# Keysight N9937D FieldFox 18 GHz Handheld Spectrum Analyzer # Keysight N9937D FieldFox 18 GHz Handheld Spectrum Analyzer ## Key Features At A Glance - Frequency coverage options from 4 GHz up to 54 GHz across the FieldFox handheld analyzer family - Ruggedized handheld form factor at 7.5 lb (3.4 kg), MIL-PRF-28800F Class 2, MIL-STD-810G Method 511.5 Procedure I, and IEC/EN 60529 ingress protection - Field-swappable battery operation up to 4 hours, with operating temperature range of -10 to +55 °C - Combination analyzer architecture covering Cable and Antenna Test (CAT), Spectrum Analysis, and Vector Network Analysis from a single handheld instrument - Up to 120 MHz analysis bandwidth available via Option B10 for wideband signal analysis and IQ data streaming - Built-in GNSS/GPS receiver for geolocation tagging and external frequency reference - Optional Real-Time Spectrum Analyzer (RTSA) capability for capturing intermittent and burst RF events - Optional built-in pulse generator extends the handheld analyzer from signal analysis to signal generation up to 54 GHz The Keysight FieldFox Handheld Analyzer is a ruggedized, battery-powered handheld test instrument designed for RF and microwave measurements outside the laboratory environment. The FieldFox family covers frequency ranges from 4 GHz through 54 GHz across multiple model variants, and each unit is built to withstand harsh working conditions while delivering measurement performance the datasheet positions as correlating with high-performance benchtop instruments. The instrument is intended as a field-capable platform for measuring cables, antennas, filters, amplifiers, and modulated RF signals. FieldFox is positioned by the datasheet for cable and antenna test on cellular and microwave infrastructure, 5G deployment and field testing, satellite and radar coverage verification, beamforming verification with phased array antennas, radar and electronic warfare systems diagnostics, and field signal monitoring with wideband IQ capture. The datasheet specifically identifies hardware installation and maintenance, over-the-air signal quality verification, interference hunting, and characterization of pulsed RF signals as application areas the instrument is designed to address. ValueTronics stocks and tests the FieldFox handheld analyzer family at our 20,000 square foot secure warehouse at 1675 Cambridge Drive in Elgin, Illinois. Every unit we list passes through our in-house performance verification process before shipping, and our condition reports document what our technicians measured rather than what a prior seller described. We have been supplying test and measurement instruments to engineering teams, defense programs, university labs, and field service operations since 1992, and our breadth across more than 120 manufacturers means we can pair a FieldFox with the cables, calibration kits, antennas, and companion instruments a complete field measurement setup typically requires. ## Brand Heritage Keysight Technologies was spun off from Agilent Technologies in 2014, and Agilent itself was created in 1999 when Hewlett-Packard separated its test and measurement business from its computing business. The HP–Agilent–Keysight progression means that FieldFox is a direct continuation of the Hewlett-Packard test and measurement engineering legacy, and calibration support, application engineering, and the broader product ecosystem are now provided under the Keysight name. ## Compare Other Models in This Series The FieldFox family is organized into two parallel product lines that share the same handheld chassis and user interface. Combination analyzer models — covering Cable and Antenna Test, Vector Network Analysis, and Spectrum Analysis — use model numbers in the N991x, N993x, N995x, and N912C ranges. Dedicated Spectrum Analyzer models use model numbers in the N993x, N996x, and corresponding C-series ranges. Both lines span frequency coverage from 4 GHz through 54 GHz, allowing a buyer to match the instrument's frequency ceiling to the highest frequency the application requires. Across the family, the datasheet identifies three series generations: the legacy B-Series (now discontinued for several models and replaced by the C-Series equivalents), the current C-Series, and the newly introduced D-Series. The D-Series adds 120 MHz IQ streaming bandwidth, a Linux operating system, SFP+ 10-Gigabit Ethernet interfaces, a touchscreen for file management, and an enhanced DC power supply output. The C-Series N9912C in particular is positioned as a fully software-defined analyzer whose frequency coverage and instrument personality (CAT, VNA, or SA) are selected at purchase and upgradable by software license. Each FieldFox model on this page is its own product listing with condition-matched pricing. Every new FieldFox unit is selected and prepared per the condition standards described on the listing, and the model variants in the comparison table below reflect the different frequency ceilings and feature sets available across the family. The most consequential difference between FieldFox models is the maximum frequency. The N991x and N993x combination and spectrum analyzer models cover up to 4, 6.5, 9, 10, 14, 18, and 26.5 GHz. The N995x and N996x models extend coverage to 32, 44, 50, and 54 GHz, with the highest-frequency 54 GHz models (N9953 and N9963) using 1.85 mm test port connectors. The 26.5 GHz N9918 and N9938 models, and the 32 GHz and above models, use 2.4 mm or 1.85 mm connectors; lower-frequency models in the family use Type-N (female) or 3.5 mm (male) test ports as printed on each model's port labeling. Beyond frequency coverage, models differ in their base instrument personality. Combination analyzers (N991x, N993x, N995x at the top of each frequency tier) include CAT and VNA capability as the base function with