Used Equipment Store

Account Benefits

Get a customised view of the Used Equipment Store

Manage your details to get quick responses by the team

Stay up-to-date on specials, price and availability

Already have an account? Log In

Create Your Account

Sign up to receive marketing or promotional emails from Keysight

For professional and industrial use only
By clicking the Get Updates button, you agree to Keysight’s Privacy Policy.
Your browser limits use of the Used Keysight Equipment website.
Please consider switching to a current version of Chrome, Firefox, Edge or IE11 to use this site.

As an engineer, are you tired of struggling to pinpoint the source of signal interference or distortion? Whether in a radio transmission or a power line, these problems can wreak havoc on your equipment and cause costly downtime.

The problem is that many methods of troubleshooting are time-consuming and ineffective. But there is a solution! By learning how to use and read a spectrum analyzer, you can quickly and easily identify the source of the problem and get your equipment back up and running in no time.

This article will show you how to read a spectrum analyzer to diagnose and solve any interference or distortion problems. We will cover the basics of 

  • Spectral analysis
  • The types of spectrum displays
  • What each part of the display means

Armed with this knowledge, you'll be able to read a spectrum analyzer like a pro in no time!

Display Elements of a Spectrum Analyzer

To correctly read a spectrum analyzer, it's vital to understand all of the separate elements of the display entirely. Each element provides essential information to troubleshoot and solve signal issues.

The main display elements of a spectrum analyzer include the horizontal axis, vertical axis, scale, center frequency, and span. Here is a summary of those display elements. 

Display ElementMeaning
Horizontal axisThe horizontal axis of the analyzer shows the frequency band on a logarithmic scale, ranging from low to high.
Vertical axisThe vertical axis displays amplitude or signal strength.
ScaleThe scale determines the display's range of frequencies and amplitudes shown on the readout. It usually consists of lines that represent different voltage levels at regular intervals.
Center frequency The center frequency is the frequency at the middle of the screen.
SpanThe span is the range of frequencies displayed on the spectrum analyzer – it can vary depending on how much you want to see.

Understanding each display element will allow you to quickly identify and solve signal issues. Let's take a closer look at each element and how they work together.

Signal Analyzers

Rugged Precision, Anytime

See N9020 Special Offers

Horizontal Axis

The horizontal axis of the spectrum analyzer display represents the measured range of frequencies, with the frequency unit (such as MHz or GHz) and the range of frequencies displayed (such as 100 MHz to 1 GHz and higher). The frequency axis determines the location of the signal on display and identifies any frequency-related issues.

Frequency measures how often a wave oscillates, measured in hertz (Hz). For example, a signal wave with a frequency of 1 Hz oscillates once per second. A wave with a frequency of 2 Hz oscillates twice per second, and so on. 

The frequency measures how "fast" the wave oscillates and how "tight" the wave's oscillations are. A wave with a higher frequency oscillates more rapidly and the oscillations are closer together than a wave with a lower frequency.

The frequency of a signal can tell you a lot about the source of the signal and identifies different types of signals. For example, a low-frequency signal (such as a power line) will have a lower frequency than a high-frequency signal (such as a radio transmission).

The frequency axis also allows the user to zoom in and out of the display to focus on a specific range of frequencies. This feature can be helpful when identifying a particular signal or isolating a specific frequency range.

By understanding the frequency axis of the spectrum analyzer display, you will be able to quickly identify the location of the signal and any frequency spectrum issues that may be causing signal interference or distortion.

Vertical Axis

The spectrum analyzer's vertical axis represents the signal level, also known as the amplitude. You label it with the amplitude unit (such as dBm, dBV, or dBmV) and the range of amplitudes displayed (such as -80 dBm to 0 dBm). The amplitude determines the strength of the signal on display and identifies any amplitude-related issues.

The amplitude of a signal helps to identify different types of signals. For example, a low-amplitude signal will have a lower power level than a high-amplitude signal. The amplitude axis allows the user to adjust the display's gain to see weaker signals better.

By understanding the amplitude axis of the spectrum analyzer display, you will be able to quickly identify the strength of the signal and any amplitude-related issues. Understanding amplitude and its representation on the vertical axis is crucial to setting reference levels and precise measurements, especially when measuring very weak or very strong signals.

Scale

The scale of the spectrum analyzer display represents the amplitude and frequency of the analyzed signal. The scale is typically divided into equal intervals and labeled with the corresponding amplitude or frequency values.

You can adjust the scale to display the signal in different ways, such as linear or logarithmic.

