Frequency Generation Unit (Fgu); Pll Synthesizer; Reference Oscillator; Pll Ic - Hytera MD78X Service Manual

VHF (136-174MHz 50W) Information
the LC resonance loop (D702, L715 and C745).
DSP (U302) gets the audio signal from IF IC (U701). Then this signal goes through U302 to output
data signal, which is sent to U231 and PIN44 (SSI_DI) for digital-to-analog conversion. Finally, the
output analog audio signal will be subjected to gain control, and then fed to the speaker.
15.3

Frequency Generation Unit (FGU)

15.3.1

PLL Synthesizer

The PLL synthesizer that consists of the reference oscillator (X100), PLL IC (U100) and VCO, is
utilized to supply excitation signal source to the transmitter, and local oscillator signal to the receiver.
15.3.2

Reference Oscillator

X100 is a 19.2MHz TCXO, and its reference frequency is calibrated by the digital-to-analog converter
(U500) for accuracy.
15.3.3

PLL IC

The PLL IC (U100) is a fractional frequency divider. The logic IC U101 and U102 work with the PLL IC
(U100) to achieve locking.
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Service Manual