Amateur radio frequency allocations

Radio amateurs use a variety of transmission modes, including Morse code, radioteletype, data, and voice.

[1] 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.

A signal transmitted on VHF from a hand-held portable will typically travel about 5–10 km (3–6 miles) depending on terrain.

With a large antenna system like a long yagi, and higher power (typically 100 watts or more) contacts of around 1 000 km (600 miles) using the Morse code (CW) and single-sideband (SSB) 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.

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.

These islands of intense ionization are called "sporadic E" and result in erratic but often strong propagation characteristics on the "low[er] band" VHF radio frequencies.

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 (miles) due to these unique weather conditions.

For example: The longest distance reported contact due to tropospheric refraction on 2 metres is 4 754 km (2 954 miles) between Hawaii and a ship south of Mexico.

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.

This enhancement is known as TE, or trans-equatorial propagation and (usually) occurs at latitudes 2 500–3 000 km (1500–1900 miles) within either side of the equator.

[5] An intense solar storm causing aurora borealis (northern lights) will also provide occasional propagation enhancement to HF-low (6-metre) band radio waves.

The mode requires moderately high power (more than 500 watts) and a fairly large, high-gain antenna because round-trip path loss is on the order of 270 dB for 70 cm signals.

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.

For ITU region 1, Radio Society of Great Britain's band plan will be more definitive (click on the buttons at the bottom of the page).

The frequency allocations for hams in ITU Region 2 are: The primary (first priority) user of the channelled 60 meter band is the U.S. National Telecommunications and Information Administration (NTIA).

Effective 5 March 2012 the FCC permits CW, USB, and certain digital modes on these frequencies by amateurs on a secondary basis.

The FCC Report and Order permits the use of digital modes that comply with emission designator “60H0J2B”, which includes PSK31 as well as any RTTY signal with a bandwidth of less than 60 Hz.

Under the International Telecommunication Union's rules, all amateur radio operations may only occur within 50 kilometres (31 mi) of the Earth's surface.