Kenwood TK-5210 Service Manual

Also see for TK-5210: Specifications Instruction manual Specifications Instruction manual Instruction manual

Contents

TK-521015CIRCUIT DESCRIPTION(Q407) adjusts the signal path so that the audio signal is inputto the CODEC through the scrambler board.The audio signal is input to the CODEC (base band circuit)through the above path.4-2. Base Band CircuitThe base band circuit of the transmitter system consistsof the following:• CODEC (IC406)• DSP (IC411)• LPF (IC407)• Buffer (IC409)• DAC (IC411)• Amplifier (IC412)The audio signal output from the base band circuit isconverted to digital data of a sampling frequency of 48 kHzand a quantization resolution of 16 bits by the CODEC(IC406). This digital data is sent to the DSP (IC8), and voicesignals of 300 Hz or lower and frequencies of 3 kHz or higherare cut off and an audio range 300 Hz to 3 kHz is extracted.The audio signal is then pre-emphasized in FM mode andsynthesized with the signals, such as QT and DQT, asrequired, and is then output from the CODEC. In APCOmode, the audio signal is converted to the C4FM base bandsignal and output from the CODEC. The DTMF and MSK baseband signals are also generated by the DSP and output by theCODEC.LPF (IC407) removes quantization noise from the baseband signal output from the CODEC.The buffer (IC409) sets the base band signal level to theDAC input range.The DAC (IC411) assigns the base band signal to the VCO(Q311) and VCXO (X301).At this time, the level output according to the transmitcarrier is fine-adjusted according to the modulation methodof FM Wide, FM Narrow and APCO.4-3. Transmit Signal Amplification Circuit(From T/R switch to Final amplifier)The transmit signal passing through the T/R switch(D101) is amplified to approx. 50 mW by the two transistoramplification circuits (Q101, Q102). The transmit signaloutput from Q102 passes through a 3dB attenuator toimprove high-frequency signal matching is amplified by thedrive amplifier (Q103) and applied to the final amplifier(Q105). The signal applied to the final amplifier is amplified bythe final amplifier so that the antenna output is 5 W (1 W forLow Power).4-4. High-Frequency Signal Switch Circuit(From Antenna switch to ANT output)The transmit signal output from the final amplifier (Q105)passes through the antenna switch (D106, D107) and LPF,and goes into the SPDT switch (IC102, IC103) which changesthe antenna connector (CN101) and the universal connector(CN102).The transmit signal passing through the output changeswitch passes through the surge protection HPF andspurious removing LPF and then goes to the antennaconnector (CN101) or the universal connector (CN102),specified by the SPDT switch (IC102, IC103).4-5. APC CircuitThe APC circuit detects the current of the drive amplifier(Q103) and final amplifier (Q105) during transmission andcontrols the output power by controlling the current.It detects the current using R119 and R120 and applies adrop voltage between both resistors during transmission toAPC (IC101). It controls the transmission current of the driveamplifier and final amplifier so that it is constant bycomparing this current with the reference voltage outputfrom pin 7 of IC104. The reference voltage input to pin 5 ofIC104 is output from the DAC (IC411). High/Low poweroutput is set according to the DAC output voltage.4-6. Temperature Protection CircuitThe temperature protection circuit reduces the APCvoltage when the temperature of Q105 rises, to preventthermal destruction of the final amplifier (Q105). The CPUFig. 6 Audio band and Base band circuitFig. 7 Transmitter circuitMIC(MAIN)EXT.MICMIC(SUB)MSW/CTSMMIC603 Q410SWQ406SW AGC-AMPIC405LPFD402,D403DETScrambler boardSCSWMICN/CAMPIC411DACQ407SWIC8DSPIC406CODECIC407LPFIC409BUFFIC412AMPX301VCXOQ311VCOD101T/R SWQ103Drive AmpQ105Final Amp D106,D107ANT SWIC101APCR119+BR120APC SWQ101Pre PreDrive AmpQ102PreDrive Amp 3dBAttenuatorIC102,IC103SPDTCN101CN102LPF(IC5) detects the temperature with a thermistor (TH101) tocontrol the reference voltage to the APC circuit.