Medium Wave Band Information
Mediumwave (MW) radio, also called Medium frequency (MF), in Ameria it is usually referred to as the "AM Band", is a common band for broadcasting. The standard AM broadcast band is 530 kHz to 1710 kHz in North America and Australia, but remains only up to 1610 kHz elsewhere.
Mediumwave signals have the property of following the curvature of the earth (the groundwave) at all times, and also reflecting off the ionosphere at night (skywave). This makes this frequency band ideal for both local and continent-wide service, depending on the time of day. The effectiveness of groundwave signals largely depends on ground conductivity higher conductivity results in better propagation.
In most of the Americas, mediumwave stations are separated by 10 kHz and have two sidebands of ±5 kHz. In the rest of the world, the separation is 9 kHz, with sidebands of ±4.5 kHz. In the US the maximum transmitter power is restricted to 50 kilowatts, while in Europe there are medium wave stations with transmitter power up to 2.5 megawatts.
In Europe, each country is allocated a number of frequencies on which high power (up to 2.5 MW) can be used; the maximum power is also subject to international agreement. In most cases there are two power limits: a lower one for omnidirectional and a higher one with directional radiation with minimums showing toward certain directions. The power limit can also be depending on daytime and it is possible, that a station may not work at nighttime, because it would then produce too much interference. Other countries may only operate low-powered transmitters on the same frequency, again subject to agreement. International mediumwave broadcasting in Europe has decreased markedly with the end of the Cold War and the increased availability of satellite and Internet TV and radio, although the cross-border reception of neighboring countries' broadcasts by expatriates and other interested listeners still takes place.
Due to the high demand for frequencies in Europe, many countries operate single frequency networks; in Britain, BBC Radio Five Live broadcasts from various transmitters on either 693 or 909 kHz. These transmitters are carefully synchronized to minimize interference from more distant transmitters on the same frequency.
Stereo transmission is possible and offered by some stations in the U.S., Canada, Australia, South Africa, and France. However, there are multiple standards for AM stereo with C-QUAM being the legally-permitted one in the United States, and receivers that implement the technologies are relatively rare but not uncommon.
In September 2002, the United States Federal Communications Commission approved the proprietary iBiquity in-band on-channel (IBOC) HD Radio system of digital audio broadcasting, which is meant to improve the audio quality of signals. The Digital Radio Mondiale (DRM) IBOC system has been approved by the ITU for use outside North America and U.S. territories.
As aerials mostly mast radiators are used. Stations broadcasting with low power commonly use masts with heights of a quarter wavelength, while high power stations mostly use half wavelength. The usage of masts longer than 5/8 of radiated wavelength gives a bad radiation pattern. Usually mast antennas are insulated against ground and show a high voltage against ground during transmission, which complicates maintenance, installation of air safety warning lights or using the mast as a tower for UHF/VHF-radio, but there are several ways to use grounded masts or towers.If grounded masts or towers are required, then cage aerials or longwire aerials are used. Another possibility consists of feeding the mast or the tower by cables running from the tuning unit to the guys or crossbars in a certain height. Directional aerials consist of multiple masts, which need not to be from the same height. It is also possible to realize directional aerials for mediumwave with cage aerials where some parts of the cage are fed with a certain phase difference.
Other type of aerials sometimes used for mediumwave are T- and L-aerials and slopers. The kind used depends on the need for grounded or insulated towers. In some cases dipole aerials are used, which are hung between two masts or towers. Such aerials radiate toward the sky.
Please select a frequency from the menu on the right hand side to find more information about stations, including locations, for each frequency.
