMP (IC12).Signals other than FM mode are mixed in the AM/SSB/CW/FSK/PSK mode mixer (D32 and D33) with the MLO2(8.224MHz) output, converted to the 2nd IF (24kHz), andamplifi ed by the IF AMP (IC10).These signals are output to the DSP unit (X53-453)through the MRIF connector (CN137).Fig. 7 From the 2nd IF to the MRIF outputCF1 455kHz BPFBW: 9kHz (Narrow)IC12FM AF AMP FM(AF)CF2SSB, CW, AM,FSK, PSKD32,D332rd mixerFM IC9FM ICD31SwitchingIF input(8.248MHz)IC10IF AMPSSB, CW, AM,FSK, PSK(24kHz)455kHz BPFBW: 12kHz (Wide)MRIFCN13724kHzIC11MultiplexerBand Preselector operation frequency1.8MHz 1.7975~2.00499MHz3.5MHz 3.4925~4.01749MHz5MHz 5.2400~5.46999MHz7MHz 6.9800~7.33999MHz10MHz 9.9800~10.17999MHz14MHz 13.9500~14.44999MHz18MHz 18.0180~18.26799MHz21MHz 20.9000~21.69999MHz24.9MHz 24.7900~25.18999MHz28MHz 27.9000~29.89999MHzTable 7 Preselector operation frequency |
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