page_title: Ultra high frequency
section_title: Antennas
hierarchical_section_title: Ultra high frequency / Antennas
caption_attribution_description: English: A drawing of a corner reflector UHF television antenna from a 1954 advertisement in an electronics magazine. The corner reflector was a common antenna used for analog UHF TV reception. It consists of a "bow tie" dipole driven element made of a pair of sheet metal triangles suspended between two flat rectangular metal grill reflecting surfaces at an angle of 90°. The corner reflector's advantages were a high gain of 12-15 dBi, a large front-to-back ratio, and a wide bandwidth, much wider than the Yagi antenna. Alterations to image: Cropped out the rest of the advertisement. Cloned in a little of the reflector screen in upper left corner where it was obscured by other picture elements. Added shading to bow-tie dipole to make its shape clearer.
context_page_description: Ultra high frequency is the ITU designation for radio frequencies in the range between 300 megahertz and 3 gigahertz, also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter. Radio waves with frequencies above the UHF band fall into the super-high frequency or microwave frequency range. Lower frequency signals fall into the VHF or lower bands. UHF radio waves propagate mainly by line of sight; they are blocked by hills and large buildings although the transmission through building walls is strong enough for indoor reception. They are used for television broadcasting, cell phones, satellite communication including GPS, personal radio services including Wi-Fi and Bluetooth, walkie-talkies, cordless phones, and numerous other applications.
  The IEEE defines the UHF radar band as frequencies between 300 MHz and 1 GHz. Two other IEEE radar bands overlap the ITU UHF band: the L band between 1 and 2 GHz and the S band between 2 and 4 GHz.
context_section_description: The length of an antenna is related to the length of the radio waves used.  Due to the short wavelengths, UHF antennas are conveniently stubby and short; at UHF frequencies a quarter-wave monopole, the most common omnidirectional antenna is between 2.5 and 25 cm long.  UHF wavelengths are short enough that efficient transmitting antennas are small enough to mount on handheld and mobile devices, so these frequencies are used for two-way land mobile radio systems, such as walkie-talkies, two way radios in vehicles, and for portable wireless devices; cordless phones and cell phones. Omnidirectional UHF antennas used on mobile devices are usually short whips, sleeve dipoles, rubber ducky antennas or the planar inverted F antenna (PIFA) used in cellphones.  Higher gain omnidirectional UHF antennas can be made of collinear arrays of dipoles and are used for mobile base stations and cellular base station antennas.
  The short wavelengths also allow high gain antennas to be conveniently small.  High gain antennas for point-to-point communication links and UHF television reception are usually Yagi, log periodic, corner reflectors, or reflective array antennas. At the top end of the band slot antennas and parabolic dishes become practical. For satellite communication, helical, and turnstile antennas are used since satellites typically employ circular polarization which is not sensitive to the relative orientation of the transmitting and receiving antennas. For television broadcasting specialized vertical radiators that are mostly modifications of the slot antenna or reflective array antenna are used: the slotted cylinder, zig-zag, and panel antennas.
caption: Corner reflector UHF-TV antenna from 1950s
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