The horizontal axis shows frequency (in Hz, MHz, or GHz), and the vertical axis shows amplitude, which is the power or strength of each signal (typically in dBm). Once you understand these two axes and a handful of key controls, you can interpret nearly any measurement the. A spectrum analyzer measures how signal power varies with frequency. You can see exactly which frequencies are in a signal and how strong they are. From detecting hidden sources of noise to verifying device performance against industry standards, this instrument is one of the most versatile tools in an engineer's lab. Most spectrum analyzers automate.