Power Amplifier Circuit - Icom IC-4A Instruction Manual

the bias voltage of O11 ~ 014.
This prevents transmission of unwanted signals.
POWER AMPLIFIER CIRCUIT
The output signals from Q13 is fed to the power amplifier Q14, and amplified to 1.5 watts.
In the transmit mode, D16 and D17 are turned ON, and D17 makes L31 has high-impedance and
D16 feeds the signals to the antenna through the low-pass filter.
PLL CIRCUITS
LOCAL OSCILLATOR CIRCUIT
The crystal oscillator Q7 oscillates 45.35556MHz with X2 for receive, 47.77778МН2 with X4 for
simplex transmit, 47.22222MHz with ХЗ for —5MHz and 48.33333MHz with X5 for +5MHz duplex
transmit, and the signal at three times this frequency is taken from the collector of Q7, and fed to the
mixer of the PLL circuit.
In the receive mode, R+5V is applied to D8 through R23, L9, 113 and R27 and О8 is turned ON and
selects X2.
In the simplex transmit mode, Т+БМ is applied to 010 through R25, L11, L15 and R29 апа Γ10 is
turned ON and selects X4.
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