VHF (136-174MHz) Information
Service Manual
396
11. VHF (136-174MHz) Information
11.1
Transmitter Circuit
The transmitter circuit is mainly composed of:
RF power amplifier circuit
Low-pass filter circuit (for suppressing harmonics)
Auto power control circuit (APC) (including temperature detection circuit)
Sa
mp
ling
re
sist
or
Figure 11-1 Diagram of Transmitter Circuit
11.1.1
RF Power Amplifier Circuit
The carrier signal generated by the TX VCO is modulated and amplified, and then feeds to the
transmitter circuit via the following steps.
Step 1
The signal passes through a
π
-type attenuator first, allowing interstage isolation between the
RF power amplifier circuit and TX VCO.
Step 2
The signal goes to a pre-driver amplifier (2SC3356) for pre-amplification, providing further
interstage isolation.
Step 3
The signal goes to another pre-driver amplifier (2SC4988) and a driver amplifier (RD01) for
further power amplification, to provide appropriate signal to the final-stage amplifier (RD07) for
final power amplification.
Summary of Contents for PD70X Series
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Page 50: ...PD70X PD70XG HD705 HD705G PCB View Channel Board Top Layer 40 ...
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Page 54: ...PD78X PD78XG HD785 HD785G PCB View Keyboard Top Layer 44 ...
Page 55: ...PD78X PD78XG HD785 HD785G PCB View Keyboard Bottom Layer 45 ...
Page 57: ...PD70X PD70XG PD78X PD78XG HD705 HD705G HD785 HD785G Block Diagram Baseband Section 47 ...
Page 127: ...Service Manual UHF1 400 470MHz Information 117 Transmitter Circuit ...
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Page 139: ...PD70X PD70XG HD705 HD705G PCB View Channel Board Top Layer 129 ...
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Page 143: ...PD78X PD78XG HD785 HD785G PCB View Keyboard Top Layer 133 ...
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Page 146: ...PD70X PD70XG PD78X PD78XG HD705 HD705G HD785 HD785G Block Diagram Baseband Section 136 ...
Page 217: ...Service Manual UHF2 450 520MHz Information 207 Transmitter Circuit ...
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Page 229: ...PD70X PD70XG HD705 HD705G PCB View Channel Board Top Layer 219 ...
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Page 233: ...PD78X PD78XG HD785 HD785G PCB View Keyboard Top Layer 223 ...
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Page 236: ...PD70X PD70XG PD78X PD78XG HD705 HD705G HD785 HD785G Block Diagram Baseband Section 226 ...
Page 307: ...Service Manual UHF3 350 400MHz Information 297 Transmitter Circuit ...
Page 318: ...PD70X PD70XG PD78X PD78XG HD705 HD705G HD785 HD785G PCB View Main Board Bottom Layer 308 ...
Page 319: ...PD70X PD70XG HD705 HD705G PCB View Channel Board Top Layer 309 ...
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Page 323: ...PD78X PD78XG HD785 HD785G PCB View Keyboard Top Layer 313 ...
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Page 326: ...PD70X PD70XG PD78X PD78XG HD705 HD705G HD785 HD785G Block Diagram Baseband Section 316 ...
Page 401: ...Service Manual UHF5 806 941MHz Information 391 Transmitter Circuit ...
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Page 418: ...PD78X PD78XG HD785 HD785G PCB View Keyboard Top Layer 408 ...
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Page 421: ...PD70X PD70XG PD78X PD78XG HD705 HD705G HD785 HD785G Block Diagram Baseband Section 411 ...
Page 494: ...VHF 136 174MHz Information Service Manual 484 Transmitter Circuit ...