Transmitter, PA module, Low pass filter | Maxon Telecom SP200

SP200/210

Maxon SP200/210 Radio

5.6 Transmitter

The transmitter comprises:

Figure 5-3 - Transmitter Block Diagram

Buffer

The RF output level from the VCO is 0dBm. This is amplified to +17dBm by the buffer amplifier consisting of Q16, Q17, Q3 and associated components. All stages are simple common-emitter amplifiers with resistive biasing and tuned collectors. A pi-type attenuator (R31, 32 and 34) is used between the two stages.

PA module

The PA module consists of a hybrid amplifier. Pin 3 is permanently connected to the battery voltage and pin 2 is connected to the supply when switched by Q22, which is controlled via the power control circit by the Tx enable line. The RF input is on pin 1 and the output is on pin 4.

Low pass filter

L7, L8, L11, C73, C74, C75 and C76 form a 7th order Chebyshev low pass filter. Unwanted harmonics are reduced by 65dB.

Antenna Switch

When transmitting, the diodes D5 and D6 are forward biased, allowing the RF to pass to the antenna. D6 is shorted to ground which makes L13 look open circuit (1/4 wave tuned stub). This prevents the Tx signal from passing to the receiver stage.

In receive, the diodes D5 and D6 are reverse biased. L13 is now in circuit, passing the signal from the antenna to the front end without signal loss.

Automatic power control (APC) circuits

The APC circuit consists of IC3B, Q19, Q21, Q22 and associated components. The PA supply current passes through R109. Variations in power output, produce variations in supply current, which is amplified by IC3A and Q19.

The voltage on the wiper of RV1 is passed to IC3B and compared with the fixed reference voltage developed by the potential divider R45 and R46. The output of IC3B, pin 7, controls Q21 and Q22 to provide supply voltage to the PA driver transistors Q501 and Q502. RV3 controls the low power setting and is switched into circuit by Q23.

A change in PA output will result in an inverse change in driver supply voltage maintaining a constant RF output.

Issue 1.0	DETAILED FUNCTIONAL DESCRIPTION
03/01	Page 5-7

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Maxon Telecom SP200, SP210 Transmitter, PA module, Low pass filter, Antenna Switch, Automatic power control APC circuits

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 11-1 SL100 UHF Parts List11.4 Default Settings 11-8 10-1 List of Tables Maxon SP200/210 Radio Issue 03/01 Category C Engineering Bulletin Using this ManualIntroduction Amendments to this Manual Contact Information General Specifications ESD EMC Environmental Operating Temperature RangePhysical Dimensions Synthesiser Vibration Options Accessories & OptionsPre-Install Check Accessories Accessories & Options Connections INSTALLATION, Commissioning & AlignmentInstallation INSTALLATION, Commissioning & Alignment Recommended Test Equipment Commissioning Commissioning Kit Commissioning Equipment Discrete Test Equipment Test Equipment Set-up using Discrete Test Equipment SK 3100 Service Kit Receiver Performance Tests Test Equipment ConnectionTransmitter Performance Tests Audio Output Power AdjustmentSquelch VHF Tests without DisassemblyAlignment Preparation 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% Eeprom Detailed Functional DescriptionIntroduction Common Circuits Audio Asic Audio Signal Path Miscellaneous Signals and Controller Sat Signal Path Audio/SAT Circuits PLL Synthesiser Battery Low Indicator CircuitLEDs and indicators Common RF Circuits DC to DC Converter PLL ICOut-of-Lock Detector Charge Pump and Loop Filter PA module Antenna SwitchAutomatic power control APC circuits Transmitter Front End Receiver 16kHz Band Pass Filter First MixerSecond mixer, Second IF, FM detector Squelch Mute Circuit Speaker Audio Amplifier Noise detector circuitAF Output Low Pass Filter Troubleshooting TroubleshootingDiagnostic Function Diagnostics If IC Troubleshooting Chart Main Circuit Transistor Voltages Voltage ChartsTransistors Main Circuit Integrated Circuit Voltages Transmit Integrated CircuitsIntegrated Circuit Voltages Receive Troubleshooting Troubleshooting Troubleshooting Troubleshooting Getting Started ProgrammingSMP6100 Introduction Program Radio Select Features MenuScanning Program/Print/Save Save Data to Disk Print Data Maxon SP200/200 Radio SP200/210 Spare Parts Exploded Mechanical Drawings & Parts ListsParts List Exploded Mechanical Drawings & Parts Lists SL100V2 SL100U2 For details on servicing, please refer to Section Mechanical Parts LCD TTR 1866 Dpfdpw Parts List for Exploded Mechanical Drawing NUT M7 Bsbm PCB LCDSKPT-110VA SML-020MLTT86 SMD PCB VCO PCB RF Bsbm M2.6 Aldc 05B-000-5Z SL100 VHF Parts ListV2 Control Circuit Chip Ceramic 0.0022UF GRM39 X7R222J 50V P Diode Switching KDS181S A3Chip Ceramic 0.001UF GRM39 X7R102K 50V P Chip Ceramic 0.012UF GRM39 X7R123K 25V P SW Tact SKPT-1101VA 2 V2 RF Elect Capacitor 10UF 16V 20% RES.CHIP Trimmer 1K RH03E1C13XRES.CHIP Trimmer 10K RH03E1C14X Thermistor Chip 33KNTCCS32163SH333KC TH1 Chip Ceramic 47PF GRM39 COG470J 50V P RE Power Module GNOK-M68776-E01 IC9Chip Ceramic 39PF GRM40 COG390J 50V P Chip Ceramic 43PF GRM40 COG430J 50V P Tcxo Assembly 5 V2 Front End 4 V2 VCO U2 Control Circuit SL100 UHF Parts List Connector Waffer Chip Resistor 39K 2 U2 RFChip Resistor 12K Chip Resistor 18K Chip Ceramic RES.CHIP Trimmer K RH03E1C13XChip Ceramic 0.0015UF GRM39 X7R152K 50V P Chip Ceramic 10PF GRM40 COG100C 50V P Chip Ceramic 4.7PF GRM40 COG4R7C 50V P Power Mpduleuhf M68732HGNOK IC9Chip Ceramic 2.2PF GRM40 COG2R2C 50V P Chip Ceramic 470PF GRM40 COG471J 50V P Coil Spring 2X0.75X3TL SMD TcxoCoil Chip 18NHLL2012-F18NM Coil Spring X0.35X7TR 4 VCO Maxon SP200/210 Radio Tcxo Circuit Diagrams & PCB LayoutsCircuit Diagrams & PCB Layouts RF PCB 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 removal Component ReplacementSurface mount component replacement Surface mount components Surface mounted integrated circuit replacement Spare Parts & Maintenance Policy 11.3Calibration Program 11APPENDIX ACC-2003 Alignment BOX11.1Purpose 11.2Test Equipment Appendix a ACC-2003 Alignment BOX Calibration Program Primary Screen Asic Control Screen Rx TXTRIM3 Adjustment of Asic valuesTXTRIM2 RX VOL SAT Deviation Transmit AdjustmentsSAT Balance Audio Output Level Receive Adjustments V1 Default Asic Settings 11.4Default Settings11.4.1 V1 Band Default Settings V1 Default Frequency Table 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