Difference Between VHF & UHF

by Adrian Grahams Google

    The terms Very High Frequency and Ultra High Frequency describe distinct parts of the electromagnetic waveband used for radio and television broadcasts. The main difference between them is that UHF operates on much higher frequencies than VHF. If you're planning to buy a TV antenna, you'll usually need equipment that works on both UHF and VHF wavebands to view all locally available over-the-air digital-television stations.

    Function

    UHF and VHF wavebands are both used by TV stations to broadcast digital-television signals that you can receive with an antenna connected to a TV set, converter box or personal video recorder via a run of coaxial cable. The receiver equipment includes an integrated digital tuner that converts the information carried by the signal into the video that you view on the TV screen and the audio that you hear through the TV's speakers or a connected audio system.

    History and Channel Allocation

    When regular TV broadcasts started in the U.S. in the late 1920s, the Federal Communications Commission allocated 12 channels in the VHF band for television transmissions. However, television broadcasting grew quickly after World War II and the FCC created more capacity for broadcasters by allocating the additional channels in the UHF waveband. Some of the original channels have been reassigned for other purposes and VHF TV signals now broadcast on channels 2 to 13, while UHF TV signals use the higher-frequency channels 14 to 51.

    Reception

    Most TV antennas are directional, which means you need to point the antenna at the TV transmitter to receive a signal that's strong enough for good viewing. UHF transmissions are more directional than VHF transmissions, so UHF antennas usually need more precise alignment than VHF-only antennas. VHF signals also travel further from the transmitter than UHF signals, making reception easier at greater distances from the transmitter or in areas screened by mountains, tall buildings or other obstacles. An advantage of UHF reception is that it's more resistant to certain types interference than VHF.

    Antenna Installation

    Because VHF and UHF antennas use different frequencies, each antenna type is designed and constructed to receive the correct waveband. TV broadcasters in the United States use both VHF and UHF frequencies to offer as many over-the-air channels as possible, so you’ll usually need a combined VHF/UHF antenna to receive all digital stations. Check your local TV reception conditions before purchasing a TV antenna. Use a free online TV signal locator service to find the optimal antenna type for your neighborhood (links in Resources.) Although small set-top antennas may work in strong signal areas close to TV transmitters, most people require a properly aligned directional UHF/VHF antenna mounted in the attic or externally on a rooftop, wall or gable-end. Use a high-grade, digital-television coaxial cable to connect the antenna to the receiver equipment to minimize signal loss.

    About the Author

    Adrian Grahams began writing professionally in 1989 after training as a newspaper reporter. His work has been published online and in various newspapers, including "The Cornish Times" and "The Sunday Independent." Grahams specializes in technology and communications. He holds a Bachelor of Science, postgraduate diplomas in journalism and website design and is studying for an MBA.

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