Kenwood R-2000 Service Manual

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R-2000CIRCUIT DESCRIPTIONItem RatingCenter frequency 455 kHz ± 0.6 kHz6 dB band width 2.s ±0.3 kHz40 dB band width 5.5 kHz or lessInsertion loss (at maximum output) 6.0 dB or lessGuaranteed attenuation 55 dB or more(within 455 ± 100 kHz) ,Spurious attenuation(within 0.1 to 1.0 MHz) 45 dB or morefor 600 to 700 kHz. 40 dB or more1/0 matching impedance 2.0 k.QTable 2. Ceramic filter {L72-0332-05, RX unit F3)SSS, AM-N, CW-WItem RatingNominal center frequency 455 kHz6 dB band width ± 3 kHz or more(from 455 kHz)50 dB band width ± 9 kHz or less (from 455 kHz)Ripple (within 455 ± 2 kHz) 2 dB or lessInsertion loss 6 dB or lessGuaranteed attenuation 60 dB or more(within 455 ± 100 kHz)1/0 matching impedance 2.0 k.QTable 3. Ceramic filter (L72-0319-05, RX unit F4)AM-WItem RatingNominal center frequency 455 kHz6 dB bandwidth ± 7.5 kHz or more50 dB bandwidth ± 15 kHz or lessRipple (within 455 ± 5 kHz) 3 dB or lessLoss 6 dB or lessGuaranteed attenuation 35 dB or more(within 455 ± 100 kHz)Input and output impedance 1.5 k.QTable 4. Ceramic filter (L72-0316-05, RX unit F5)FMItem RatingCenter frequency fo 455.7 kHzCenter frequency deviation fo ±50 Hz at 6 dB6 dB bandwidth ±250 Hz or more60 dB bandwidth ±425 Hz or lessRipple 2 dB or lessLoss 6 dB or less80dB or moreGuaranteed attenuation at 100 Hz to 455. 1 kHz and456.3 kHz to 2 MHzlmput and output impedance 2kQ#'15 pFTable 5. CW Crystal filter (L71-0206-05)YG-455C (Option)4Item RatingCenter frequency quency f o 455.7 kHzCenter frequency deviation Jo ±50Hzat6dB6 dB bandwidth ± 1 25 Hz or more60 dB bandwidth ± 250 Hz or lessRipple 2 dB or lessLoss 6 dB or less80 dB or more atGuaranteed attenuation 100 Hz to 455.3 kHz and456.1 kHz to 2 MHzInput and output impedance 2 k.Q // 15 pFTable 6. CW Crystal filter (l71-0207-05)YG-455CN (Option)PLL (Phase locked loop) unit XS0-1920-00The PLL unit houses the PU. oscillator circuit, microproces-sor control circuit and the NB amplifier circuits. In the PLLcircuit, there is a 9 MHz reference frequency crystal oscilla-tor, the first local oscillator (45.90 ,..., 75.85 MHz), secondlocal oscillator (36 MHz) and third local oscillator (9.395 ,...,9.445 MHz), which are output to the Receiver unit.The digital circuit peripheral to the microprocessor controlsthe PLL circuit frequency, display, clock/timer, input inter-face, rotary encoder mode (speed) and memory.1. PLL circuit1) Reference frequency oscillator01 operates at a reference frequency of 9 MHz, whichis supplied to the second and third local oscillator cir-cuits through buffer 02.Via buffer 03, a 4.5 MHz signal divided 1/2 by IC 1 issupplied through buffer 04 to the first local oscillatorPLL circuit. The reference frequency is also buffered(06) and divided down to 1 kHz by IC2 for use as aclock reference signal.2) First local oscillator circuit (LO 1)The first local oscillator is obtained from the PLL(Phase Locked Loop) circuit. Three VCOs (VoltageControlled Oscillator) controlled by the microproces-sor through 020 ,.., 22 cover the 45.90 ,..., 75.85MHz frequency range. The VCO output is amplified by026. 027 and 028. Part of the signal is applied tobuffer 016:. 2SC1907 and PLL IC5: MN614 7C. Thespurious component is eliminated from the remainingsignal by a BPF and is output via. buffer 029 and030: 2SC 1707 as the LO 1 signal.IC5: MN6147C consists of a programmable fre-quency divider. reference frequency divider and phasecomparator which compares the reference and VCOfrequencies (comparision frequency; 25 kHz). Theprogrammable divider's ratio ( 1836 ,.., 3034; onlyeven number) is controlled by the microprocessor.The phase error signal from the comparator is appliedto the VCO by active filter 017, 018 and 019:2SC1775.3) Second local oscillator (L02)The reference frequency is quadrupled by 05:2SC 1815 to obtain the 36 MHz second local oscilla-tion frequency.