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A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11The Keysight 8720C is an obsolete HP/Agilent-era two-port microwave vector network analyzer covering approximately 50 MHz to 20 GHz. It remains useful for conventional S-parameter work, but only when the exact options, connector condition, calibration state and performance near 20 GHz are verified. Keysight now directs buyers to newer instruments such as the P5004B Streamline VNA and E5080B ENA.
What the 8720C is
The 8720C is a benchtop vector network analyzer (VNA) for measuring complex scattering parameters in RF and microwave components. It integrates a synthesized source, tuned receiver, switching test set and color display rather than relying on a separate source and receiver. The model belongs to the HP and Agilent product lineage that preceded the Keysight brand.
Keysight lists the product as obsolete; it is not a current-production analyzer. The official product page is Keysight’s 8720C page.
Core specifications
| Specification | Reported value | Qualification |
|---|---|---|
| Instrument type | Two-port microwave VNA | Integrated source, receiver and test set |
| Frequency range | 50 MHz–20 GHz | Keysight’s description; verify each unit’s configuration and test status |
| Measurements | S11, S21, S12 and S22 | Four S-parameters can be obtained with the integrated switching configuration |
| Frequency resolution | 1 Hz optional | Option 001; resolution is not the same as accuracy or dynamic range |
| Display | Integrated color display | Original displays and conversions are significant used-equipment risks |
| Source | Fast-sweeping synthesized source | Official product description |
| Time-domain capability | Optional | Option 010; not a modern dedicated TDR |
| Test-set switching | Optional solid-state switching | Option 006; configuration-dependent |
| Product status | Obsolete | No longer current production |
Some secondary listings claim a 130 MHz lower limit or give dynamic-range values in incorrect units. Keysight’s 50 MHz–20 GHz description is the appropriate headline specification, but the serial-number-specific configuration and calibration condition still matter. Do not quote one maximum dynamic-range figure without the original data sheet for the exact options and test conditions.
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- [UPGRADED NanoVNA-H] New HW Version V3.7. It is upgradeable as new firmware is developed. With MicroSD card port now can have the measurement data or the screenshots saved in the it at anytime. Added battery circuit management, more secure. Redesigned PCB, you can connect to mobile phone with Type C-Type C cable (original PCB needs OTG cable), see a clear HD image on your phone. Added a ABS case, which is protective and dust-proof. Disply: 2.8 inch TFT (320 x240).
- [IMPROVED FREQUENCY ALGORITHM] The improved frequency algorithm can use the odd harmonic extension of si5351 to support the measurement frequency up to 1.5GHz. The 9KHz-300MHz frequency range of the si5351 direct output provides better than 70dB dynamic, The extended 300M-900MHz band provides better than 60dB of dynamics, and the 900M-1.5GHz band is better than 40dB of dynamics.
- [MULTIPLE FUNCTIONS] The default firmware main function is used for antenna performance measurement. The TX/RX method can measure the complete S11 and S21 parameters. If you need to obtain S12 and S22, you need to manually replace the transceiver port wiring. The CH0 output level is increased to 0dBm when using the fundamental wave, resulting in more accurate reflection measurement.
- [SUPPORT ANDROID PHONE & PC SOFTSARE CONTROL] Designed a practical and simple control application on PC, you can download touchstone(SNP) files for radio design and simulation software. There is a PC interface that adds functionality and lets you work interactively on a bigger screen. Supports time domain analysis function (TDR). Compatible with most Android mobile phones, convenient for connecting to mobile phones. Support Windows Computer Control.
- [STRONG AND SECURE POWER SUPPLY] This VNA is battery powered or USB powered. Built in 650mAh battery, could work for 2 hours continuously. For longer measurement time, kindly connect an external power source. The product interface displays battery usage, providing a clear understanding of the power status.
Options that change the buying decision
Option 001: 1 Hz resolution
Useful for fine frequency spacing and precise marker placement. It does not by itself improve amplitude accuracy, phase accuracy, noise floor or dynamic range.
Option 006: solid-state switching
Adds switching convenience for forward and reverse measurements and can support continuously updated four-S-parameter measurements in supported correction modes.
Option 010: time-domain analysis
Transforms frequency-domain data into response versus time or distance. Treat it as a legacy time-domain function, not as an equivalent to a modern TDR.
Option 011 and specialized configurations
Option 011 provides direct receiver access for specialized architectures. Listings may also mention high-power, mixer, sampler or high-dynamic-range options such as C02, H03, H85, H87, H88 and H89. These are configuration examples, not standard equipment on every 8720C. Require photographs of option labels, test-set connectors and the rear panel; an option number alone does not prove that the hardware is present, functional or calibrated.
