TC-265/365 SERVICE MANUAL
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17
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2) CTCSS/CDCSS encoder
A necessary signal for CTCSS/CDCSS encoding is generated by MCU and FM-modulated to the PLL
IC reference signal. Since the reference OSC does not modulate the loop characteristic frequency or
higher, modulation is performed at the VCO side by adjusting the balance. (See Fig. 6)
3) 2-Tone/5-Tone encoder
The necessary signal for 2-Tone/5-Tone encoding is generated by MCU. The signal is sent to
IC500(TC-265
)
/IC1
(
TC-365
)
(2/2), and then applied to 3KHz low-pass filter. The resulting signal is
applied to VCO for direct modulation (See fig. 6).
MCU
MUTE
PRE EMPHASIS
LPF
IDC
MAX DEV
VCO
(TCXO)
OSC
REFERENCE
MIC
MIC AMP
TO
2 TN/5 TN
Decoder
Balance
MUTE SW
Fig. 6. Transmit audio CTCSS/CDCSS
4-a) RF amplifier (TC-265)
The RF signal obtained from the VCO buffer amplifier Q100 is amplified by Q101 and Q102. This
amplified signal is passed to the power amplifier, Q102 and Q105, which consists of a 2-stage FET
amplifier and is capable of producing up to 4.5W of RF power (See Fig. 7-a).
1
2
3
4
A
B
C
D
4
3
2
1
D
C
B
A
Title
Number
Revision
Size
B
Date:
22-Nov-2003
Sheet of
File:
D:\TC366 CE\service manual\service\
周工
031120\
维修手 册插图
.DDB
Drawn By:
5T
AMP
DRIVE AMP
FINAL AMP
SW
ANT SW
LPF
ANT
B SW
APC
SW
B
APC
5T
5T
SW
Fig. 7-a. APC system
4-b) RF amplifier (TC-365)
The RF signal obtained from the VCO buffer amplifier Q136 is amplified by Q135 and Q134. This
amplified signal is passed to the power amplifier, Q131 and Q129, which consists of a 2-stage FET
amplifier and is capable of producing up to 4W of RF power (See Fig. 7-b)