Nautel ND500II, Technical Instructions

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RADIOBEACON TRANSMITTER
ND500II (125 WATTS) DOUBLE SIDEBAND - NO VOICE
Contents (Page 1)
01 November 2003
TABLE OF CONTENTS
Section Page
1 GENERAL INFORMATION
1.1 INTRODUCTION ........................................................................................................ 1-1
1.2 PURPOSE AND SCOPE OF MANUAL ...................................................................... 1-1
1.3 PURPOSE OF EQUIPMENT ...................................................................................... 1-1
1.4 FACTORY REPAIR SERVICE .................................................................................... 1-5
1.5 MECHANICAL DESCRIPTION ................................................................................... 1-5
1.5.1 CABINET .................................................................................................................... 1-5
1.6 TECHNICAL SUMMARY ............................................................................................ 1-5
1.7 SPECIAL TOOLS AND TEST EQUIPMENT .............................................................. 1-5
1.8 GLOSSARY OF TERMS ............................................................................................ 1-5
2 THEORY OF OPERATION
2.1 GENERAL ................................................................................................................. 2-1
2.2 TRANSMITTER DESCRIPTION ................................................................................. 2-1
2.2.1 POWER SUPPLY (A1) ......................................................................................... 2-1
2.2.1.1 AC Power Source Operation........................................................................... 2-1
2.2.1.2 Unreg24V........................................................................................... 2-1
2.2.1.3 +15 Volt DC Regulator.................................................................................... 2-2
2.2.1.4 DC Power Source (Battery)............................................................................. 2-2
2.2.1.5 AC Monitoring................................................................................................. 2-2
2.2.1.6 B+ Monitoring/Inhibit....................................................................................... 2-3
2.2.2 OSCILLATOR/RF DRIVE PWB (A2)..................................................................... 2-3
2.2.2.1 Balance/RF Drive ........................................................................................... 2-3
2.2.3 KEYER PWB (A3) ................................................................................................ 2-3
2.2.4 MODULATOR DRIVER PWB (A4)........................................................................ 2-4
2.2.4.1 Mod Enable Switch ......................................................................................... 2-5
2.2.4.2 +15V to -15V Converter .................................................................................. 2-5
2.2.4.3 PWM Square Wave Generator ....................................................................... 2-5
2.2.4.4 PWM Ramp Integrator.................................................................................... 2-5
2.2.4.5 Variable Pulse-Width Generator ..................................................................... 2-5
2.2.4.6 Linear Attenuator ............................................................................................ 2-6
2.2.4.7 B+ Variation Compensation ............................................................................ 2-6
2.2.4.8 Low RF Drive Cutback.................................................................................... 2-6
2.2.4.9 Balanced Drive ............................................................................................... 2-7
2.2.4.10 Pulse-Width Fault Detector............................................................................. 2-7
2.2.5 POWER AMPLIFIER/MODULATOR (A6) ............................................................. 2-7
2.2.5.1 Modulator ....................................................................................................... 2-7
2.2.5.2 Power Amplifier .............................................................................................. 2-8
2.2.6 MONITOR PWB (A5)............................................................................................ 2-8
2.2.6.1 Forward Power/Fwd Pwr Cal........................................................................... 2-8
2.2.6.2 Audio Monitoring............................................................................................. 2-8
2.2.6.3 Monitor's +15V (A) Supply .............................................................................. 2-9
2.2.6.4 Low Carrier Level (-3dB) Detector................................................................... 2-9
2.2.6.5 High Carrier Level (+2dB) Detector................................................................. 2-9
2.2.6.6 Low Modulation Depth Detector ...................................................................... 2-9
2.2.6.7 Shutdown Control ......................................................................................... 2-10
2.2.6.8 Overmodulation Detector.............................................................................. 2-10