Amateur radio frequency allocations

Amateur radio frequency allocation is done by national telecommunications authorities. Globally, the ITU oversees how much radio spectrum is set aside for amateur radiotransmissions.

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 modes and types of allocations within each range of frequencies is called a bandplan, and may be set by international agreements, national regulations, or agreements between amateur radio operators.

Amateur radio operators should first consult their local regulatory body for further information. Some bands may not available or may have restrictions on usage in certain countries or regions.

FCC Part 97.301 (courtesy of ARRL) includes a table comparing frequency allocations for all three regions.

Band characteristics

[edit]Medium frequency

See also: Medium frequency

• 160 meters – 1.8-2 MHz(1800–2000 kHz) – Often taken up as a technical challenge in a manner similar to 6m. Most useful at night, though notoriously noisy. In many locations, a separate specialized receive-only antenna (such as a shielded loop) is necessary for successful operation on the band. Also known as the "top band" and the "Gentlemen's Band", in apparent contrast to the supposedly freewheeling 80m allocation. Allocations in this band vary widely from country to country.

[edit]High frequency

See also: High frequency

• 80 meters – 3.5-4 MHz (3500–4000 kHz) – Best at night, with significant daytime signal absorption. Works best in winter due to atmospheric noise in summer. Only countries in the Americas and few others have access to all of this band, in other parts of the world amateurs are limited to the bottom 300 kHz or less. In the US and Canada the upper end of the subband from 3600–4000 kHz, which permits use of single-sideband voice, is often referred to as 75 meters. Operators in this sub-band have a reputation for rowdiness similar to CB operators.
• 60 meters – 5 MHz region – A relatively new allocation and only available in a small number of countries such as the United States, United Kingdom, Norway and Iceland. In most countries, the allocation is channelized, and in the USA it is mandatory to operate in upper sideband mode.
• 40 meters – 7.0–7.3 MHz – Considered the most reliable all-season DX band, and most popular at night, and extremely useful for medium distance contacts during the day. Much of this band is shared with broadcasters, and in most countries only the bottom 100 kHz or 200 kHz are available to amateurs.
• 30 meters – 10.1–10.15 MHz – a very narrow band, which is shared with non-amateur services. It is recommended that only Morse Code and data transmissions be used here, and in some countries amateur voice transmission is actually prohibited. Not released for amateur use in a small number of countries. Due to its location in the centre of the shortwave spectrum, provides significant opportunities for long-distance communication at all points of the solar cycle. 30 meters is a WARC band. "WARC" bands are so called due to the specialWorld Administrative Radio Conference allocation of these newer bands to amateur radio use. Almost all radio amateur contests are not allowed on all three WARC bands.
• 20 meters – 14.0–14.35 MHz – Considered the most popular DX band; usually most popular during daytime. QRP operators recognize 14.060 MHz as their primary calling frequency in that band. Users of the PSK31 data mode tend to congregate around 14.071 MHz. Analog SSTV activity is centered around 14.230 MHz.
• 17 meters – 18.068–18.168 MHz – Similar to 20m, but more sensitive to solar conditions. It is often used for extended, informal chats known as "ragchews". 17 meters is a WARC band.
• 15 meters – 21–21.45 MHz – Most useful during solar maximum, and generally a daytime band.
• 12 meters – 24.89–24.99 MHz – Mostly useful during daytime, but opens up for DX activity at night during solar maximum. 12 meters is a WARC band.
• 10 meters – 28–29.7 MHz – Best activity is during solar maximum; during periods of moderate solar activity the best activity is found at low latitudes. The band offers useful short- to medium-range groundwave propagation, day or night. Also the site of frequent illegal unlicensed operation ("bootlegging") and freeband activity by operators using modified Citizen's Bandor amateur radio equipment.

[edit]Characteristics above HF

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 VHF signal transmitted from a hand-held walkie-talkie 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 (typically 100 or more watts) contacts of around 1000 km are common. Ham operators seek to exploit the limits of the frequencies' usual characteristics looking to learn and experiment with radio technology. They also seek to take advantage of "band openings" where due to various natural occurrences, radio emissions can travel well over their normal characteristics. There are numerous causes for these band openings and many hams listen for hours to take advantage of their rare manifestations, which may be of fleeting duration.

Some openings are caused by intense ionization of the upper atmosphere, known as the ionosphere. Other band openings are caused by a weather phenomenon known as an inversion layer, where warm air traps colder air beneath it, which forces the radio emission to travel over long weather layers. Radio signals can travel hundreds or even thousands of kilometres due to these weather layers.

For example, the longest distance contact reported due to tropospheric refraction on 2 meters is 4754 km between Hawai'i and a ship south of Mexico, with reports of one way reception of signals from Réunion to Western Australia, a distance of more than 6000 km. ^[2]

Ionospheric, or skywave propagaton also occurs on 6, 4 and 2 meters, and very occasionally on higher frequencies. The longest terrestrial contact ever reported on 2 meters was between a station in Italy and one in South Africa, at a distance of 7784 km, using anomalous enhancement of the inonosphere over the geomagnetic equator.