Circuit Description - HYT TC-610P Service Manual

Circuit Description

1. PLL Frequency Synthesizer
The PLL circuit mainly provides the local oscillator signal for Rx and RF carrier signal for Tx. It
is composed of VCO and baseband processor, allowing frequency tracking and channel
switching under the control of MCU signals.
1 ） PLL
U605
MB95F108AK
WPFV-GE1
The step frequency of the PLL circuit is 5.0KHz, 6.25KHz, 10.0KHz or 12.5KHz (selectable). Therefore,
the 38.4MHz reference oscillator signal is divided into 5.0KHz, 6.25 KHz, 10.0 KHz or 12.5 KHz
reference frequencies via a fixed counter in the PLL (at U202). Meantime, the signal from the VCO goes
through the buffer (Q102) and amplifier (Q103), and then it goes to the PLL (at U202), where it is divided
by a variable frequency divider. In the phase detector (PD) of PLL, the new signal derived from
frequency division is compared with the reference frequencies. After passing through a low-pass filter,
the signal from the phase comparator goes to the varactors (D100, D101, D102 and D103) of VCO so as
to control its output frequency.
2） VCO
The VCO section is realized by the oscillator circuit of three-point capacitance.
Q5
1
1
BUFFER
APC/TUNE
L101
L102
LPF
32/33
17bitDIV
Figure 1
11
TC-610P Service Manual
Q6
D100
D104
TX-VCO
D101
D102
Q101
2SK508NV
RX-VCO
D103
12.8MHZ
1/2 CP OSC
EN
DATA
U202
1/2
CLK
21bitDIV
Q100
2SK508NV
T/R-SW