The Keysight N9951B FieldFox is a handheld microwave combination analyzer engineered for field deployment in aerospace, defense, and wireless communications environments. This ruggedized 3.4 kg instrument integrates spectrum analysis, cable and antenna testing, and power measurements into a single platform. The N9951B operates across 9 kHz to 44 GHz (spectrum analysis) and 300 kHz to 44 GHz (cable/antenna), with optional vector network analysis extending capability to 44 GHz. The base unit delivers spectrum measurements accurate to ±0.2–0.3 dB without warm-up and supports real-time bandwidth to 120 MHz gap-free analysis. Built-in ports number two; system dynamic range reaches 105 dB.
Technical Specifications
Physical & Environmental
• Weight: 3.4 kg (7.4 lb)
• Operating temperature: −10 to +55 °C
• IP rating: IP53 per IEC/EN 60529
• Ruggedness: MIL-PRF-28800F Class 2 and MIL-STD-810G Method 511.5 for explosive environments
Frequency Coverage
• Spectrum analyzer: 9 kHz to 44 GHz
• Cable/antenna analyzer: 300 kHz to 44 GHz
• Over-the-air analysis: 1 MHz to 44 GHz (usable to 5 kHz)
Measurement Performance
• Spectrum analysis accuracy: ±0.2–0.3 dB (no warm-up required)
• Real-time bandwidth: 120 MHz gap-free
• Minimum signal duration for 100% POI at full amplitude: 5.52 µs
• VNA dynamic range: 105–115 dB (optional)
– Key Features
• Two-port vector network analysis with simultaneous S-parameter measurement (optional)
• Cable and antenna testing with DTF, return loss, and VSWR measurements
• Built-in time-domain reflectometry (TDR) via option
• Over-the-air capabilities for 5G NR and LTE
• Optional noise figure measurements
• Independent signal generator
• Integrated GPS/GNSS receiver for geolocation and timestamping
• Calibration methods: CalReady, OSL, Response, Enhanced Response
• Vector voltmeter functionality
– Typical Applications
• Field RF and microwave testing
• Cable and transmission line characterization
• Antenna performance verification
• 5G signal analysis
• Interference detection and analysis
• Network parameter verification in aerospace and defense
– Compatibility & Integration
The N9951B accepts software options to enable advanced functions including vector network analysis, time-domain reflectometry, pulse measurement, and extended-range transmission analysis. Analog demodulation and spectrogram capabilities are available through configuration. The instrument’s dual-port architecture supports mixed-mode S-parameter measurements and vector voltmeter operation.
