Editing High frequency (section)

==Uses==
[[File:Amateurfunkstation.jpg|thumb|An amateur radio station incorporating two HF transceivers.]]
[[File:Montreal-tower-top.thumb2-crop.jpg|thumb|A typical [[Yagi antenna]] used by a Canadian radio amateur for long distance communication]]
[[File:SpAF Boeing 707-331B(KC).jpg|thumb|[[Boeing 707]] used a HF antenna mounted on top of the tail fin <ref>{{cite web|url=http://vipclubmn.org/couplers.html|title= The Antenna Coupler Program|author=Shoquist, Marc|publisher=VIP Club}}</ref>]]

The main uses of the high frequency spectrum are:
* Military and governmental communication systems
* Aviation air-to-ground communications
* [[Amateur radio]]
* [[Shortwave]] international and regional broadcasting
* Maritime sea-to-shore and ship-to-ship services
* [[Over-the-horizon radar]] systems
* [[Global Maritime Distress and Safety System]] (GMDSS) communication
* [[Citizen's Band Radio]] services worldwide (generally 26-28&nbsp;MHz, the higher portion of the HF band, that behaves more like low-[[VHF]])
* [[Coastal ocean dynamics applications radar]]

The high frequency band is very popular with [[amateur radio]] operators, who can take advantage of direct, long-distance (often inter-continental) communications and the "thrill factor" resulting from making contacts in variable conditions.  International [[shortwave]] broadcasting utilizes this set of frequencies, as well as a seemingly declining number of "utility" users (marine, aviation, military, and diplomatic interests), who have, in recent years, been swayed over to less volatile means of communication (for example, via [[satellite]]s), but may maintain HF stations after switch-over for back-up purposes.

However, the development of [[Automatic link establishment|Automatic Link Establishment]] technology based on MIL-STD-188-141 for automated connectivity and frequency selection, along with the high costs of satellite usage, have led to a renaissance in HF usage in government networks. The development of higher speed modems such as those conforming to MIL-STD-188-110C which support data rates up to 120 kilobit/s has also increased the usability of HF for data communications and video transmission.  Other standards development such as [[STANAG]] 5066 provides for error free data communications through the use of [[Automatic repeat request|ARQ]] protocols.

Some modes of communication, such as [[continuous wave]] [[Morse code]] transmissions (especially by [[amateur radio]] operators) and [[Single-sideband modulation|single sideband]] voice transmissions are more common in the HF range than on other frequencies, because of their bandwidth-conserving nature, but broadband modes, such as TV transmissions, are generally prohibited by HF's relatively small chunk of [[electromagnetic spectrum]] space.

Noise, especially man-made interference from electronic devices, tends to have a great effect on the HF bands.  In recent years, concerns have risen among certain users of the HF spectrum over "broadband over power lines" ([[Broadband over power lines|BPL]]) [[Internet]] access, which has an almost destructive effect on HF communications.  This is due to the frequencies on which BPL operates (typically corresponding with the HF band) and the tendency for the BPL signal to leak from power lines. Some BPL providers have installed notch filters to block out certain portions of the spectrum (namely the amateur radio bands), but a great amount of controversy over the deployment of this access method remains. Other electronic devices including plasma televisions can also have a detrimental effect on the HF spectrum.

In aviation, HF communication systems are required for all trans-oceanic flights. These systems incorporate frequencies down to 2&nbsp;MHz to include the [[2182 kHz]] international distress and calling channel.

The upper section of HF (26.5-30&nbsp;MHz) shares many characteristics with the lower part of VHF. The parts of this section not allocated to amateur radio are used for local communications. These include [[Citizens band radio|CB radios]] around 27&nbsp;MHz, studio-to-transmitter (STL) radio links, [[radio control]] devices for models and radio paging transmitters. 
  
Some radio frequency identification (RFID) tags utilize HF.  These tags are commonly known as HFID's or HighFID's (High-Frequency Identification).