Spectrum Analyzer VBW: What Does It Mean? - OneSDR

A spectrum analyzer is a necessary tool for measuring and visualizing frequency signals.

One of its key settings is VBW (Video Bandwidth). Understanding VBW is essential for achieving accurate and clear signal measurements, especially when working with weak signals or fluctuating noise levels.

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In this article, we’ll explain what VBW (Video Bandwidth) means in a spectrum analyzer, how it affects signal display, and how to set it correctly for different applications.

Table of Contents

What Is VBW (Video Bandwidth) in a Spectrum Analyzer?

Video Bandwidth (VBW) controls the smoothing of the displayed signal on a spectrum analyzer. It applies a low-pass filter to the measured signal after the Resolution Bandwidth (RBW) stage, reducing noise and making the signal easier to interpret.

VBW in Simple Terms

Lower VBW = Smoother signal display, but slower updates.
Higher VBW = Faster signal response, but more noise visible.

How Does VBW Affect Spectrum Analysis?

Signal Smoothing & Noise Reduction

A low VBW reduces display fluctuations, helping identify weak signals in a noisy environment.
A high VBW maintains a fast response but may make the signal appear noisier.

Measurement Stability

Lower VBW provides a clearer, more stable signal display.
Higher VBW updates the display faster, making it useful for capturing fast-changing signals.

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Relationship Between VBW and RBW

VBW is always equal to or lower than RBW.
A VBW of 1/10th RBW is commonly used for an optimal balance between speed and noise reduction.

Choosing the Right VBW for Your Application

Application	Recommended VBW	Why?
Fast signal detection	VBW = RBW	Faster response time
Noise reduction & weak signals	VBW = 1/10th RBW	Smooths signal display
Highly stable measurements	VBW = 1/100th RBW	Minimizes fluctuations

Final Thoughts

VBW plays a key role in spectrum analysis, helping balance speed, noise reduction, and signal stability.

Setting VBW too high can result in a noisy display, while too low can cause slow updates. By adjusting VBW correctly relative to RBW, you can enhance measurement accuracy and improve signal clarity in various applications.