Service Manual
UHF1 (400-470MHz) Information
37
7.3.2
Working Principle of VCO
VCO employs Colpitts oscillator circuit (the RX oscillator circuit is composed of D102, D103, D106, D107
and L112; the TX oscillator circuit is composed of D108, D109, D110, D101 and L117). It obtains
different output frequencies by changing the varactor's control voltage (i.e. CV voltage).
There are two types of VCO: TX VCO and RX VCO. Both types control EMD22 to switch operating
status via OMAP. RX VCO is composed of the oscillator loop and Q104, to provide LO signal. TX VCO is
composed of the oscillator loop and Q108, to provide carrier for TX signal.
7.3.3
Two-point Modulation
In TX mode, the two-point modulation technology is employed, to obtain higher modulation accuracy and
lower 4FSK bit error rate. MOD-VCO and MOD-XO send the modulation signal to the modulation end of
VCO and the reference crystal oscillator of PLL respectively to modulate TX VCO and the reference
crystal oscillator.
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 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 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 ...