Maxon Telecom SP210, SP200 service manual Audio/SAT Circuits

Page 32

Maxon SP200/210 Radio

SP200/210

5.4 Audio/SAT Circuits

CTCSS / DCS Decoder Circuits

Discriminator audio from pin 9 IC5 is applied, via IC408D, to pin 3 of the audio ASIC. The audio frequencies of the signal are filterecd out by the 7th order Elliptic Low Pass Filter, leaving only the SAT audio tones. The level is then set by the ASIC and is routed via IC407A back to the ASIC for comparison with a reference voltage. This produces the logic data signal. This logic signal on pin 21 (IC406) is fed into the microcontroller (IC403) where it is matched with a programmed frequency. If there is a successful match, decode occurs, which is shown by a green LED on the top of the radio and audio is heard. If there is an invalid decode, the LED will light yellow (BUSY)

CTCSS / DCS Encoder Circuits

During TX encode the tone squelch digital signal is produced as a 3-bit parallel word at pins 48, 49 and 50 of the micro controller (IC403). The 3-bit digital signal is converted to an analogue signal by resistors R420, 421 and 423. The analogue signal is fed into IC406 pin 4 where it is filtered and its deviation level is set.

The filtered encode output from pin 23 (IC406) is fed back into pin 22 (IC406) via IC407a (LM358). The filtered encode signal is mixed with the audio signal from TXTRIM1 by TXSUM. Via ATTN, the mixed signals are applied to TXTRIM2/TXTRIM3, which controls the modulation to the VCO and TCXO respectively (see RF description).

External Mic / PTT Control Circuit

The external microphone is connected via a 3.5 mm stereo jack socket on the right-hand side of the radio. The internal mic and speaker are disabled when the external connector is plugged the SPK/MIC jack socket.

When the external PTT is depressed, a low impedance is presented to the base of Q403 (below 20k ohm). Q402 and Q403 switch on and so Q402 collector is low (normally tied high). This point is connected to IC403 (microcontroller) pin 43 (PTT). The same point is connected to the normal PTT button, SW403, which is earthed when depressed.

The mic audio itself is switched through IC401A by the Tx enable line to IC408D amplifier stage and through to the audio ASIC for filtering and deviation level setting. As described previously, this audio signal is added to the SAT and routed to the TCXO and VCO.

Rx Audio

The discriminator audio is fed directly into the audio ASIC from the RF section (see later). The ASIC sets the gain and filters out any SAT. The output is fed to the volume control (VR5). The alert tones and switch on melody is routed from the microcontroller via link LK27 to the same point to the volume control.

The AF from the volume control is fed to the audio amplifier, a TDA7233, which is activated by the mute circuit. The output is then fed to the internal or external speaker.

Mute Circuit

The microcontroller (IC403) has a mute circuit which is output on pin 13 (7233EN). The operation of the mute depends upon a number of factors, such as is the demodulator receiving a mute signal from the FM detector and does the signal have the correct CTCSS / DCS. The microcontroller will also change the state of the mute if the monitor button is depressed (SW402), assuming that this function has been enabled in the programming

Pin 13 is connected to Q414, Q415 via R446, which mutes the TDA7233IC.

DETAILED FUNCTIONAL DESCRIPTION

Issue 1.0

Page 5-4

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 SL100 UHF Parts List 11.4 Default Settings 11-810-1 11-1List of Tables Maxon SP200/210 Radio Issue 03/01 Using this Manual IntroductionAmendments to this Manual Category C Engineering BulletinContact Information Specifications GeneralEnvironmental Operating Temperature Range Physical Dimensions SynthesiserVibration ESD EMCOptions Accessories & OptionsPre-Install Check Accessories Accessories & Options INSTALLATION, Commissioning & Alignment InstallationINSTALLATION, Commissioning & Alignment 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 Tests without Disassembly AlignmentPreparation 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% Detailed Functional Description Introduction Common Circuits EepromAudio Signal Path Audio AsicSat Signal Path Miscellaneous Signals and ControllerAudio/SAT Circuits Battery Low Indicator Circuit LEDs and indicatorsCommon RF Circuits PLL SynthesiserPLL IC Out-of-Lock DetectorCharge Pump and Loop Filter DC to DC ConverterAntenna Switch Automatic power control APC circuitsTransmitter PA moduleReceiver Front EndFirst Mixer Second mixer, Second IF, FM detectorSquelch Mute Circuit 16kHz Band Pass FilterSpeaker Audio Amplifier Noise detector circuitAF Output Low Pass Filter Troubleshooting Diagnostic FunctionDiagnostics TroubleshootingTroubleshooting Chart If ICMain Circuit Transistor Voltages Voltage ChartsTransistors Main Circuit Integrated Circuit Voltages Transmit Integrated CircuitsIntegrated Circuit Voltages Receive Troubleshooting Troubleshooting Troubleshooting Troubleshooting Programming SMP6100Introduction Getting StartedSelect Features Menu ScanningProgram/Print/Save Program RadioPrint Data Save Data to DiskMaxon SP200/200 Radio SP200/210 Exploded Mechanical Drawings & Parts Lists Parts ListExploded Mechanical Drawings & Parts Lists Spare PartsSL100U2 SL100V2Mechanical Parts For details on servicing, please refer to SectionParts List for Exploded Mechanical Drawing LCD TTR 1866 DpfdpwPCB LCD SKPT-110VASML-020MLTT86 SMD NUT M7 BsbmPCB VCO PCB RF Aldc Bsbm M2.605B-000-5Z SL100 VHF Parts ListV2 Control Circuit Diode Switching KDS181S A3 Chip Ceramic 0.001UF GRM39 X7R102K 50V PChip Ceramic 0.012UF GRM39 X7R123K 25V P Chip Ceramic 0.0022UF GRM39 X7R222J 50V P2 V2 RF SW Tact SKPT-1101VARES.CHIP Trimmer 1K RH03E1C13X RES.CHIP Trimmer 10K RH03E1C14XThermistor Chip 33KNTCCS32163SH333KC TH1 Elect Capacitor 10UF 16V 20%RE Power Module GNOK-M68776-E01 IC9 Chip Ceramic 39PF GRM40 COG390J 50V PChip Ceramic 43PF GRM40 COG430J 50V P Chip Ceramic 47PF GRM39 COG470J 50V PTcxo Assembly 4 V2 VCO 5 V2 Front EndSL100 UHF Parts List U2 Control CircuitConnector Waffer 2 U2 RF Chip Resistor 12KChip Resistor 18K Chip Resistor 39KRES.CHIP Trimmer K RH03E1C13X Chip Ceramic 0.0015UF GRM39 X7R152K 50V PChip Ceramic 10PF GRM40 COG100C 50V P Chip CeramicPower Mpduleuhf M68732HGNOK IC9 Chip Ceramic 2.2PF GRM40 COG2R2C 50V PChip Ceramic 470PF GRM40 COG471J 50V P Chip Ceramic 4.7PF GRM40 COG4R7C 50V PTcxo Coil Chip 18NHLL2012-F18NMCoil Spring X0.35X7TR Coil Spring 2X0.75X3TL SMD4 VCO Maxon SP200/210 Radio Circuit Diagrams & PCB Layouts Circuit Diagrams & PCB LayoutsRF PCB 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 Component Replacement Surface mount component replacementSurface mount components Surface mount removalSurface mounted integrated circuit replacement Spare Parts & Maintenance Policy 11APPENDIX ACC-2003 Alignment BOX 11.1Purpose11.2Test Equipment 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 Level11.4Default Settings 11.4.1 V1 Band Default SettingsV1 Default Frequency Table 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
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