UHF

From AB9RF

UHF is short for Ultra High Frequency, and refers to any signal between 300 MHz and 3 GHz (3000 MHz).

The UHF bands authorized in the United States at present are the 70 centimeter, 33 centimeter, 23 centimeter, and 13 centimeter bands. These bands are much wider than the lower-frequency VHF and HF bands.

UHF frequencies do not, except under extraordinarily unusual circumstances, propagate by way of reflection within the ionosphere, and these bands are almost exclusively limited to line-of-sight operation. UHF radios feature much smaller antennas than those required by VHF radios, but until recently have not been widely available because of the high cost and difficulty in fabrication of the radios. Modern advances in semiconductor fabrication and other technologies have enabled the cost-effective production of radios at increasingly higher frequencies over the past decades (a phenomenon evident in areas other than ham radio, as well), and these days a UHF radio costs about the same as a VHF radio.

The relatively large amount of spectrum available combined with the relatively low cost of radios and of antennas has made the 70 centimeter UHF band a very popular one for FM voice repeaterss. The higher-frequency 33 centimeter and 23 centimeter bands are starting to find more use; the latter is especially popular for the digital voice modulations known as D*STAR. The 13 centimeter band is not as heavily used, in part because it partially overlaps a ISM band, and more specifically the band used by 802.11 wireless computer networking.