spectrum analysis available as an option. Dedicated spectrum analyzer models (N993x, N996x in the lower row of each frequency tier) include spectrum analysis as the base function and do not include the full VNA personality, although Option 320 provides reflection measurements including return loss and VSWR. The C-Series N9912C uniquely allows the buyer to choose CAT, NA, and/or SA personalities at the time of purchase through the CA, NA, and SA option codes, with frequency upgrade available via the N9912CU upgrade product. Model Max Frequency Type Series **N9937D** 18 GHz Spectrum Analyzer D-Series N9912C 4 / 6.5 / 10 GHz (configurable) Combination Analyzer (Software-Defined) C-Series N9913C 4 GHz Combination Analyzer C-Series N9914C 6.5 GHz Combination Analyzer C-Series Additional differences in specifications beyond the few shown above are not listed here — see each model's full specifications below. ## Product Core & Specifications Specification Value General — Physical Weight 7.5 lb. (3.4 kg) Dimensions (W x H) 7.4 in. (188 mm) x 11.5 in. (292 mm) Display Anti-glare 6.5-inch LCD with LED backlight Touchscreen (D-Series) Yes, for file management Environmental Operating temperature \-10 to +55 ºC (14 to 131 ºF) Ruggedization MIL-PRF-28800F Class 2 Explosive environment MIL-STD-810G, Method 511.5, Procedure I (type tested) Ingress protection IEC/EN 60529 (type tested) Battery / Power Battery life Up to 4 hours (field swappable); up to 4.5 hours per datasheet pages 7, 9 Vector Network Analyzer (VNA) Frequency range 3 / 30 / 300 kHz to 54 GHz System dynamic range 117 dB Trace noise 0.001 dB Directivity 39 dB Output power 9 dBm Calibrations CalReady, SOLT, WG, Unknown thru, Response Cal, ECal Spectrum Analyzer (SA) Frequency range 3 / 5 kHz to 54 GHz Spur-free dynamic range \>104 dB at 2.4 GHz Amplitude accuracy 0.2 dB Phase noise \-117 dBc/Hz DANL (preamp on) \-163 dBm CW/Tracking generator 5 / 30 / 300 kHz to 54 GHz Input related spur \-80 dBm TOI +13 dBm @ 2.4 GHz Connectivity RF connectors Type-N (f), 3.5 mm (m), 2.4 mm (m), or 1.85 mm (m) depending on model LAN Yes (data transfer and SCPI programming) USB USB ports (data storage / SCPI). D-Series: Type C USB 3.0/DP out and Type A USB 3.0 SFP+ (D-Series only) Two SFP+ hot-pluggable sockets, 10-GbE compliant SD card slot Yes External reference / trigger Input and output GPS/GNSS Built-in receiver Warranty Standard warranty 3-year (5-, 7-, and 10-year warranties also available) **Important:** Maximum input rating: +27 dBm RF, 50 VDC max on N991x/3x and N9938 (without Option 100); +25 dBm RF, 40 VDC max on N995x/6x and on N9918/N9938 with Option 100. Confirm the input limit for the specific model and option configuration before connecting to a high-power source.**Important:** B-Series models marked with an asterisk (N9913B, N9914B, N9915B, N9933B, N9934B, N9935B) are discontinued and replaced by the corresponding N99xxC models per the datasheet cover.**Important:** N9912C main chassis must be configured with at least one option from the Instrument Options group (CA4/CA6/CAX, NA4/NA6/NAX, or SA4/SA6/SAX). Do not pick two options from the same instrument group.**Important:** Cable and Antenna Test (CAT) is not available on the N993x/6xB Spectrum Analyzer models; a subset (return loss and VSWR) is available as Option 320.**Important:** Option 320 is not available on either C models or D models.**Important:** On the N991x/5xB,D analyzers there is no Option 220 — order Options 233 and 210 to obtain a tracking generator with the spectrum analyzer.**Important:** Calibration kits, ECal modules, and USB power sensors are sold separately and may be required to perform the calibrations and power measurements described in this technical overview.**Important:** EMF measurement functionality requires connection to an external triaxial isotropic antenna such as the AGOS Advanced Technologies or Keysight 85572A (sold separately).**Important:** Direction Finding (AoA) requires a compatible handheld directional antenna such as the Keysight 85573A or 85574A (sold separately).**Important:** TDOA direction finding requires three or four FieldFox analyzers networked together plus the Keysight Spectrum Management Software (KSMS) running on a separate Windows PC.Recommended pairing: FieldFox supports Keysight USB ECal modules for fast, accurate vector network analyzer calibration, and connects to Keysight USB power sensors for RF and microwave power and pulse measurements. For wideband signal analysis, the IF output streams to PathWave 89600 VSA software over LAN. **Please review the Manufacturer's Data Sheet to verify published specifications. Feedback on this webpage is always welcome — please reach out to your Test Architect at any time for questions or concerns. Thank you, we truly appreciate you being our customer.** ## Details - **Price:** 39287.0 USD - **Vendor:** Keysight - **Type:** Spec An - **Tags:** 10 GbE SFP+, 120 MHz Bandwidth, 18 GHz, 5G Field Test, Analyzers, Cable and Antenna, FieldFox, FieldFox 993xD, Handheld Analyzer, IP53, Keysight, Keysight FieldFox D-Series, Keysight Technologies, Linux OS, Manufacturers, Microwave Analyzer, MIL-PRF-28800F, Model_N9937D, Portable Analyzer, product_manual_group_3, Product_new, RF Analyzer, Series_993xD, Signal Analyzer, Spectrum, Spectrum Analyzer, Updated Item Review, Upgradable Option ## Variants | Variant | Price | Available | |---------|-------|-----------| | Default Title | 39287.00 USD | In stock | ## Images - Keysight N9937D FieldFox 18 GHz Handheld Spectrum Analyzer - Keysight N9937D FieldFox 18 GHz Handheld Spectrum Analyzer - Keysight N9937D FieldFox 18 GHz Handheld Spectrum Analyzer - Keysight N9937D FieldFox 18 GHz Handheld Spectrum Analyzer --- > Source: [ValueTronics](https://valuetronics.com/products/n9937d-new-keysig-cabant-ana-new) > Updated: 2026-05-30