QUANTUN QP-750 Service Manual
Also see for QP-750: User manual
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Contents
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QP-750 Service Manual- 36 -7.5.1 CTC/CDCTransmit：CTC/CDC signaling produced by CTC_PLL pass a low pass filter and then entersVCXO.CTC /CDC signaling produced by CTC_OUT pass a low pass filter and thenmixed with AF before enters VCO.Receive: Demodulated signal enters MCU after pass IC1404、IC1405. MCU then judges whetherCTC/CDC matches the preset values or not. According the result, the out tone will becontrolled by AFMUTE.7.5.2 DTMF / 2-ToneTransmit: The signal produced by MCU provides a TX and SP out tone, and is then applied to thebase band processing IC. The signal in mixed with the audio signal and goes to theVCO.Receive: Demodulated signal is filtered after passing base band processing IC, and then entersMCU for decoding.7.5.3 MSKTransmit: MSK signal produced by base band processing IC enters VCO together with AF signalfor modulation.Receive: MSK input of demodulating IC is sent to AK2346 for demodulation after being amplified.The demodulated signal is then sent to MCU for decoding.7.5.4 AFTransmit: AF signal from MIC enters base band processed IC for amplification, pre-emphasis etc.after being amplified. And then it enters VCO for modulation.Receive: Demodulated AF signal enters the base band processing IC for amplification,de-emphasis etc. after being amplified. And then it enters AF power amplifier drivedspeaker. Base band processed chip provides functions for processing signal asamplifying, filtering, emphasizing, scrambling, companding, and amplitude limiting. |
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