make 25KHz-reference frequency.
Transmit frequency is generated on the Inductor and Capacitor circuit with connected to
IC2 pin 4,5.
The frequency control voltage, which is output from IC2 pin 7, will be input into Variable
Capacitance Diode(D6) on Inductor and Capacitor circuit.
The receiver local frequency is generated on the Inductor and Capacitance circuit with
connected to IC2 pin 20, 21.
The frequency control voltage, which is output from IC2 pin 18, will be input into Variable
Capacitance Diode(D5) composed on
The oscillating frequency 21.25MHz which is output from IC2 pin 11 will be used for the
second local frequency of Receiver and it will be input into IF IC(IC2) pin 1.
10.4 Transmitting Circuit Operation
3.4.1 Microphone Amplifier Circuit:
Voice signal from the mocrophone goes through pre-emphasis circuit consisting of
C147 ,R104 and is amplified in MIC AMP IC8(A).
Pre-emphasis can be output by Diode(D10). The level of the signal is limited by D7
and adjusted in the VR4.
Limiter output is amplified by IC8(B),then it goes through the active 4-stage LPF
consisting of IC8(C) and IC8(D). 4-stage LPF output goes into Variable Capacitance
Diode(D7) and then it makes Frequency modulation.
3.4.2 Transmit Frequency Power Amplifier Circuit
RF signal from the PLL IC(IC2) pin 1 goes through the 10dB attenuator consisting of
R37,R38,R39 and will be amplified by Q11. Output from Q11 will amplify drive power
necessary for the Q4 and Q3. power module(IC5) will be amplified and the RF signal
will be output to the antenna switching circuit. 4-stage LPF consisting of L21 and
L1-L3 is used to improve the level of Transmission Spurious Emission. RF output
from the power module(IC5) can be changed by changing the voltage of IC5 pin2.