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Rank #2
- [1MHz-6GHz ULTRA-WIDE RANGE] Upgraded NanoVNA-F V3 covers 1MHz to 6GHz. Features S21 dynamic range up to 65dB and S11 up to 50dB for fast, high-precision RF measurements.
- [801 SCAN POINTS & RTC] Delivers high data resolution with 101-801 customizable scan points and 12 calibration storage slots. Built-in Real-Time Clock (RTC) for easy timestamping.
- [4.3" IPS TOUCH SCREEN] High-resolution 4.3-inch IPS TFT LCD touch display offers wide viewing angles and clear visibility under bright outdoor light. Intuitive touchscreen interface.
- [VERSATILE RF MEASUREMENTS] Measures S-parameters, VSWR, Log Mag, Phase, Smith Chart, Group Delay, Resistance, and Reactance. Ideal for filters, amplifiers, cables, and duplexers.
- [4500mAh BATTERY & DURABLE SHIELD] Rugged metal aluminum housing shields against EMI interference. Built-in 4500mAh battery charges fully in 3 hours via Type-C for long field work.
Manuals and documentation
Use the official Keysight support page first. It lists:
- 8719C, 8720C, 8722A/C Network Analyzer Operating Manual (October 1995).
- 8719C, 8720C Microwave Network Analyzer Service Manual (February 1996).
Operating manual
Use it for front-panel operation, measurement setup, calibration, markers, display formats, state storage and legacy printer, plotter and disk functions.
Service manual
Use it for self-tests, diagnostics, internal assemblies, adjustments, disassembly and power-supply troubleshooting. Service work can require calibrated RF standards, other test equipment and high-voltage safety procedures.
Third-party dealers sometimes mirror data sheets, quick-reference guides and option supplements. Treat those as copies and confirm critical details against Keysight documentation.
Rank #3
- Wide Frequency Range: GOOZEEZOO SV4401A high-performance handheld vector network analyzer features a full 50kHz–4.4GHz measurement bandwidth. It supports precise S11 and S21 parameter testing, with 50dB dynamic range for S11 and 75dB for S21. Perfect for testing MF/HF/VHF/UHF antennas including shortwave, WiFi, Bluetooth and GPS antennas, as well as various RF components like filters, amplifiers, attenuators, cables, power dividers, couplers and duplexers
- 7-Inch HD Display: Equipped with a 7-inch 1024*600 high-definition IPS capacitive touchscreen with high brightness for clear viewing even under outdoor sunlight. Adopts full-touch control combined with 4 physical shortcut buttons, supporting fast frequency adjustment, scale switching, trace control, marker editing and screenshot capture. It delivers smooth and efficient operation for daily RF debugging and professional measurement work
- Sturdy Structural Design: Comes with durable professional N-type RF connectors, matched with N-to-SMA adapters and SMA extension cables for universal device connection. The compact 190×130×30mm body with rear support stand meets both portable outdoor testing and desktop fixed use needs. Integrated all-metal shell provides excellent EMI shielding, effectively isolating external electromagnetic interference and ensuring stable and accurate measurement results
- Long Battery & Large Storage: Built-in upgraded 6700mAh large-capacity battery composed of dual 3350mAh cells, supporting up to 10 hours of continuous working time for long-duration field and outdoor testing. Equipped with USB Type-C port for fast charging, data transmission and firmware upgrade. Pre-installed 8GB TF storage card conveniently stores calibration data, SNP files, test screenshots and various measurement records for easy data sorting and analysis
- Multi-System Compatibility: Fully compatible with Windows, Linux and MacOS systems. Users can connect the analyzer to a computer via Type-C cable for serial port control, supporting custom start/end frequency setting, real-time data acquisition and marker adjustment. Adopts 2026 latest upgraded firmware (SV6301A_App_v0.7.1), supporting one-click firmware upgrade via virtual USB drive for continuous performance optimization
How to make a reliable measurement
- Inspect the unit: record model, serial number and options; check ports, display, keys, fans and storage functions.
- Warm it up: follow the operating manual’s warm-up guidance before calibration.
- Set the sweep: choose the S-parameter or display format, frequency span, points, IF bandwidth, power and averaging appropriate to the device.
- Connect suitable standards: use standards and cables matching the connector interface; inspect them first.
- Perform a two-port calibration: use SOLT or another supported method and establish the intended reference plane.
