Kenwood TS-990S Service Manual

Also see for SP-990: Instruction manual

Contents

TS-990S18CIRCUIT DESCRIPTION4. Sub Receiver CircuitThe configuration of the sub receiver circuit is almost thesame as that of the receiver circuit of the TS-590. In 21MHzor lower major amateur bands and modes that require theTable 11 Mode, conversion method, and IF frequencyMode SSB CW FSK AM FMSRX-1 pathConversion method Double -IF frequency1st 11.374MHz -2nd 24kHz -SRX-2 pathConversion method TripleIF frequency1st 73.095MHz2nd 10.695MHz3rd 24kHz 455kHzresistance to the interference due to nearby strong signals,the signal received passes through the double conversionSRX-1 path. In other frequency bands or modes, the signalpasses through the triple conversion SRX-2 path.4-1. From the Antenna Terminal to the Sub Pream-plifier (Q219)The sub received signal from the antenna terminal pass-es through ANT1 to ANT4 antenna change over relays (K801to K808) in the antenna connector unit (X45-388 B/2), theAT IN/THROUGH changeover relay (K18 and K19) in the an-tenna switch unit (X53-441 B/2), the RX IN/OUT changeoverrelay (K10 to K13), the distributor changeover relay (K14 andK15), the distributor, and image filter, and is applied fromCN18 to CN200 (SRAT) on the TX-RX unit (X57-827 A/2)through a coaxial cable. (Fig. 28)The signal input into the TX-RX unit is applied to the 6 dBand 12 dB attenuators. Each attenuator can be turned ONand OFF individually so that an attenuation level of OFF, 6,12 or 18 dB can be selected. The signal then passes throughthe LPF for IF trap use, surge absorption limiter, and BCband attenuator (except 30kHz to 1.705MHz), and is appliedto the BPF.An 11.7MHz and 15.5MHz trap circuit is embedded inthe BC band attenuator in order to prevent interference fromhigh-power broadcast stations if the model is for Europeancountries.The BPF divides in the range as shown in table 12. Inorder to prevent intermodulation ranging from 522kHz to1.705MHz due to high-power broadcast stations, there is anATT (attenuator).ATT ON: CN210=open, CN220=shortATT OFF: CN210=short, CN220=openThe transmission signal also passes through the BPF.The signal which is passed through the BPF is applied tothe next stage preamplifier (Q219). The sub receiver blockuses an emitter grounding circuit using a bipolar transistorand has a gain adjustment function by the band that usesQ220 to switch the emitter feedback level.The sub preamplifier gain in 30kHz to 21.5MHz is ap-proximately 12 dB and 21.5MHz to 60MHz is approximately20 dB. By turning OFF the P.AMP display with the [P.AMP]key, the preamplifi er (Q219) output is bypassed.Fig. 16 From the antenna terminal to the sub preamplifier (Q219)ATT-6dBLPF522k~1.705MHz1.705M~60Mx11SRAT(Sub RX RF in)ATT-12dBS6DB S12DBLPF~60MHzBC Trap(EU Trap) BPFBPFATTLPF30k~522kHzPRE OFFQ219Sub PRE AMPTo 1st Mixer