Noise detector circuit | Maxon Telecom SP210, SP200 specs

Maxon SP200/210 Radio

SP200/210

Noise detector circuit

The noise detector circuit, in conjunction with IC5, consists of transistors Q26, Q27, thermistor TH1 and diode D11. Any noise signal present is applied to Q27 from pin 11 of IC5. The signal is amplified by Q27, rectified by D11 and then buffered by Q26. The buffered signal is applied to pin 12 of IC5 (Squelch input).

The squelch trigger output (pin 14, IC5) is applied to the microcontroller BUSY input on pin 54 of IC403. The actual audio mute is from the microcontroller.

When noise is present, the voltage at pin 12 of IC5 (Squelch input) exceeds 0.7V. This causes the squelch trigger output to go open circuit, which turns on Q24 and the busy line goes low, which mutes the receiver audio circuit.

When no noise is present, the voltage at pin 12 of IC5 is less than 0.7 V and pin 14 of IC5 is grounded, which switches Q24 off, so the busy line goes high, unmuting the receiver audio circuit. Resistor R74 is used to provide hysteresis of 3 to 6 dB.

AF Output Low Pass Filter

A low pass filter formed by C115, C116 and R91 removes any extraneous 455 kHz energy from the AF output of the FM receiver chip.

Speaker Audio Amplifier

After signal detection and audio filtering the signal is passed to the digital board, to the audio ASIC (via IC408 for SAT). ). After the audio ASIC (see previous description) the signal is then routed, via the volume control (VR5), to pin 8 of IC402. IC402 is a TDA7233 audio amplifier, which is enabled by the control line from the microcontroller via Q415 and Q414.

DETAILED FUNCTIONAL DESCRIPTION	Issue 1.0
Page 5-10	03/01

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Maxon Telecom SP210, SP200 service manual Noise detector circuit, AF Output Low Pass Filter, Speaker Audio Amplifier

