Why Do We Use Scans from Spectrum Analyzers and How Do We Interpret Them?

RF problems can be tricky to diagnose because you can't see what is causing them - unless you have a Spectrum Analyzer. Spectrum Analyzers, such as the RF Explorer Pro and Spectrum Recorder, provide you with RF scans that visually represent the RF spectrum conditions in your location. This is displayed as a graph, either in real time or at an instant in time, that shows the signal's amplitude versus frequency. The amplitude is measured in decibels, and the frequency is in hertz. With these measurements, you can identify any out-of-band signals or noise that may be present. This allows you to isolate and work around or remove noise and spurious signals, ensuring better microphone and IEM performance. It also allows you to obtain accurate measurements, which we will discuss later.

The biggest neighbor to our wireless mics and IEM’s is broadcast television transmissions.  We need scans to help us operate our mics and IEMS and tune them to the most open spots in the TV Band spectrum. The first step to making Wireless Mics and IEMs work at their best to tune them to areas where there is no TV channel.  

Our Mics and IEMs are also near the space that is reserved for the 5G Cell network and can be indirectly affected by it.  This can be more popular than traditional Broadcast Television in our populated areas where there is good internet.  This energy can leak over to our microphones and IEMs and we need RF Scans to see it. 

In addition, our Mics and IEMs can be affected by other RF energy in the rooms we use them. This includes LED walls, Power Distros and many cell phones used together. The noise floor (the sum of all non-intentional RF signals, like TV channels, cell phones, and video walls) has to be low and your wireless device signal needs to be high.   This is the signal to noise ratio and this needs to be at its best.  

Another reason that we need spectrum analyzer scans is to see the problems of poor frequency coordination relating to the wireless devices we use in a given area.  Poor frequency coordination (mathematically incorrect chosen frequency deployment) and the combination of using transmitters in close proximity will cause problems within your own system.  This is called intermodulation distortion and we need Spectrum Analyzer scans to see this.  

We can get scans measuring RF with an antenna on the Spectrum Analyzer directly or by connecting the output of an RF device or system directly to it. A trace (or a snapshot of your RF scan) is then imported into a coordination program like Wireless System Builder to compare the energy recorded along with a graphic representation of DTV in the area.  The DTV information comes from a database on the internet and it is imperative to compare your scan with the database information because the database could be missing information or out of date.

Overall, when we avoid active TV channels and other sources of interference, we are creating the best signal to noise environment for our wireless systems.  This gives us better range with no noises and dropouts.

The other benefits of using a spectrum analyzer is that we can see if our own equipment is causing noise.  We can see intermodulation distortion, and test cables, antennas and filters for accuracy.  

Techs will often zoom in and out on the scan to make sure that they are seeing everything

Techs will often zoom in and out on the scan to make sure that they are seeing everything

Techs will often zoom in and out on the scan to make sure that they are seeing everything

How To Use a Spectrum Analyzer

The controls and interface of a spectrum analyzer can vary depending on the model and manufacturer, but most spectrum analyzers have several standard features.

• You control the frequency span, range, and resolution by dials or buttons on the front panel. Adjusting these settings alters the range of frequencies displayed on the screen.
• The trace, or line, on the screen represents the strength of the signal frequency. You adjust the amplitude of the trace by using the vertical scale knob. Move the trace up and down on the screen by adjusting the offset.
• The level setting controls the maximum and minimum power levels displayed on the screen, known as the vertical scale. It is important to note that the level setting does not affect the actual power of the measured signal. You adjust the level setting by using the dial on the front panel.
• The time base, or sweep speed, is another important spectrum analyzer feature. This controls how long it takes for the trace to move across the screen. A faster sweep speed will allow you to see brief signal anomalies. Adjust the time base to suit your desired speed by using a dial on the analyzer's front panel. Most spectrum analyzers have an auto-scale feature that automatically adjusts the level and sweep speed settings. This is a convenient feature if you are unsure what settings to use.

It is very important to have a RF Spectrum Analyzer on site for any set up.  One microphone is just as important as many used together and ultimately the Spectrum Analyzer and a Frequency Coordination program should be used together to get best results.  

Want to talk about spectrum analyzers or scans with a member of our team?  Reach out now.