The Marconi IFR Aeroflex T-33B Mode Transponder Test Set is a portable, battery-powered instrument for testing and calibrating aircraft transponders in the field or cockpit environment. Operating as a single-operator system, it simulates interrogation signals and analyzes transponder responses across civil and military modes while providing receiver sensitivity measurements and pulse timing verification.
Technical Specifications
Interrogation Signal
• Frequency: 1030 MHz
• Transmitter Accuracy: ±0.01% (crystal controlled)
Transponder Response Analysis
• Digital Readouts: Displays decoded reply in Pilot Code, Binary Code, and Altitude (feet)
• Altitude Display: Decimal point indicators show altitude presence
Receiver Sensitivity Measurement
• Direct connection via BNC connector to transponder
• IF Section Tuning Range: ±6 MHz
Side Lobe Suppression Testing
• SLS Pulse Level: Selectable at 9 dB below P1 and P3, or 0 dB (equal amplitude) for SLS circuit verification
• Response Meter: Displays transponder response percentage with automatic full-scale switching from 100% to 10% when SLS pulse is active
Pulse Characteristics
• Framing Pulse Delay Detection: Detects delays exceeding 3.5 microseconds after P3
Power
• Battery: Ni-Cad cells with built-in charger
– Key Features
• Supported Modes: Civil (A, B, C, D) and Military (1, 2, 3)
• Multiple display formats: Pilot Code, Binary Code, Altitude readout
• Video test point for oscilloscope analysis of interrogation and reply pulses
• Antenna connector for radiating interrogation signals
• Limited bench test capability via video output
– Typical Applications
• Operational transponder checks from aircraft cockpit
• Transponder calibration and verification
• SLS circuit validation
• Receiver sensitivity assessment
• Pulse timing and response verification
– Compatibility & Integration
The T-33B interfaces directly with transponders via antenna connection for signal radiation and BNC connector for direct receiver sensitivity measurements. Video test points enable oscilloscope-based analysis of signal characteristics.
