There are a number of other "free use" bands (called ISM bands). See wikipedia[0] for more information. Some of the most interesting ones are at 433 MHz (Europe

There are a number of other "free use" bands (called ISM bands). See wikipedia[0] for more information. Some of the most interesting ones are at 433 MHz (Europe), 902 MHz (US only, often used for old cordless telephones), and 24 GHz (worldwide). We have microwaves to thank for the 2.4 GHz band (and maybe 900 MHz as well)[1]. 0: https://en.wikipedia.org/wiki/ISM_band https://en.wikipedia.org/wiki/ISM_band 1: https://web.archive.org/web/20160304061338/https://www.itu.int/dms_pub/itu-s/oth/02/01/S020100002B4813PDFE.pdf https://web.archive.org/web/20160304061338/https://www.itu.i... (see page 464)