UHF in radio communications stands for ‘Ultra High Frequency’
The UHF frequency band covers the range between 300 – 3000 Mhz (Mega Hertz).
UHF in radio communications is particularly useful in built up area such as cities, as the ‘wavelength’ is shorter the higher up in frequency you go. This means that the shorter wavelength (compared to VHF) allows the signal to theoretically go round and through objects better.
Another advantage is that the aerials are shorter than with vhf equipment (remember higher frequency = shorter wavelength = shorter aerial). This is particularly useful for discreet and covert police operations. Shop security radios are also normally UHF.
A theoretical disadvantage of UHF compared to VHF is a shorter transmission range, though there are lots of factors involved in deciding which system will work best, and UHF systems can be made to go long distances (worldwide in fact) by using it in combination with the latest internet combined technologies.