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2) Transmitter System
1. Modulation Circuit
The microphone amplifier IC1 (IDC, LPF) consists of two operational amplifiers. The signal from the microphone is led to pre-emphasis circuit consisting of C36 and R47 and then to the limiter circuit. The limiter circuit uses the saturation of the OP amplifier. The amplified signal is input to the low-pass filter IC1A. The output signal from the microphone amplifier is passed through variable resistors VR2 for modulatlon adjustment and input to the VCO unit. Sub tone deviation is determined by R24, R25 and VR2. The radio does not have the adjustment variable resistor for sub tone deviation. 2. TX Amp. Circuit The signal from VCO is ampriied by TX, RX wide band LO amplifier Q19. The signal from Q19 is passed through the transmission/reception selector, and amplified byQ20 and Q15. The PA unit is driven at 200mW driving power. 3. PA Circuit IC5 is 20W(M06DX) powered amplifier module. The output power is controlled by the voltage of V1. The RF signal amplified 20W in PA is passed through D3 and three-stage transmission/reception low-pass filter, and input to the antenna connector. 4. ALC Circuit (M06DX) The power detection circuit consisting of D17 and D18 rectifies the output signal voltage. The detected DC voltage is led to the VR1 (power adjust trimmer), and amplified by Q3, Q9 and Q13. Output power is controlled by voltage of V1 in IC5 and collector voltage of Q15. When the temperature goes up unusually, the power down circuit consisting of R101 and TH2 works to prevent the device from the destruction. (M06DX) The VCO unit is designed for the PLL circuit, putting the VCO on one side, and PLL circuit on the other side. Q301 in the VCO is grounded using the gate oscmator, and its frequency covers 50MHz to 54MHz without transmission/reception shift circuit. IC301 is pulse swallow system based PLL IC with the built-in prescaler, which synthesizes 150MHz-band signal. The loop filter consisting of Q302 and Q303 is the active type.
3)PLL Circuit
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