- Connect the device under test: avoid side-loading ports, minimize adapters and use correct torque.
- Verify: measure a known standard or through connection and investigate discontinuities, unstable traces or excessive ripple.
- Save state and data: preserve calibration, conditions and exported results together; legacy transfer methods may require extra hardware.
Calibration removes systematic errors at a defined reference plane. It cannot repair damaged ports or cables, worn standards, drifting hardware, excessive noise, a failing source or receiver, or a unit that has not been tested across its advertised band.
Used-buying checklist
Verify configuration
- Photographs of front and rear labels, including serial number and option codes.
- Connector type, center-pin alignment, thread condition and evidence of cross-threading or excessive torque.
- Firmware revision, latest calibration date, calibration provider and certificate for the exact serial number.
- Confirmation of options 001, 006, 010, 011 and any high-power or mixer hardware.
Demand meaningful test evidence
- Self-test results and evidence that a two-port calibration completes.
- Calibration certificate with scope and traceability.
- S-parameter plots from both ports, including measurements near 20 GHz.
- Photos of the display, menus, connectors, fans and rear panel.
- A return period long enough to test the analyzer yourself.
“Powers on” or “tested good” does not establish microwave accuracy. One marketplace listing describes an 8720C as “Tested Good,” but that statement alone does not prove calibrated 20 GHz performance: see the listing.
Display and storage checks
Verify that an original or replacement LCD is readable at all brightness levels, aligns with the controls and is serviceable. Test legacy disk, printer, controller or file-export functions if your workflow depends on them.
Calibration and total acquisition cost
Budget for more than the chassis:
- Calibration and possible repairs discovered during calibration.
- Shipping, insurance and import charges.
- Microwave test cables, adapters, calibration standards and a torque wrench.
- Verification standards and legacy data-transfer accessories.
- A reserve for displays, fans, batteries, storage devices or power supplies.
National Test Equipment displayed a calibration price signal of $876, but scope, region, shipping, adjustment and repair requirements can change the invoice: view the service page.
Rank #4
- [50kHz-3GHz WIDE MEASUREMENT RANGE] Upgraded NanoVNA-F V2 features an expanded frequency range up to 3GHz. Utilizing the harmonic expansion of the SI5351 clock chip, it delivers precise measurements with a 40dB dynamic range at 600M-1GHz (SWR < 1.02), making it perfect for HF, VHF, and UHF applications.
- [4.3-INCH IPS TOUCH SCREEN] Equipped with a high-resolution 4.3" IPS TFT LCD display. It offers a larger viewing angle and excellent visibility even in strong outdoor sunlight. Easily read S-parameters, SWR, phase maps, group delay, and Smith charts at a glance.
- [5000mAh BATTERY & POWER BANK FUNCTION] Built-in upgraded 5000mAh 3.7V large-capacity battery ensures extended standby time. With its 2A high-current fast charging and USB interface, this analyzer can even be used as an emergency power source to charge your iOS or Android phones.
- [PREMIUM ALUMINUM SHIELDING] Designed with a standard, rugged aluminum alloy housing. This solid construction perfectly protects the precision SMA connectors and significantly reduces external electromagnetic interference, ensuring maximum measurement accuracy.
- [FIRMWARE UPGRADE & EASY OPERATION] Supports virtual U-disk for hassle-free user program upgrades. Features a highly responsive power switch and supports both English and Chinese menus. Connect to PC software for advanced data analysis and seamless frequency expansion.
Used-market price signals
The following are asking prices observed in an August 2026 snapshot, not completed-sale averages:
| Listing type | Observed asking price | Stated condition or inclusions |
|---|---|---|
| Several eBay listings | Approximately $6,160–$7,250 | Varied; inspect each listing |
| eBay listing | Approximately $5,999 | Seller advertised replacement color LCD and two-year NIST calibration |
| Transcat | Approximately $8,999 | Used 50 MHz–20 GHz unit with calibration certificate and six-month warranty stated |
| Seller-refurbished listing | Approximately $17,990 | Options 001 and 010 stated |
Examples can be checked at eBay’s product page, the calibrated/refurbished listing, Transcat and Used-Line. Compare landed, calibrated cost rather than the headline price.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Common failure modes
Powers on but fails self-test
Possible causes include memory, power-supply, source, receiver or other aging internal assemblies. A normal boot screen is not proof of functionality.
Calibration will not complete
Check calibration-kit definition, connector gender, standards, cable condition, test ports and internal source or receiver health.
