Vco; Figure 13-5 Diagram Of Vco - Hytera MD78X Service Manual

Service Manual UHF3 (350-400MHz 45W) Information
13.3.4

VCO

The VCO is composed of transistors (Q100, Q103, Q106 and Q110), varactors and four Colpitts
oscillators. There are four VCOs in all: two VCOs (Q100 and Q103) used to transmit excitation signals
and the other two VCOs (Q106 and Q110) to receive LO signals. U302 controls the operating
frequency of the VCO. Q102 and Q107 constitute the buffer amplifiers for the transmitter circuit, while
Q111 and Q109 for the receiver circuit. The digital-to-analog converter (U500) modulates the TX
oscillator signal.

Figure 13-5 Diagram of VCO

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