  • In a linear scale, the values on the vertical axis are equally spaced, meaning that the difference between the two scale divisions on the axis is the same at all points. The linear scale is less commonly used in spectrum analyzers because the dynamic range of signals can be very large, and the weaker signals can be challenging to see or hidden in the noise floor. But it can be helpful for certain types of measurements or situations where the range of amplitudes is not very wide, and the goal is to read and understand the measurements with high precision and accuracy.
  • A logarithmic scale, also known as a log scale, displays signals in a logarithmic way, meaning that the amplitude or frequency is represented in a logarithmic relationship to the signal strength. Logarithms are mathematical functions that allow you to compress a wide range of values into a smaller range, allowing a more practical representation over a large range of signal values.

The logarithmic scale is most commonly used in spectrum analyzers and allows the user to view a wide range of amplitudes, making it easier to identify weaker signals.

The scale is usually calibrated to a specific band of frequencies and amplitudes, depending on the device and the application. For example, a spectrum analyzer designed to test RF devices is calibrated to a range of frequencies from a few MHz to several GHz and amplitudes from -80 dBm to 0 dBm.

It's important to understand the scale and how it's calibrated, as it directly affects the accuracy and resolution of the measurements and the ability to identify signals. Understanding the scale will also allow you to interpret the results of your measurements correctly.

Centre Frequency

The center frequency of the spectrum analyzer display is the reference point for the frequency axis. The location of the centre frequency is in the middle of the displayed frequency range. It is usually labeled with the corresponding frequency value represented as a vertical line on the display.

The center frequency is a user-defined value that you adjust depending on the measurement task. It is a reference point to help the user orient themselves on the frequency axis and identify the signal's location on display. The user can adjust the center frequency to change the displayed frequencies and zoom in or out of specific frequency ranges.

When you adjust the center frequency, the other frequencies on display will shift accordingly, with the new center frequency becoming the new reference point.

Understanding the center frequency is essential, as it directly affects the displayed frequency range and the ability to identify and isolate specific signals. It also allows you to correctly orient yourself on the frequency axis and make precise measurements.

Span

The span of the spectrum analyzer display is the range of frequencies displayed on the frequency axis. It is labeled with the corresponding frequency range, such as 100 MHz to 1 GHz, and represents the distance between the start and end frequencies on the frequency axis.

You can adjust the span to change the range of displayed frequencies. When you increase the span, a wider range of frequencies is displayed on the frequency axis, allowing the user to see a larger portion of the spectrum. When the span decreases, a smaller range of frequencies is displayed on the frequency axis, allowing the user to zoom in and see a more detailed view of a specific frequency range.

When you adjust the span, you will also need to change the center frequency to ensure that the signal of interest stays centered on the display. This feature is useful when isolating a specific frequency range or identifying a particular signal.

Unlock the Power of Precision With Keysights Accurate and User-Friendly Spectrum Analyzers

At Keysight, we provide the industry's best spectrum analyzers to help you make accurate and reliable measurements. With our intuitive and easy-to-use user interfaces and cutting-edge technologies, you can get fast, actionable insights to take your testing to the next level.

Do you want to avoid missing project deadlines due to long delivery times? As an engineer, you know that timely delivery is crucial for meeting project milestones and keeping your customers happy. That's why you need a supplier who can deliver the equipment you need when you need it.

We understand the importance of fast delivery times and work hard to ensure that our customers receive the equipment they need as quickly as possible. For US customers, we offer a fast two-week delivery time for selected spectrum analyzers, which is 6-19 weeks faster than other resellers!

If you are looking for a spectrum analyzer that can measure a wide range of signals with precision and reliability, a Keysight premium refurbished spectrum analyzer is a perfect choice.

Spectrum Analyzer Functions

A spectrum analyzer is a measurement tool used to visualize and analyze the spectral content of signals. It accomplishes this by measuring the magnitude of the input signal versus its frequency over the entire frequency span. 

Think of this as a means to see a signal's "frequency fingerprint." This fingerprint will help you determine the signal power of electronic devices and how that signal makes up different frequency components.

Its main test functions identify

  1. Frequency
  2. Power
  3. Bandwidth
  4. Amplitude
  5. Phase and other parameters of a signal

A spectrum analyzer also has many applications. You can use a spectrum analyzer for radio, wireless communication, and audio signal engineering. They will also help troubleshoot and optimize electronic wireless networking equipment.

Making Adjustments

When using a spectrum analyzer, it is vital to understand how different settings and features affect the displayed results. Adjusting various settings allows you to optimize the instrument's performance and make more accurate measurements.

