WHY VNA 2.0.33

WHY VNA is a Windows measurement and analysis application for LiteVNA and compatible NanoVNA V2 instruments.

The program started as a simple PC interface for a VNA, but has gradually developed into a complete RF measurement environment. 

The aim is not only to display S-parameters, but to make inexpensive VNA hardware useful as a practical measurement workstation for amateur radio, development and laboratory work.

The user interface and measurement workflow are inspired by conventional professional network analysers, while adding analysis, documentation and automation functions that are convenient on a PC.

WHY VNA is supplied as a standalone Windows application and normally requires no installation.

I have spent many hours on the software’s available on my site. But it is in 2026 they are more useable to others. Now I use AI to wash my old code, that’s why the speed of updating is heavily improved.

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Main features

WHY VNA includes measurement and analysis functions for antennas, filters, transmission lines, components, resonators and active RF devices.

VNA measurements

• S11, S21, S12 and S22
• Magnitude and phase
• Return loss and SWR
• Complex impedance
• Group delay
• Smith chart
• Admittance Smith chart
• Polar display
• Four independent markers
• Marker search, tracking and delta measurements
• Continuous and segmented sweeps
• Full two-port measurement workflow

Calibration and fixture correction

• SOLT calibration
• Reusable calibration profiles
• Calibration-kit definitions
• Port extension
• Time-domain gating
• Fixture de-embedding
• Symmetric 2×-Thru fixture characterization
• Fixture quality and usable-frequency guidance

WHY VNA can characterize a measured symmetric 2×-Thru fixture and extract electrical left and right fixture halves.

Version 2.0.16 also evaluates the measured fixture and reports a recommended de-embedding frequency range together with an approximate extension range.

This helps prevent a fixture model from being used far beyond the frequency range where it remains physically meaningful.

Antenna and filter analysis

• Antenna resonance analysis
• SWR and return-loss analysis
• Filter bandwidth
• Insertion loss
• Rejection
• Group delay
• Resonator analysis
• Limit testing

Component and crystal analysis

Components can be measured using:

• one-port reflection
• two-port series-through
• two-port shunt-through

WHY VNA can extract complex impedance and investigate the frequency-dependent behaviour of real resistors, capacitors and inductors.

Crystal and resonator analysis is also included.

Component-analysis results can be exported directly to CSV for further processing or documentation.

TDR and cable measurements

Frequency-domain measurements can be transformed into the time and distance domains.

Applications include:

• cable length measurement
• distance-to-fault
• locating impedance discontinuities
• connector inspection
• transmission-line analysis
• multiple-reflection analysis

LNA and amplifier characterization

WHY VNA includes a dedicated LNA / Amplifier Characterization mode.

It can determine:

• gain versus frequency
• peak gain
• input return loss
• input SWR
• −3 dB bandwidth
• gain flatness
• group delay
• relative gain compression
• 0.5 dB compression
• 1.0 dB compression

With complete two-port data, additional amplifier characteristics such as output match, reverse isolation and stability can also be investigated.

High-gain amplifiers can overload the VNA transmission receiver even when source attenuation is used.

WHY VNA therefore includes receiver-overload detection and support for an external output protection attenuator.

For best accuracy, the protection pad can be included in the THRU calibration so that its loss is removed from the displayed amplifier gain while the Port 2 receiver remains protected.

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Relative gain compression

WHY VNA can progressively reduce the LiteVNA source attenuation and observe how amplifier gain changes as RF drive increases.

This allows the transition from the small-signal region into gain compression to be investigated.

The measurement is deliberately reported as relative source drive unless absolute Port 1 power has been independently calibrated.

WHY VNA therefore does not present relative compression as an unsupported absolute P1dB value.

Absolute input P1dB requires calibrated RF source power.

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Fixture de-embedding

At higher frequencies the measurement fixture itself can become a significant part of the measured result.

PCB traces, connectors, adapters, component pads and transitions all contribute electrical length, loss and mismatch.

WHY VNA can remove these effects from a full two-port measurement using S2P fixture models.

A symmetric 2×-Thru fixture can also be measured directly and separated into two electrical fixture halves.

The resulting models move the effective reference planes from the VNA connectors toward the DUT itself.

This is particularly useful for:

• PCB-mounted components
• filters
• amplifiers
• matching networks
• microwave devices
• component test fixtures

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Practical measurement validation

WHY VNA has been compared with independent RF laboratory equipment during development.

