The signals are displayed first in a pattern then the spectrum analyzer plots the amplitudes on the vertical axis and the frequencies on the horizontal axis. The vertical axis represents the strength of the signal while the horizontal axis represents the time based frequencies.
The spectrum analyzer is different from an oscilloscope, another device that measures signals. One of the basic differences is that a spectrum analyzer shows the received signal strength against the frequency while an oscilloscope displays received signal strength against time. This makes the spectrum analyzer useful for measuring and studying the amplitude response of a device against a frequency. Measurement output of spectrums is in decibels or dbm while in oscilloscopes, the measurement output is in volts.
Moreover, an oscilloscope is unable to measure very low voltage levels and for that matter it is used mainly for low frequencies and high amplitude measurements only. But in the case of spectrum analyzers, the device can measure as low as -120 dBm in amplitude and as high as 150GHz in frequencies. Because of the things that spectrum analyzers can do, the device components are usually more complex than that of an oscilloscope making the former a little more expensive that the latter.
The spectrum analyzer has a number of uses. The machine can be used to conduct device frequency response measurements which basically mean measuring the amplitude response of a device against its frequency. You can also conduct microwave tower monitoring with the spectrum analyzer. By using the analyzer, you will be able to measure the transmission and receiver strength of a tower. With the analyzer, you could also do interference measurements allowing you to verify and identify interferences in large RF installations. A spectrum analyzer can also do return-loss measurement, spurious signals measurement, inter-modulation measurements, satellite antenna alignment and harmonic measurements.
Some of the basic features of a spectrum analyzer include color displays; continuous 30 Hz to 26.5 GHz sweep or more depending on the machine; precision time base and 1 Hz counter resolution; fast digital resolution bandwidths, adjacent channel power, channel power, carrier power, occupied bandwidth percentage and time-gated measurements standard; settings that can conduct digital radio and phase noise measurements; and an easily transfer screen image or trace data.