MW DX, short for mediumwave DXing, is the hobby of receiving distant mediumwave (also known as AM) radio stations. MW DX is similar to TV and FM DX in that broadcast band (BCB) stations are the reception targets. However, the nature of the lower frequencies (530 – 1710 kHz) used by mediumwave radio stations is very much different from that of the VHF and UHF bands used by FM and TV broadcast stations, and therefore involves different receiving equipment, signal propagation, and reception techniques. Propagation During the daytime, medium and high-powered mediumwave AM radio stations have a normal reception range of about 20 to 250 miles (32 to 400+ km), depending on the transmitter power, location, and the quality of the receiving equipment, including the amount of man-made and natural electromagnetic noise present. Long-distance reception is normally impeded by the D layer of the ionosphere, which during the daylight hours absorbs signals in the mediumwave range. As the sun sets, the D layer weakens, allowing medium wave radio waves from such stations to bounce off the F layer of the ionosphere, producing reliable, long distance reception of (especially) high-powered stations up to about 1,200 miles (2,000 km) away on a nightly basis. Aside from the more or less regular reception of certain high-powered transmitters, variable conditions allow reception of different stations at different times - for example, on one night a medium-powered broadcaster from Cleveland, Ohio may be audible in Duluth, Minnesota, but not on the following night. Much of the hobby consists in trying to receive and log as many of these stations as possible, identifying target stations and frequencies to listen to and log. Near or on the coastlines, trans-oceanic reception is quite common and a favored target of DXers in those areas. Very distant inter-continental DX from stations several thousands of miles away is possible even far inland, but may require exceptionally good conditions and a good receiver and antenna on the listening side. DX stations evaporate from the dial as the sun rises. However, sunrise and sunset ("SRS" and "SSS") periods can provide interesting loggings. MW DX in North America In the United States and Canada, stations on the mediumwave dial are spaced at 10 kHz intervals from 520 to 1710 kHz as prescribed since 1941 by the North American Regional Broadcasting Agreement. The tremendous number of radio stations in this region of the world and