Agilent/Keysight N9961B

The Keysight N9961B FieldFox is a portable handheld RF analyzer delivering spectrum analysis, vector network analysis, and cable/antenna characterization across 9 kHz to 44 GHz. Built for field service technicians and RF engineers, it combines ±0.2 dB amplitude accuracy with real-time spectrum analysis up to 120 MHz gap-free bandwidth. The instrument captures intermittent signals and supports interference detection, noise figure measurement, EMI analysis, and pulse characterization through configurable software options.

VNA capabilities enable full 2-port reflection and transmission measurements, while time-domain reflectometry and TDR cable analysis pinpoint faults in transmission lines. Optional over-the-air measurement modes support 5G NR and LTE characterization. GPS/GNSS geolocation, I/Q data capture, and indoor/outdoor mapping extend utility for field deployment and drive-test applications.

Technical Specifications

• 9 kHz to 44 GHz (usable down to 5 kHz) Amplitude Performance:


• Amplitude accuracy: ±0.2 dB overall (typical)


• Display average noise level (DANL): −163 dBm @ 2 GHz; −154 dBm typical


• Third-order intercept (TOI) @ 1 GHz: +5.1 dBm


• Spur-free dynamic range: >104 dB


• Output power: up to 6 dBm typical Spectral Purity:


• Phase noise @ 1 GHz: - 1 MHz offset: −125 dBc/Hz - 10 kHz offset: −114 dBc/Hz - 30 kHz offset: −114 dBc/Hz Attenuation:


• Standard attenuator range: 40 dB


• Standard attenuator step: 5 dB

Key Features

• Real-time spectrum analysis with 120 MHz gap-free bandwidth


• Intermittent signal capture and spectrogram analysis


• Full 2-port VNA with return loss and VSWR measurement


• Time-domain reflectometry for cable characterization


• Analog demodulation (AM/FM) and tune-and-listen capability


• Field strength, noise figure, and EMI measurement modes


• Over-the-air 5G NR and LTE analysis


• I/Q data streaming and signal monitoring


• GPS/GNSS receiver with geolocation and timestamping


• Field-swappable battery architecture

Typical Applications

• RF/microwave system maintenance and troubleshooting


• Communication system commissioning and site surveys


• Radar and electronic warfare signal characterization


• Antenna and transmission line fault location


• EMI/RFI source identification and mapping


• 5G and LTE network drive testing

Compatibility & Integration

• USB power sensor support


• I/Q streaming for external signal processing


• Channel scanner and extended range transmission analysis modes


• GPS/GNSS integration for temporal and spatial correlation