FP520 Service Manual
Page 10 of 64
Q1
：
5C switch, controlled by MCU.
5C
：
The 5V power source controlled by power saving, and it supplies power for frequency synthesizer unit.
3.8 MCU Unit
MCU unit controls every unit operation of the radio to perform all the radio functions.
Communicates with the external PC
Deposits and withdraws the radio status data
Controls PLL to generates the local oscillation frequency of receiving and transmitting
Acquires the current channel status
Controls the LED status indication
Controls the power supply status of every unit
Detects the operation of every function key
Generates CTCSS signal
Generates DCS signal
Generates power-controlled signal
Completes CTCSS decoding
Completes DCS decoding
Squelch detection and control
Controls the content of voice prompt
Memorizer
（
E
2
PROM
，
AT24LC512BN
）
It stores the radio channel data, CTCSS/DCS data, other function setting data and parameter adjustment data.
CTCSS/DCS Signal Encoding and Decoding:
The CTCSS/DCS signal generated by MCU is sent separately to VCO and TCXO for modulation.
The CTCSS/DCS signal from the receiver is sent to MCU for decoding. The MCU identifies whether the
CTCSS/DCS signal of the radio is the same as the receiving signal so as to turn on the speaker.
CTCSS
CTCSS
（
continuous tone control squelch system
）
，
a squelch control system modulated on the carrier with the
CTCSS signal being the pilot frequency. If the CTCSS feature is set, the conversation is enabled only when the
CTCSS frequency from the receiver and transmitter is the same to avoid interference from other signals.
39 groups of standard CTCSS frequency of this radio are available. See Chart 1.
CTCSS signal is generated by MCU (PWM wave form), and it is sent to VCO for modulation after being filtered by
the low pass filter composed of RC for eliminating the frequency higher than 300Hz.
Chart 3.1 CTCSS Frequency Chart
No.
Frequency [Hz]
No.
Frequency [Hz]
No.
Frequency [Hz]
No.
Frequency [Hz]
1
67.0
11
94.8
21
131.8
31
186.2
2
69.3
12
97.4
22
136.5
32
192.8
3
71.9
13
100.0
23
141.3
33
203.5
4
74.4
14
103.5
24
146.2
34
210.7
Summary of Contents for FP520
Page 1: ... 键入文档副标题 gh 选取日期 在此处键入文档的摘要 摘要通常是对文档内容的简短总结 在此处键入文档的摘要 摘要 通常是对文档内容的简短总结 ...
Page 44: ...FP520 Service Manual Page 43 of 64 Figure 1 FP520 01 Mainboard Schematic Diagram 136 174MHz ...
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Page 54: ...FP520 Service Manual Page 53 of 64 Figure 4 FP520 02 Mainboard Schematic Diagram 400 470MHz ...
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Page 64: ...FP520 Service Manual Page 63 of 64 Figure 7 KBC 51 7 4V Electrical Schematic Diagram ...
