Paragraph Page - Motorola GM1200E Service Manual

Table of Contents
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5.0 Transmit Signalling Circuits ................................................................... 12
5.1 Sub-audible Data (PL/DPL) ....................................................................... 12
5.2 High Speed Data ....................................................................................... 13
5.3 Dual Tone Multiple Frequency (DTMF) Data............................................. 13
6.0 Receive Audio Circuits ............................................................................ 14
6.1 Squelch Detect .......................................................................................... 14
6.2 Audio Processing and Digital Volume Control ........................................... 15
6.3 Audio Amplification Speaker (+) Speaker (-) ............................................. 15
6.4 Handset Audio ........................................................................................... 16
6.5 Filtered Audio ............................................................................................ 16
6.6 RX Secure Audio (optional) ....................................................................... 16
7.0 Receive Signalling Circuits ..................................................................... 17
7.1 Sub-audible Data (PL/DPL) and High Speed Data Decoder ..................... 17
7.2 Alert Tone Circuits ..................................................................................... 17
UHF (403-470MHz) SPECIFIC CIRCUIT DESCRIPTION
8.0 Receiver Front-End .................................................................................. 18
8.1 Front-End Band-Pass Filter & Pre-Amplifier .............................................. 18
8.2 Mixer and Intermediate Frequency (IF) Section ........................................ 19
8.3 IF IC (U5201) ............................................................................................. 19
9.0 Transmitter Power Amplifier (PA) 5-25W ............................................... 19
9.1 Power Controlled Stage............................................................................. 19
9.2 PA Stages.................................................................................................. 20
9.3 Directional Coupler .................................................................................... 20
9.4 Antenna Switch.......................................................................................... 21
9.5 Harmonic Filter .......................................................................................... 21
9.6 Power Control ............................................................................................ 21
10.0 Frequency Synthesis ............................................................................... 23
10.1 Reference Oscillator .................................................................................. 23
10.2 Fractional-N Synthesizer (U5701) ............................................................. 23
10.3 Voltage Controlled Oscillator (VCO) .......................................................... 24
10.4 Synthesizer Operation ............................................................................... 24
3.1-ii
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Introduction/Theory of Operation