Three key settings to know are

  1. Gain. The gain controls the instrument's sensitivity and determines the signal's amount of applied amplification. Increasing the gain can make weak signals more visible on display. However, if the gain is set too high, it can lead to distortion or saturation of the signal. It's important to set the gain correctly to get a clear and accurate signal reading.
  2. Scan rate. The scan rate controls the speed at which the instrument scans the frequency spectrum. A higher scan rate will provide a faster display update, but it can also lead to a lower resolution and accuracy of the measurements. A lower scan rate will provide a higher resolution and accuracy, but it will also slow down the update of the display. Selecting the appropriate scan rate depending on the particular signal measurement is important.
  3. Attenuation. Attenuation reduces the amplitude of the signal before the gain amplifies it. Reducing the amplitude of the signal can prevent distortion and saturation. It's important to set the attenuation correctly to get a clear and accurate signal reading, especially when working with high-power signals.

How To Read the Results

Reading the results of a spectrum analyzer can seem daunting at first. Although, it becomes relatively straightforward with a clear understanding of the display elements and the instrument's functions. Here is a step-by-step guide on how to correctly read a spectrum analyzer.

Oscilloscopes

Solve Signal Issues Before They Escalate

See MXR608A Special Offers

Step 1: Familiarize Yourself With the Display Elements

Before making any measurements, it's important to familiarize yourself with the different elements of the display. These include the frequency axis, amplitude axis, center frequency, span, and any markers or traces that may be present. Make sure you understand what each element represents.

Step 2: Connect the Signal

Connect the signal you want to measure to the spectrum analyzer's input. Ensure that the signal is within the instrument's frequency range and the signal level is within the instrument's dynamic range.

Step 3: Adjust the Settings

Once you connect the signal, adjust the settings, such as the gain, attenuation, and scan rate, to optimize the display for your measurement. Set the gain correctly to get a clear and accurate signal reading.

Step 4: Observe the Display

Observe the display and note the signal's frequency and amplitude. Look for any peaks or dips and any unwanted frequency components. Use the markers or trace function to measure the specific frequency and amplitude of the signal.

Step 5: Interpret the Results

Interpret the measurement results by comparing them to the expected results or signal specifications. Identify any issues or deviations from the expected results and troubleshoot accordingly.

Now you know how to read the results, here are a few possible displays to help illustrate the steps outlined above. 
 

ScenarioExplanation
A single-frequency signalThe display shows a single-frequency signal with a clear peak at the expected frequency. The amplitude of the signal is within the predicted range. The center frequency is set to the desired frequency. Everything looks as expected.
Interference signalThe display shows multiple frequency peaks, indicating the presence of interference. This is due to the signal being close to other signals. The amplitude of the interference signals is higher than the desired signal, indicating that you need to adjust the gain. Adjusting the gain will reduce the amplitude of the interference signals and improve the accuracy of the measurement.
Distorted signalThe display shows a signal with a distorted shape, indicating that the signal is experiencing distortion. A high gain setting or incorrect attenuation could cause this, masking lower-level signals. The amplitude of the signal is lower than expected. Take steps to reduce distortion, such as reducing the gain or increasing the attenuation.

These are a few examples of how to read a spectrum analyzer with different display results. With practice and experience, you will be able to quickly and accurately interpret the results of your measurements. Now that you understand the basics of how to read a spectrum analyzer, get out there and start making measurements!

Unlock the Secrets of Your Signal With a Keysight Spectrum Analyzer

Understanding how to read a modern spectrum analyzer is the first step in unlocking the secrets of your signal. With Keysight's wide range of spectrum analyzers, you can confidently make precise and accurate signal measurements.

If you are looking for a quality spectrum analyzer, look no further than Keysight. Our premium refurbished analyzers are the best on the market, available at a fraction of the price. We guarantee you will not have to compromise on performance and accuracy when buying from us.

Closing Thoughts From Keysight

In this article, we have discussed the various methods of how to read a digital spectrum analyzer. We have gone through connecting a signal, adjusting the optimum settings, and observing the display. We have also discussed different display examples and how to interpret them accurately.

Although it can seem intimidating at first, with practice and experience, you will be able to quickly and accurately interpret the results of your measurements. Whether you are new to spectrum analysis or experienced, Keysight has the right equipment solution. Our wide range of refurbished analyzers are reliable, accurate, and easy to use so that you can make the most out of your measurements.

Whenever You’re Ready, Here Are 4 Ways We Can Help You

Browse our premium used spectrum analyzer offers

  1. Call tech support US: 1 800 829-4444
    Press #, then 2. Hours: 7 am – 5 pm MT, Mon– Fri
  2. Talk to our sales support team by clicking the icon (bottom right corner) on every offer page
  3. Talk to your account manager about your specific needs

ENA Vector Network Analyzers

Perfect Signals, Perfect Performance

See E5080B Special Offers