Amateur radio frequency allocations


Amateur radio frequency allocation is done by national telecommunication authorities. Globally, the International Telecommunication Union oversees how much radio spectrum is set aside for amateur radio transmissions. Individual amateur stations are free to use any frequency within authorized frequency ranges; authorized bands may vary by the class of the station license.
Radio amateurs use a variety of transmission modes, including Morse code, radioteletype, data, and voice. Specific frequency allocations vary from country to country and between ITU regions as specified in the current ITU HF frequency allocations for amateur radio. The list of frequency ranges is called a band allocation, which may be set by international agreements, and national regulations. The modes and types of allocations within each frequency band is called a bandplan; it may be determined by regulation, but most typically is set by agreements between amateur radio operators.
National authorities regulate amateur usage of radio bands. Some bands may not be available or may have restrictions on usage in certain countries or regions. International agreements assign amateur radio bands which differ by region.

Band characteristics

Low frequency

  • 2200 metres – 135.7-137.8 kHz

    Medium frequency

  • 630 metres – 472–479 kHz
  • 160 metres –

    High frequency

  • 80 metres or – – 85.65–74.95 m actual
  • 60 metres – 5 MHz region – around 56 m
  • 40 metres – 7.000–7.300 MHz – 42.83–41.51 m actual
  • 30 metres – 10.100–10.150 MHz – 29.68–29.54 m actual
  • 20 metres – 14.000–14.350 MHz – 21.41–20.89 m actual
  • 17 metres – 18.068–18.168 MHz – 16.6–16.5 m actual
  • 15 metres – 21.000–21.450 MHz – 14.28–13.98 m actual
  • 12 metres – 24.890–24.990 MHz – 12.04–12.00 m actual
  • 10 metres – 28.000–29.700 MHz – 10.71–10.08 m actual

    Very-high frequencies and ultra-high frequencies

Frequencies between 30 and 300 MHz are referred to as Very High Frequency region and those between 300 MHz and 3 GHz are referred to as Ultra High Frequency. The allocated bands for amateurs are many megahertz wide, allowing for high-fidelity audio transmission modes and very fast data transmission modes that are unfeasible for the kilohertz-wide allocations in the HF bands.
While "line of sight" propagation is a primary factor for range calculation, much of the interest in the bands above HF comes from use of other propagation modes. A signal transmitted on VHF from a hand-held portable will typically travel about 5–10 km depending on terrain. With a low power home station and a simple antenna, range would be around 50 km.
With a large antenna system like a long yagi, and higher power contacts of around 1 000 km using the Morse code and single-sideband modes are common. Ham operators seek to exploit the limits of the frequencies usual characteristics looking to learn, understand, and experiment with the possibilities of these enhanced propagation modes.

