Kenwood TKR-840 Service Manual

Also see for TKR-840: Brochure & specs Instruction manual

TKR-84026CIRCUIT DESCRIPTION2.4 Transmitter main PLL circuitThe transmitter main PLL circuit produces the transmitterfrequency signal and consists of VCO (Q1 and Q2) and asingle-chip PLL IC (IC101). Transmit frequencies of 450.000MHz to 464.995 MHz (K1), 480.000 to 496.995 MHz (K2), and400.000 to 414.995 MHz (K3), are derived from VCO Q1.Transmit frequencies of 465.000 MHz to 480.000 MHz (K1),497.000 to 512.000 MHz (K2), and 415.000 to 430.000 MHz(K3), are derived from VCO Q2.IC101 divides the VCO oscillator signal and the transmitter..'11)4C6""Da. 4I FREQ. CONTROL!,rl••05, 6 iii!MODULATION! RSC23s1I vco oscler Cl4N!: ..; ''I I DC SWITCH I0 .. .,�l .. ·10.. ,PLL reference signal (4.5 MHz) and its phase is comparedwith the 100kHz comparison frequency. The phase differencesignal is converted to a DC signal with a lag-lead type loopfilter. The DC signal is applied to varicap D1, D3, D2, D4 tolock the VCO oscillator frequency with the desired oscillatorfrequency. At the same time, the DC signal passes throughthe IC109 operational amplifier and buffer amplifier, and isoutput as a voltage signal (CVT) for monitoring the transmittermain PLL lock voltage.C27 R19R20.. ....; "Q5R210ROO----+-Qo•••.,"uD1. 3I FREQ. CONTROL I ·1 ... : lC4(Q1) ••D3 C5 LS: C22�· c2e R21Q3. 5L245 L244 Cl U jRF AMPI"u.�1 I DC SWITCH IIC105 CN3CCVT)R1O5 Rl 14 R124ulvco oscjPHI •••PHP vccVDDA RPI-RN RFJ+RP VSSLOCK STBTEST DATVDD CLKIClOl§]"NQ242---+---- IC!5C8PI.N)..ii••---+----1c201CDATA). IC202CSDAT}, IC5(4PIN)1-----+--- IC201 (CLOCK), IC202CSCLK). IC6C10PIN)..'---------- ..Ql 7, 1 C20O. Q2O3Fig.4 Transmitter main PLL circuit2.5 Driver circuitThe driver circuit amplifies the transmitter frequency signalto the level required for input to the final unit (X56-305 8/3).This circuit consists of RF amplifier Q9, RF switch D7, RFamplifier Q13, RF amplifier Q14, and switches 0203, QB, Q10,Q12, and Q11.The transmitter signal level input to Q13 is about 0 dBm (1milliwatt). Since it is amplified by about 15 dB by Q13, andalso amplified by about 8 dB by Q14, the output from Q14becomes about 200 milliwatts. After being attenuated byattenuators R257, R258, and R259, the net output is +20 dBm(100 milliwatts) at drive output connector CN1.