One validation used a KU LNA 144A measured with:

• WHY VNA / LiteVNA67
• Eaton 2075 Noise Figure Analyzer
• Giga-tronics 8541 power measurement system

The three independent gain measurements agreed closely around the 144 MHz passband.

A second validation used a purpose-built Rogers 2×-Thru fixture and a 51-ohm reference resistor.

Without fixture correction, the measured component impedance became increasingly distorted as frequency increased.

After 2×-Thru de-embedding, the extracted DUT impedance remained very close to the expected 51 ohms through the lower microwave region.

These measurements also demonstrate an important principle:

Software cannot remove the physical limitations of the VNA, calibration standards or test fixture. Correct measurement technique remains essential.

A separate Practical Measurement Validation PDF is included with the WHY VNA download.

It contains the complete measurements, graphs, screenshots, comparison data and the full 1001-point fixture measurement datasets for readers who want to examine the validation in detail.

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Measurement integrity

An important design principle in WHY VNA is that calculated results should be based on information the connected hardware can actually measure.

WHY VNA therefore does not attempt to manufacture values from insufficient data.

For example:

Noise figure requires a suitable noise-measurement system and calibrated noise source.

Absolute P1dB requires calibrated absolute RF source power.

IIP3 and OIP3 require a calibrated two-tone measurement.

WHY VNA can perform relative compression analysis because changes in source attenuation are known, but the result is clearly identified as relative.

This distinction is particularly important when inexpensive measurement hardware is used for serious RF measurements.

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Measurement and analysis tools

WHY VNA also includes PC-based tools intended to make repeated measurements and comparison easier.

These include:

Sweep History – compare measurements over time.

Waterfall – visualize changes over repeated sweeps.

Live Measurement Lab – continuously monitor selected measurement parameters.

Trace Memory – store and compare traces.

Trace Mathematics – mathematically compare measurement data.

Limit Testing – evaluate measurements against defined limits.

Reports and export – save measurements for analysis and documentation.

Touchstone, CSV, PNG, PDF and HTML export functions are available where appropriate.

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Supported instruments

WHY VNA is primarily developed for:

• LiteVNA64
• LiteVNA67
• compatible NanoVNA V2 instruments

Experimental support for NanoVNA-F V2 is also included.

Some functions depend on the capabilities of the connected hardware and firmware.

Extended frequency operation beyond the normal specified range of a VNA should always be regarded as experimental and verified against suitable reference equipment.

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Calibration

Accurate VNA measurements depend heavily on calibration.

WHY VNA supports SOLT calibration together with reusable calibration profiles and calibration-kit definitions.

Real OPEN and SHORT standards are not electrically perfect, particularly at microwave frequencies.

Calibration-kit models allow their delay, loss, capacitance and inductance characteristics to be included instead of treating the standards as ideal components.

Calibration state and applicable frequency range are shown in the program to help prevent accidental use of unsuitable calibration data.

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A low-cost VNA is still a measurement instrument

WHY VNA can considerably extend what can conveniently be done with LiteVNA and NanoVNA-class hardware.

However, software cannot overcome the fundamental limitations of the RF hardware.

Measurement accuracy is still affected by:

• dynamic range
• receiver headroom
• source power accuracy
• directivity
• isolation
• connector quality
• fixture quality
• calibration standards
• calibration technique

The practical validation measurements included with WHY VNA demonstrate both the capabilities and the limitations of the measurement system.

Understanding the measurement setup is just as important as reading the value displayed on the screen.

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Safety and measurement limits

Never exceed the permitted RF power or DC voltage at the VNA ports.

Particular care should be taken when measuring:

• powered amplifiers
• transmitters
• active devices
• bias networks
• unknown circuits
• equipment that may contain DC voltage

Use suitable DC blocks, attenuators and protection components where required.

Critical measurements should always be verified using appropriate standards and reference equipment.

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Download WHY VNA 2.0.33

Windows standalone application.

The download package includes:

• WHY VNA
• complete illustrated user and measurement manual
• Practical Measurement Validation PDF

why-vna-2-0-33.zip

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About the project

WHY VNA is developed primarily for my own amateur-radio and RF measurement work.

It has grown considerably as new measurement problems have appeared and as the capabilities of inexpensive VNA hardware have improved.

The project is intended as a practical engineering tool rather than a replacement for professional laboratory instrumentation.

However, the practical validation measurements show that with careful calibration, suitable fixtures and a correct measurement setup, surprisingly useful results can be obtained from inexpensive VNA hardware.