Sporadic band openings

Occasionally, several different ionospheric conditions allow signals to travel beyond the ordinary line-of-sight limits. Some amateurs on VHF seek to take advantage of "band openings" where natural occurrences in the atmosphere and ionosphere extend radio transmission distances well over their normal range. Many hams listen for hours hoping to take advantage of these occasional extended propagation "openings".
The ionospheric conditions are called sporadic E and anomalous enhancement. Less frequently used anomalous modes are tropospheric scatter and Aurora Borealis. Moon bounce and satellite relay are also possible.
Sporadic E
Some openings are caused by islands of intense ionization of the upper atmosphere, known as the E Layer ionosphere. These islands of intense ionization are called "sporadic E" and result in erratic but often strong propagation characteristics on the "low band" VHF radio frequencies.
The 6 metre amateur band falls into this category, often called "the magic band", will often "open up" from one small area into another small geographic area away during the spring and early summer months. This phenomenon occurs during the fall months, although not as often.
Tropospheric refraction
Band openings are sometimes caused by a weather phenomenon known as a tropospheric "inversion", where a stagnant high pressure area causes alternating stratified layers of warm and cold air generally trapping the colder air beneath. This may make for smoggy or foggy days, but it also causes VHF and UHF radio transmissions to travel or duct along the boundaries of these warm/cold atmospheric layers. Radio signals have been known to travel hundreds, even thousands of kilometres due to these unique weather conditions.
For example: The longest distance reported contact due to tropospheric refraction on 2 metres is between Hawaii and a ship south of Mexico. There were reports of the reception of one way signals from Réunion to Western Australia, a distance of more than
Tropo-scatter happens when water droplets and dust particles refract a VHF or UHF signal over the horizon. Using relatively high power and a high gain antenna, this propagation will give marginal enhanced over-the-horizon VHF and UHF communications up to several hundred kilometres. During the 1970s commercial "scatter site" operators using huge parabolic antennas and high power used this mode successfully for telephone communications services into northern remote Alaska and Canadian communities.
Satellite, buried fibre optic, and terrestrial microwave access have relegated commercial use of tropo-scatter to the history books. Because of high cost and complexity this mode is usually out of reach for the average amateur radio operator.
Anomalous trans-equatorial enhancement
F2 and TE band openings from other ionospheric reflection/refraction modes, or sky-wave propagation as it is known can also occasionally occur on the low band VHF frequencies of 6 or 4 metres, and very rarely on 2 metres during extreme peaks in the 11 year sunspot cycle.
The longest terrestrial contact ever reported on 2 metres was between a station in Italy and a station in South Africa, a distance of 7 784 km, using trans-equatorial anomalous enhancement of the ionosphere over the geomagnetic equator. This enhancement is known as TE, or trans-equatorial propagation and occurs at latitudes 2 500–3 000 km within either side of the equator.
Auroral backscatter
An intense solar storm causing aurora borealis will also provide occasional propagation enhancement to HF-low band radio waves. Aurorae only occasionally affect signals on the 2 metre band. Signals are often distorted and on the lower frequencies give a curious "watery sound" to normally propagated HF signals. Peak signals usually come from the north, even if the signal originates from a station to the east or west of the receiver. This effect is most significant in the latitudes north of 45 degrees.
Moon bounce (Earth-Moon-Earth)
Amateurs do successfully communicate by bouncing their signals off the surface of the Moon, called Earth-Moon-Earth transmission.
The mode requires moderately high power and a fairly large, high-gain antenna because round-trip path loss is on the order of 270 dB for 70 cm signals. Return signals are weak and distorted because of the relative velocities of the transmitting station, Moon and the receiving station. The Moon's surface is also very rocky and irregular.
Because of the weak, distorted return signals, Moon bounce communications use digital modes. For example, old-fashioned Morse code or modern JT65, designed for working with weak signals.
Satellite relay
is not really a propagation mode, but rather an active repeater system. Satellites have been highly successful in providing VHF/UHF/SHF users "propagation" beyond the horizon.
Amateurs have sponsored the launch of dozens of communications satellites since the 1970s. These satellites are usually known as OSCARs. Also, the ISS has amateur radio repeaters and radio location services on board.

Amateur television

Amateur television is the hobby of transmitting broadcast-compatible video and audio by amateur radio. It also includes the study and building of such transmitters and receivers and the propagation between these two.
In NTSC countries, ATV operation requires the ability to use a 6 MHz wide channel. All bands at VHF or lower are less than 6 MHz wide, so ATV operation is confined to UHF and up. Bandwidth requirements will vary from this for PAL and SECAM transmissions.
ATV operation in the 70 cm band is particularly popular, because the signals can be received on any cable-ready television. Operation in the 33 cm and 23 cm bands is easily augmented by the availability of various varieties of consumer-grade wireless video devices that exist and operate in unlicensed frequencies coincident to these bands.
Repeater ATV operation requires specially-equipped repeaters.

Below the MW broadcast band

Historically, amateur stations have rarely been allowed to operate on frequencies lower than the medium-wave broadcast band, but in recent times, as the historic users of these low frequencies have been vacating the spectrum, limited space has opened up to allow for new amateur radio allocations and special experimental operations.
Since parts of the 500 kHz band are no longer used for regular maritime communications, some countries permit amateur radio radiotelegraph operations in that band. Many countries, however, continue to restrict these frequencies which were historically reserved for maritime and aviation distress calls.
The band is available for use in several countries, and the 2007 World Radiocommunication Conference recommended it as a worldwide amateur allocation. Before the introduction of the band in the U.K. in 1998, operation on the even lower frequency of 73 kHz, in the LF time signal band, was allowed from 1996–2003.