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

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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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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 11-1List of Tables Maxon SP200/210 Radio Issue 03/01 Amendments to this Manual Using this ManualIntroduction Category C Engineering BulletinContact Information Specifications GeneralVibration Environmental Operating Temperature RangePhysical Dimensions Synthesiser ESD EMCOptions Accessories & OptionsPre-Install Check Accessories Accessories & Options INSTALLATION, Commissioning & Alignment INSTALLATION, Commissioning & AlignmentInstallation ConnectionsCommissioning Recommended Test EquipmentCommissioning Equipment Commissioning KitTest Equipment Set-up using Discrete Test Equipment Discrete Test EquipmentSK 3100 Service Kit Receiver Performance Tests Test Equipment ConnectionTransmitter Performance Tests Audio Output Power AdjustmentSquelch Preparation Tests without DisassemblyAlignment VHFRemoving 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 EepromAudio Signal Path Audio AsicSat Signal Path Miscellaneous Signals and ControllerAudio/SAT Circuits Common RF Circuits Battery Low Indicator CircuitLEDs and indicators PLL SynthesiserCharge Pump and Loop Filter PLL ICOut-of-Lock Detector DC to DC ConverterTransmitter Antenna SwitchAutomatic power control APC circuits PA moduleReceiver Front EndSquelch Mute Circuit First MixerSecond mixer, Second IF, FM detector 16kHz Band Pass FilterSpeaker Audio Amplifier Noise detector circuitAF Output Low Pass Filter Diagnostics TroubleshootingDiagnostic Function TroubleshootingTroubleshooting Chart If ICMain Circuit Transistor Voltages Voltage ChartsTransistors Main Circuit Integrated Circuit Voltages Transmit Integrated CircuitsIntegrated Circuit Voltages Receive Troubleshooting Troubleshooting Troubleshooting Troubleshooting Introduction ProgrammingSMP6100 Getting StartedProgram/Print/Save Select Features MenuScanning Program RadioPrint Data Save Data to DiskMaxon SP200/200 Radio SP200/210 Exploded Mechanical Drawings & Parts Lists Exploded Mechanical Drawings & Parts ListsParts List Spare PartsSL100U2 SL100V2Mechanical Parts For details on servicing, please refer to SectionParts List for Exploded Mechanical Drawing LCD TTR 1866 DpfdpwSML-020MLTT86 SMD PCB LCDSKPT-110VA NUT M7 BsbmPCB VCO PCB RF Aldc Bsbm M2.605B-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 P2 V2 RF SW Tact SKPT-1101VAThermistor 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 PTcxo Assembly 4 V2 VCO 5 V2 Front EndSL100 UHF Parts List U2 Control CircuitConnector Waffer Chip Resistor 18K 2 U2 RFChip Resistor 12K Chip Resistor 39KChip Ceramic 10PF GRM40 COG100C 50V P RES.CHIP Trimmer K RH03E1C13XChip Ceramic 0.0015UF GRM39 X7R152K 50V P Chip CeramicChip Ceramic 470PF GRM40 COG471J 50V P Power Mpduleuhf M68732HGNOK IC9Chip Ceramic 2.2PF GRM40 COG2R2C 50V P Chip Ceramic 4.7PF GRM40 COG4R7C 50V PCoil Spring X0.35X7TR TcxoCoil Chip 18NHLL2012-F18NM Coil Spring 2X0.75X3TL SMD4 VCO Maxon SP200/210 Radio RF PCB Circuit Diagrams & PCB LayoutsCircuit Diagrams & PCB Layouts TcxoCircuit 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 removalSurface mounted integrated circuit replacement Spare Parts & Maintenance Policy 11.2Test Equipment 11APPENDIX ACC-2003 Alignment BOX11.1Purpose 11.3Calibration ProgramCalibration Program Primary Screen Appendix a ACC-2003 Alignment BOXAsic Control Screen Rx TXTRIM3 Adjustment of Asic valuesTXTRIM2 RX VOL SAT Deviation Transmit AdjustmentsSAT Balance Receive Adjustments Audio Output LevelV1 Default Frequency Table 11.4Default Settings11.4.1 V1 Band Default Settings V1 Default Asic SettingsV2 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