Codan 8525B Series Technical & Service Manual page 4

ii Table of Contents
4 Technical Description
4.1 Control and Supply Voltages..............................................................................4-1
4.1.1 Supply Voltages ..............................................................................4-1
4.1.2 Power and Control Lines.................................................................4-2
4.1.3 Overvoltage and Reverse Voltage Protection..................................4-2
4.1.4 Transceiver Power On/Off ..............................................................4-2
4.1 5 High Power Transceiver Protection and Power On/Off ..................4-3
4.2 Receiver..............................................................................................................4-4
4.2.1 Input Filters .....................................................................................4-4
4.2.2 Mixers, First IF Amplifiers and Filters ...........................................4-4
4.2.3 Noise Blanker ..................................................................................4-5
4.2.4 IF Crystal Filter and Amplifier........................................................4-5
4.2.5 Demodulator....................................................................................4-5
4.2.6 Audio Mute .....................................................................................4-6
4.2.7 Volume Control and Audio Amplifier ............................................4-6
4.3 Transmitter Exciter.............................................................................................4-7
4.3.1 Microphone Amplifier.....................................................................4-7
4.3.2 Modulator ........................................................................................4-7
4.3.3 Crystal Filter....................................................................................4-8
4.3.4 Mixers, IF Filters and IF Amplifier.................................................4-8
4.4 Local Oscillators.................................................................................................4-9
4.4.1 Voltage Controlled Oscillators (VCO)............................................4-9
4.4.2 Phase/Frequency Detectors and Dividers ........................................4-9
4.4.3 Lock Signals ..................................................................................4-10
4.4.4 Loading of Frequency Data to Synthesizers ..................................4-10
4.4.5 1650/1647kHz Local Oscillators...................................................4-11
4.4.6 Clarifier .........................................................................................4-11
Issue 6
8525B/8528 Technical Service Manual
Publication No: 15-02036