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Best Value
- UPGRADED NANOVNA ANALYZER: AURSINC NanoVNA-H4 Vector Network Analyzer by Hugen features the latest V4.4 firmware, a 9kHz–1.5GHz measurement range, and a 4.0-inch LCD touchscreen. The Antenna Analyzer provides outstanding performance for S-parameter testing, antenna resonance analysis and SWR evaluation with excellent vector network measurement capabilities. It is an efficient testing tool for electrical engineers, ham radio operators, antenna builders and radio DIY enthusiasts
- IMPROVED FREQUENCY ALGORITHM: The improved frequency algorithm of Nano VNA H4 can use the odd harmonic extension of si5351 to support the measurement frequency up to 1.5GHz. The 50K-300MHz frequency range of the si5351 direct output provides better than 70dB dynamic. The extended 300M-900MHz band provides better than 60dB of dynamics, and the 900M-1.5GHz band is better than 40dB of dynamics. Used it to check out new cable or antenna installations and to routinely adjust the RF tuner for optimum
- BUILT-IN MICRO-SD PORT & TDR FUNCTION: This antenna analyzer features a brand new panel and a new SD port for data storage, supporting up to 32GB memory cards (not included). Unlike older NanoVNA versions, it lets you customize the date and time for easier data recording. Added TDR functionality—widely used to quickly measure coaxial cable length and locate faults via impedance discontinuity calculations. The default firmware's main function is antenna performance measurement
- PC CONNECTION & ANDROID CONTROL: Using the PC software NanoVNASaver, the Nano VNA H4 antenna analyzer can connect to your device, extract data for display on a computer, and save it to Touchstone files. You can also export Touchstone (snp) files via the software for use in various radio design and simulation tools. With its TX/RX method, the analyzer measures complete S11 and S21 parameters. To obtain S12 and S22 parameters, you only need to manually rewire the transceiver ports
- WHAT'S INCLUDED: 1 x NanoVNA-H4 Host (built-in 1950mAh long-life battery), 1 x 4pcs SMA Male Calibration Kit (open/short/load + SMA female-to-female connector, for precise calibration), 2 x 6.3-inch (16cm) SMA Male-to-Male RG174 RF Cables, 1 x USB Type-C Data Cable, 1 x Type-C to Type-C Cable, 1 x Lanyard (with integrated stylus), 1 x Extra Stylus Pen, 1 x User Manual. It's a great antenna analyzer for your ham station—easy setup, no complex calibration
Works at low frequency but fails near 20 GHz
This is a critical warning. Require upper-band plots or calibration evidence; low-frequency operation can hide degraded tracking or dynamic range.
Intermittent display
Aging backlights, connectors and improvised display conversions can cause intermittent operation. Buy only with a meaningful return policy.
Legacy file transfer fails
Older disk, printer and controller workflows may not fit modern automation. Confirm the actual interface and software path before purchase.
When a 8720C still makes sense
Good fits
- Fixed laboratory benches and teaching conventional VNA concepts.
- Filters, cables, antennas and amplifiers within 50 MHz–20 GHz.
- Repair or reverse-engineering laboratories.
- Organizations that already own compatible cables, standards and expertise.
Poor fits
- Measurements below 50 MHz.
- Compact field work, wideband multiport or differential testing beyond the installed configuration.
- Modern USB/LAN/SCPI automation without legacy integration effort.
- Projects requiring predictable current support, parts, calibration turnaround or a new-product warranty.
Current alternatives
| Alternative | Why consider it | Trade-off |
|---|---|---|
| Keysight P5004B Streamline VNA | Current Keysight platform, 9 kHz–20 GHz coverage and modern workflows | New professional instrument; generally far more expensive than an uncalibrated used 8720C |
| Keysight E5080B ENA | Current ENA-class platform for production, R&D and automation | Requires vendor or distributor quotation; not a drop-in equivalent for every setup |
| Other used VNAs | Agilent/HP 8722C, 8719C, older PNA, Rohde & Schwarz or Anritsu models may offer different bands or prices | Compare ports, dynamic range, power, calibration ecosystem, interfaces and repair support |
Keysight identifies the P5004B and E5080B as related replacement choices on the 8720C product page.
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Buy a 8720C only when the seller can document the exact configuration, provide return protection and demonstrate calibration or credible S-parameter performance near 20 GHz. It can be a cost-effective fixed-bench VNA, but its obsolete status, aging hardware and legacy interfaces make downtime and repair risk part of the purchase. Choose a current VNA when automation, support, predictable calibration and lifecycle assurance matter more than the lowest acquisition price.
Quick Recap
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