Also known as: electromagnetic spectrum, EM spectrum
The electromagnetic spectrum is the full range of electromagnetic radiation ordered by frequency (or, equivalently, wavelength). It spans from low-frequency radio waves through microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays — all the same phenomenon vibrating at different rates.1
Overview
Every part of the spectrum is electromagnetic energy travelling at the speed of light; only the frequency (and thus wavelength) differs. Radio occupies the low-frequency end, conventionally about 3 kHz to 300 GHz, which is slow enough that electronics can generate and detect it directly.
Relevance to SDR
Software-defined radios operate within the radio portion of the spectrum. Where a signal sits in that range — its band — determines how it propagates, what antenna it needs, and what equipment can receive it.
Sources
-
Electromagnetic spectrum — Wikipedia, overview of the full range of electromagnetic radiation. ↩