Figure 2-9:Uhf Vco Block Diagram - Motorola Professional Radio Service Manual

transmit mode, the audio signal to be frequency modulated onto the carrier is received through U201
(pin 41).
When a high impedance is applied to U241 (pin 19), the VCO operates in BATTERY SAVER mode. In
this mode, both the receive and transmit oscillators as well as the receive transmit and prescaler
buffer are turned off.
Rx-SW
Tx-SW
(U201 Pin 28)
Steer Line
Voltage
(VCTRL)
RX RX VCO
Tank Circuit
TX TX VCO
Tank Circuit
Desired Mode
Tx
Rx
Battery Saver
Pin 20
Pin 7
TX/RX/BS
Pin 13
Switching Network
Pin 3 Vcc-Superfilter
Collector/RF in
Pin 4
Pin 5 RX
Rx Active
Pin 6
Pin 16 TX
Tx Active
Pin 15
Vsens
Circuit
Pin 18
Vcc-Logic
(U201 Pin 28)
Figure 2-9: UHF VCO Block Diagram
Table 2-5 Level Shifter Logic
AUX 4
Low
High
Low
Level Shifter
Network
TRB_IN
Pin 19
Presc
U241
VCOBIC
RX
Bias
TX
Bias
Pin 2 Pin 1 Pins 9,11,17
Rx-I adjust
Tx-I adjust
AUX 3
High (@3.2V)
Low
Low Hi-Z/Float (@2.5V)
5V
AUX3 (U201 Pin 2)
AUX4 (U201 Pin 3)
Prescaler Out
Pin 12
U201 Pin 32
LO RF INJECTION
Pin 8
Matching Low Pass
Network
Pin 14
(U201 Pin 28)
VCC Buffers
Pin 10
TX RF Injection
Attenuator
TRB
High (@4.8V)
Low
2-11
Filter