Kenwood TK-2302 Service Manual

Also see for TK-2302: Instruction manual Instruction manual Instruction manual

Contents

TK-2302/2302( V ) /2306114. Transmitter System■ Microphone AmplifierThe signal from the microphone passes through theIC308. When encoding DTMF, it is turned OFF for mutingthe microphone input signal by IC308.The signal passes through the Audio processor (IC308)for the maximum deviation adjustment, and goes to theVCO modulation input.AGCLPFLPFVCOLPF TCXOMICDTMFIC308AQUA-LIC306MCUQTVCOQTTCXOX1Fig. 6 Microphone amplifier■ Drive and Final AmplifierThe signal from the T/R switch (D10 is on) is amplifiedby the pre-drive (Q101) and the drive amplifier (Q102) to800mW.The output of the drive amplifier is amplified by the RFpower amplifier (Q105) to 5.0W (1W when the power islow). The output of the RF power amplifier is then passedthrough the harmonic filter (LPF) and antenna switch (D103)and applied to the antenna terminal.FromT/R SW(D10)DriveAMPPre-driveAMPQ101 Q102RF powerAMPQ105ANTSW LPFD103ANTVDDVGIC101(1/2)IC101(2/2)R117R120R123+BPCTV(IC306)5TVD VGFig. 7 Drive and final amplifier and APC circuit■ APC CircuitThe APC circuit always monitors the current flowingthrough the drive amplifier and RF power amplifier (Q102and Q105) and keeps a constant current.The voltage drop at R117, R120 and R123 is caused bythe current flowing through the RF power amplifier anddrive amplifier, and this voltage is applied to the differentialamplifier IC101 (1/2).IC101 (2/2) compares the output voltage of IC101 (1/2)with the reference voltage from IC306. The output of IC101(2/2) controls the VG of the RF power amplifier and driveamplifi er to make both voltages the same.The change of power high/low is carried out by thechange of the reference voltage.■ Encode Signaling• QT/DQTQT/DQT data of the QTTCXO Line is output from pin 14of the MCU. The signal passes through a low-pass CR filterand goes to the TCXO (X1).The QT/DQT data of the QTVCO Line is output from pin15 of the MCU. The signal passes through a low pass CR fil-ter, mixes with the audio signal, and goes to the VCO modu-lation input. TX deviation is adjusted by the MCU.• DTMFHigh-speed data is output from pin 74 of the MCU. Thesignal passes through a low-pass CR filter, and provides aTX and SP out tone, and is then applied to the audio proces-sor (IC308). The signal is mixed with the audio signal andgoes to the VCO.TX deviation is adjusted by the MCU.• MSK (Fleet Sync)Fleet Sync utilizes 1200bps and 2400bps MSK signal isoutput from pin 6 of IC308. And is routed to the VCO. Whenencoding MSK, the microphone input signal is muted.5. Power SupplyThere are four 5V power supplies in the transceiver: 5M,5C, 5R, and 5T. 5M for MCU is always output while thepower is on. 5M is always output, but turns off when thepower is turned off to prevent malfunction of the MCU.5C is a common 5V and is output when SAVE is not setto OFF.5R is 5V for reception and output during reception.5T is 5V for transmission and output during transmission.6. Control CircuitThe control circuit consists of a MCU (IC306) and itsperipheral circuits. It controls the TX-RX unit. IC306 mainlyperforms the following:1) Switching between transmission and reception by thePTT signal input.2) Reading system, group, frequency, and program datafrom the memory circuit.3) Sending frequency program data to the PLL.4) Controlling squelch on/off by the DC voltage from thesquelch circuit.5) Controlling the audio mute circuit by the decode data in-put.6) Transmitting tone and encode data.CIRCUIT DESCRIPTION