Kenwood TS-990S Service Manual

Also see for SP-990: Instruction manual

Contents

TS-990S20CIRCUIT DESCRIPTIONBand BPF selection classifi cation IF switching frequency criteriaIF frequencyTX IF Sub RX IF135kHz f  522kHz f  522kHz73M73M SRX-2BC 0.522  f  1.705MHz 0.522  f  1.705MHz 73M SRX-21.8MHz 1.705  f  2.5MHz1.705  f  2.1MHz 11M SRX-12.1  f  3.4MHz 73M SRX-23.5MHz 2.5  f  4.1MHz3.4  f  4.1MHz 11M SRX-15MHz 4.1  f  6.9MHz 4.1  f  6.9MHz 73M SRX-27MHz 6.9  f  7.5MHz 6.9  f  7.5MHz 11M SRX-110MHz7.5  f  10.5MHz 7.5  f  10.5MHz 73M SRX-210.5  f  13.9MHz 10.5  f  13.9MHz 73M SRX-214MHz 13.9  f  14.5MHz 13.9  f  14.5MHz 11M SRX-118MHz14.5  f  21.5MHz14.5  f  20.9MHz 73M SRX-221MHz 20.9  f  21.5MHz 11M SRX-128MHz 21.5  f  30.0MHz 21.5  f  30.0MHz 73M SRX-250MHz (TX) 49.0  f  54.0MHz 49.0  f  54.0MHz - -50MHz (RX) 30.0  f  60.0MHz 30.0  f  60.0MHz - 73M SRX-2Table 13 Criteria for selecting the SRX-1 path or SRX-2 path4-3. 2nd IF Frequency (10.695MHz/11.374MHz)The 2nd IF signal passing through the SRX-1 or SRX-2path is amplified by approximately 16 dB in the 2nd IF am-plifier 1 (Q481), and is then distributed into 2 paths, the NBcircuit and the blanking circuit (D481 to D484). Blanking isimplemented by D481 to D484 for the signal from the NB cir-cuit. The 2nd IF signal then passes through the IF filter. Oneof 5 filters is selected, depending on the frequency and themode. (Refer to Table 14.)The 2nd IF signal passing through the IF filter is input tothe AGC amplifier (Q491). AGC voltage output from the DSPis input to the gate2 terminal of Q491, and the gain of AGCamplifier is controlled. Next, the signal is amplified to ap-proximately 20 dB by the 2nd IF amplifier (Q494 and Q495)and passes through the ATT diode (D501). The voltagedetermined in the adjustment mode is applied to D501, andthe difference of the total gains between SRX-1 and SRX-2paths have adjusted.IFfrequency IF filterModeFM AM SSB FSK CW10.695MHz15kHz6kHz2.7kHz11.374MHz2.7kHz500HzTable 14 Selecting the IF filterFig. 18 2nd IF frequency (10.695MHz/11.374MHz)Q481Sub 2nd IF AMP 1IF input(11.374MHz)IF input(10.695MHz)D481~484Noise blanking D487D495XF48110.695M 15kXF48210.695M 6kD490TXD496XF48410.695M 2.7kD488D503 XF485D491D505TXD494D504D492D50611.374M 2.7kD489 XF48611.374M 500D493Q491Sub AGC AMPSAGCVQ494,495Sub 2nd IF AMP 2D501ATTSIFGCIF output(10.695MHz/11.374MHz)