The High frequency reference article from the English Wikipedia on 24-Jul-2004 (provided by Fixed Reference: snapshots of Wikipedia from wikipedia.org)

High frequency

High frequency (HF) radio frequencies are between 3 and 30 MHz. This range is often called shortwave.

Since the ionosphere often refracts HF radio waves quite well, this range is extensively used for medium and long range terrestrial radio communication. However, suitability of this portion of the spectrum for such communication varies greatly with a complex combination of factors:

• Sunlight/darkness at site of transmission and reception
• Transmitter/receiver proximity to terminator
• Season
• Sunspot cycle
• Solar activity
• Polar aurora
• Maximum usable frequency
• Lowest usable frequency
• Frequency of operation within the HF range

HF is often used for continuous wave morse code transmissions.

See also: VHF, AM radio, Radio propagation

Radio spectrum ELF | SLF | ULF | VLF | LF/LW | MF/MW | HF/SW | VHF | UHF | SHF | EHF 3Hz | 30Hz | 300Hz | 3kHz | 30kHz | 300kHz | 3MHz | 30MHz | 300MHz | 3GHz | 30GHz | 300GHz

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