Connect Systems CS700, Service Manual

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DR6000-2/DR7000-2 Service Manual
22
Chapter 5 Circuit Description
5.1 Frequency configuration
The reference frequency of frequency synthesizer is provided by 16.8MHz crystal oscillator X1 TCXO.
The receiver adopts quadric mixing mode. The first IF is 49.95MHz, and the second IF is 450kHz. The
first local oscillation signal of the receiver is produced by frequency synthesizer and the second local
oscillation signal selects the 4
rd
harmonics of 16.8MHz of crystal oscillator X1 TCXO. The signal of
transmitter is produced by frequency synthesizer directly.
Figure 1 Frequency configuration
5.2 Receiver
（
Rx
）
The receiver is double conversion superheterodyne,designed to operate in the frequency range of
400 to 470MHz,The frequency configuration in Fig 1.1
Figure 2 Receiver section configuration
Front End of Receiver
Signals from the antenna are filtered by BPF which consists of C235 C236 C233 C604 C252 C951 C234