Oscilloscope vs Spectrum Analyzer: Do I need a Spectrum Analyzer or an Oscilloscope?

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Oscilloscopes and spectrum analyzers are two very important instruments while signal analyzing. However, oscilloscope vs spectrum analyzer has been a common topic since the beginning of their invention. So, I have decided to share my experience and a little bit of research from the internet to help you get an answer to the question.

To know whether you need a Spectrum Analyzer or an Oscilloscope, at first, you will have to know what these really are.

What is an Oscilloscope?

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An Oscilloscope is a testing device that displays the voltage change over a certain time as a two-dimensional graphics (Voltage on the vertical axis and time on the horizontal axis). It allows you to analyze the displayed waveform in terms of frequency, rise time, amplitude, and many more.

With an Oscilloscope, it’s quite easier to understand whether the signals of your circuits are working properly or not. Also, you can identify noises’ locations on your circuits and can fix them easily.

What is a spectrum analyzer?

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A spectrum analyzer is used for measuring an input signal’s magnitude against frequency. It works extensively in the full frequency series of the device. This analyzer mainly measures the power of known as well as unknown signals’ spectrum.

Generally, spectrum analyzers are used for electrical input signals. However, you can also find it for other signals and compositions such as optical light waves or acoustic pressure waves.

Oscilloscope vs spectrum analyzer:

Oscilloscope vs Spectrum Analyzer

While they might seem quite similar to each other, in reality, they have a lot of differences that create the question about which one you would need.

Generally, you use an Oscilloscope when you need more detailed timing information of a signal or the connections between various signals. You can also use it to find out the relative time delay between two or more signals. Whereas, you use a spectrum analyzer to identify the frequency properties of a signal or wave.

These are the most common differences between these two devices. You can judge them based on some other properties too.

Real-time bandwidth: 

Real-time bandwidth can be an important factor when you are trying to find out which one you should use. To be clear, real-time bandwidth is mainly used to analyze a signal in real-time.

In the case of Oscilloscopes, the measurement frequency range is usually the bandwidth. However, the real-time bandwidth decreases whenever the vertical scale is one the most sensitive point. So, we can say that the real-time bandwidth of the Oscilloscopes changes according to the vertical scale setting.

You can define the spectrum analyzer bandwidth with a resolution or IF bandwidth. In this case, the final analog’s IF can be used as the real-time bandwidth.

An Oscilloscope has an effective analog real-time bandwidth that can range from hundreds of megahertz to several gigahertz. On the other hand, most spectrum analyzer has a bandwidth range from ten megahertz to highest 500 megahertz.

So, if you consider all the features, oscilloscopes are better than the spectrum analyzers in the case of real-time bandwidth. Especially, if you are working with some ultra-wideband signal analysis, oscilloscopes are your best choice.

Time Domain and Frequency domain:

Earlier, the oscilloscopes were only known for controlling the time domain whereas the spectrum analyzer was for showing the electromagnetic signals in the frequency domain. However, you can now use both of them for frequency as well as time domain. But they still have power in a different sector individually.

In this case, the oscilloscope will provide you with a user-friendly and flexible operation and the spectrum analyzer will ensure a great bandwidth. So, since both of them are better in their own fields, you will have to choose one according to the work or lab project you will use it for.

Dynamic Range: 

The dynamic range is measured by the difference between the minimum and the maximum signal. Now, an oscilloscope and a spectrum analyzer can provide two different results while measuring the largest and smallest signals at the same time.

Firstly, oscilloscopes are confined to the AD sampling bits’ number as well as the noise floor. Usually, these instruments have a dynamic range of a maximum 50dB. On the other hand, spectrum analyzers don’t consider the near-end noise or phase noises while their dynamic range is limited to the average noise level along with second and third-order distortion. You can get a dynamic range of 90 dB from these.

If you compare the two devices based on the dynamic range. Surely, spectrum analyzers win.

Power Measurement: 

Since it’s one of the most important factors of a domain frequency analysis, Oscilloscopes and spectrum analyzers have a different amount of influence on the power measurement accuracy.

You can easily find the difference among them by comparing the power amount of a 1GHz frequency signal. However, you can also find that the oscilloscope and spectrum analyzer have a power measurement difference of only 0.2dB which makes your task to choose one of the more difficult.

But to make this easier for you, I can tell that the spectrum analyzer’s power measurement accuracy is better than the oscilloscope.


What is FFT on an oscilloscope? 

Ans: The FFT on an oscilloscope can be referred to as an analysis device that displays the measured time-domain (amplitude vs. time) based on the frequency domain (amplitude and phase vs. frequency) while being an algorithm that helps to lessen the calculation time of the DFT. Also, you can add a spectrum analysis to a digital oscilloscope using the FFT.

How much is an oscilloscope?

 Ans: That depends highly on the frequency and bandwidth you are looking for to buy. While you can buy an oscilloscope with a 200 – 100MHz bandwidth with a few hundred dollars, the ones with bandwidth over 1 GHz might cost you up to $20,000 – $30,000!

What is a good beginner oscilloscope?

Ans: Experts recommend using Rigol DS1052E, the Hantek (DSO5072P), or the Siglent Technology SDS1104X-E as beginners. They are of high quality and comes in a good price range.


Since the article is about an oscilloscope vs spectrum analyzer, you are most probably waiting for me to declare which one is the best. But the truth is both of them are very good in their own fields.

While oscilloscopes will provide you with better Real-time bandwidth, spectrum analyzers are best in terms of technical indicators. So, you should choose one of them according to the test requirements that you are taking on.

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