Contents

SP200/210 NSW Australia Tel +61 0 2 9707 Amendment Record Sheet Issue No Effective Date Reason for Change SignatureAmendment Record Sheet Maxon SP200/210 Radio Table of Contents 10-1 SL100 UHF Parts List11.4 Default Settings 11-8 11-1 List of Tables Maxon SP200/210 Radio Issue 03/01 Amendments to this Manual Using this ManualIntroduction Category C Engineering Bulletin Contact Information Specifications General Vibration Environmental Operating Temperature RangePhysical Dimensions Synthesiser ESD EMC Options Accessories & OptionsPre-Install Check Accessories Accessories & Options INSTALLATION, Commissioning & Alignment INSTALLATION, Commissioning & AlignmentInstallation Connections Commissioning Recommended Test Equipment Commissioning Equipment Commissioning Kit Test Equipment Set-up using Discrete Test Equipment Discrete Test Equipment SK 3100 Service Kit Receiver Performance Tests Test Equipment ConnectionTransmitter Performance Tests Audio Output Power AdjustmentSquelch Preparation Tests without DisassemblyAlignment VHF Removing and Replacing the Belt Clip Disassembly and Re-assembly of the RadioRemoving and Replacing Battery PLL Alignment Removing and Replacing the Main AssemblyLocation of Adjustment Points Tcxo Squelch SensitivityTransmitter Alignment Radiocommunications Test SET Ctcss / DCS deviation Balance AdjustmentAudio deviation adjustment Receiver Alignment Audio Volume LevelAt maximum volume, nominal distortion is 10% Common Circuits Detailed Functional DescriptionIntroduction Eeprom Audio Signal Path Audio Asic Sat Signal Path Miscellaneous Signals and Controller Audio/SAT Circuits Common RF Circuits Battery Low Indicator CircuitLEDs and indicators PLL Synthesiser Charge Pump and Loop Filter PLL ICOut-of-Lock Detector DC to DC Converter Transmitter Antenna SwitchAutomatic power control APC circuits PA module Receiver Front End Squelch Mute Circuit First MixerSecond mixer, Second IF, FM detector 16kHz Band Pass Filter Speaker Audio Amplifier Noise detector circuitAF Output Low Pass Filter Diagnostics TroubleshootingDiagnostic Function Troubleshooting Troubleshooting Chart If IC Main Circuit Transistor Voltages Voltage ChartsTransistors Main Circuit Integrated Circuit Voltages Transmit Integrated CircuitsIntegrated Circuit Voltages Receive Troubleshooting Troubleshooting Troubleshooting Troubleshooting Introduction ProgrammingSMP6100 Getting Started Program/Print/Save Select Features MenuScanning Program Radio Print Data Save Data to Disk Maxon SP200/200 Radio SP200/210 Exploded Mechanical Drawings & Parts Lists Exploded Mechanical Drawings & Parts ListsParts List Spare Parts SL100U2 SL100V2 Mechanical Parts For details on servicing, please refer to Section Parts List for Exploded Mechanical Drawing LCD TTR 1866 Dpfdpw SML-020MLTT86 SMD PCB LCDSKPT-110VA NUT M7 Bsbm PCB VCO PCB RF Aldc Bsbm M2.6 05B-000-5Z SL100 VHF Parts ListV2 Control Circuit Chip Ceramic 0.012UF GRM39 X7R123K 25V P Diode Switching KDS181S A3Chip Ceramic 0.001UF GRM39 X7R102K 50V P Chip Ceramic 0.0022UF GRM39 X7R222J 50V P 2 V2 RF SW Tact SKPT-1101VA Thermistor Chip 33KNTCCS32163SH333KC TH1 RES.CHIP Trimmer 1K RH03E1C13XRES.CHIP Trimmer 10K RH03E1C14X Elect Capacitor 10UF 16V 20% Chip Ceramic 43PF GRM40 COG430J 50V P RE Power Module GNOK-M68776-E01 IC9Chip Ceramic 39PF GRM40 COG390J 50V P Chip Ceramic 47PF GRM39 COG470J 50V P Tcxo Assembly 4 V2 VCO 5 V2 Front End SL100 UHF Parts List U2 Control Circuit Connector Waffer Chip Resistor 18K 2 U2 RFChip Resistor 12K Chip Resistor 39K Chip Ceramic 10PF GRM40 COG100C 50V P RES.CHIP Trimmer K RH03E1C13XChip Ceramic 0.0015UF GRM39 X7R152K 50V P Chip Ceramic Chip Ceramic 470PF GRM40 COG471J 50V P Power Mpduleuhf M68732HGNOK IC9Chip Ceramic 2.2PF GRM40 COG2R2C 50V P Chip Ceramic 4.7PF GRM40 COG4R7C 50V P Coil Spring X0.35X7TR TcxoCoil Chip 18NHLL2012-F18NM Coil Spring 2X0.75X3TL SMD 4 VCO Maxon SP200/210 Radio RF PCB Circuit Diagrams & PCB LayoutsCircuit Diagrams & PCB Layouts Tcxo Circuit Diagrams & PCB Layouts Digital Board Layout Top Side Digital Board Layout Bottom Side RF Board Layout Top Side Issue RF Board Layout Bottom Side P406787a Front End Front-End Board Layout Tcxo Board Layout 10.1Spare Parts Spare Parts & Maintenance Policy10SPARE Parts Surface mount components Component ReplacementSurface mount component replacement Surface mount removal Surface mounted integrated circuit replacement Spare Parts & Maintenance Policy 11.2Test Equipment 11APPENDIX ACC-2003 Alignment BOX11.1Purpose 11.3Calibration Program Calibration Program Primary Screen Appendix a ACC-2003 Alignment BOX Asic Control Screen Rx TXTRIM3 Adjustment of Asic valuesTXTRIM2 RX VOL SAT Deviation Transmit AdjustmentsSAT Balance Receive Adjustments Audio Output Level V1 Default Frequency Table 11.4Default Settings11.4.1 V1 Band Default Settings V1 Default Asic Settings V2 Default Asic Settings 11.4.2 V2 Band Default SettingsV2 Default Frequency Table U1 Default Asic Settings 11.4.3 U1 Band Default SettingsU1 Default Frequency Table U2 Default Asic Settings 11.4.4 U2 Band Default SettingsU2 Default Frequency Table