Kenwood TH-77A Service Manual page 18

IH-77A/E
18
Device Functions
2. TX-RX Unit (X57-3630-XX)
Reference No.
Function Description
VCO ripple filter amplifier
PLL buffer amplifier
VHF driver initial stage
VHF driver final stage Output level: 14 to 15 dBm (typical)
IF post-amoplifier
VHF receiver mixer
VHF receiver amplifier
Power switch Air band is on. AMR band is off
Power switch
Power switch
Sub-UHF power
Squelch switch Turned on or off using noise detection output signal.
1
Squeich and hysteresis switches Turned on or off using output signal of Q11.
Q13
Noise amplifier
VCO ripple filter amplifier
PLL buffer amplifier
UHF driver initial stage
Q204
UHF driver final stage Output level: 12 to 13 dBm (typical)
UHF receiver mixer
UHF receiver amplifier second stage
Q207
UHF receiver amplifier initial stage
360/800 daughter power switch
360/800 daughter power switch
2
6
AGC control diode
D10 Receiver filter band shift
Receiver filter band shift
D12
Receiver filter band shift
D13
D16
D1i5 Power switch reverse-current prevention
D201 Ripple filter speed-up
IC2 input pin voltage control (for air band)
Sub-UHF power reverse-current prevention
Squelch/noise detection
VCO output selection switch
Driver final-stage bias
D207
D208
D209
D202
D203
D204 Antenna switch
D205 Antenna switch
D206 Antenna switch
VCO output selection
360/800 power line reverse-current prevention
D210 Mixer input selection switch
UHF power line reverse-current prevention