The physics of radio bands and channels

May 2, 2006
This technical article looks at the principles of radio technology to explain the differences in performance between different radio bands, and explains the different characteristics between the common 2.4GHz ISM band and the lesser used 900 and 869 MHz bands in industrial environments.
By John White, Elpro Technologies

THE USE of wireless devices is heavily regulated throughout the world. Each country has a government department responsible for deciding where and how wireless devices can be used, and in what parts of the radio spectrum. Most countries (but not all) have allocated parts of the spectrum for open use, or “license-free” use. Other parts of the spectrum can only be used with permission or “license” for each individual application.

Most wireless products for short-range industrial and commercial applications use the license-free areas of the spectrum, to avoid the delay, cost and hassle of obtaining licenses. The license-free bands are also knows as ISM bands -- “Industrial, Scientific & Medical.”.In many countries there are several ISM bands available, in different parts of the spectrum.