DXing is the hobby of tuning in and identifying distant radio or television signals, or making two way radio contact with distant stations in amateur radio, citizens' band radio or other two way radio communications hobbies. Many DXers also attempt to receive written verifications of reception (sometimes referred to as "QSLs" or "veries") from the stations heard. The name of the hobby comes from DX, telegraphic shorthand for "distance" or "distant".
AM radio DX
Early radio listeners, often using home made crystal sets and long wire antennas, faced the dilemma of radio stations that were few and far between. With the broadcast bands uncrowded, signals of the most powerful stations could be heard over hundreds of miles, but weaker signals required more precise tuning or better receiving gear.
By the 1950's, and continuing through the mid 1970's, many of the most powerful North American "clear channel" stations such as WLW, CKLW, CHUM, WABC, WLS, WKBW, KHJ, KAAY and a host of border blasters from Mexico pumped out Top 40 music played by popular disc jockeys. As most smaller, local AM radio stations had to sign off at night, the big 50 kW stations had loyal listeners hundreds of miles away.
The popularity of DXing the medium-wave band has diminished as the popular music formats quickly migrated to the clearer, though less propagating, FM radio beginning in the 1970's. Meanwhile, the MW band in the United States was getting more and more crowded with new stations and existing stations receiving FCC authorization to operate at night. In Canada, just the opposite occurred as AM stations began moving to FM beginning in the 1980's and continuing through today.
Outside of the Americas and Australia, most AM radio broadcasting was in the form of synchronous networks of government-operated stations, operating with hundreds, even thousands of kilowatts of power. Still, the lower powered stations and occasional Trans-oceanic signal were popular DX targets.
Especially during wartime and times of conflict, reception of international broadcasters, whose signals propagate around the world on the shortwave bands has been popular with both casual listeners and DXing hobbyists.
With the rise in popularity of streaming audio over the Internet, many international broadcasters (including the BBC and Voice of America) have cut back on their shortwave broadcasts. An active religious missionary broadcasting scene still makes extensive use of shortwave radio to reach less developed countries around the world.
In addition to international broadcasters, the shortwave bands also are home to military communications, RTTY, amateur radio, pirate radio, and the mysterious broadcasts of numbers stations. Many of these signals are transmitted in single side band mode, which requires the use of specialized receivers more suitable to DXing than to casual listening.
Though sporadic in nature, signals on the FM broadcast and VHF television bands - especially those stations at the lower end of these bands - can "skip" for hundreds, even thousands of miles. American FM stations have been occasionally received in Western Europe, though no reports exist of European FM signals propagating to North America.
Police, fire, and military communications on the VHF bands are also DX'ed to some extent on multi-band radio scanners, though they are mainly listened to strictly on a local basis. One element of this is that communications of this nature are much harder to identify the exact origins of, as opposed to commercial broadcasters which must identify themselves at the top of each hour, and can often be identified through mentions of sponsors, slogans, etc. throughout their programming.
Although the classic definition of DX is "distance", today it generally means contacting amateur radio stations in far-away places. On the HF (also known as shortwave) bands, DX stations are those in foreign countries. On the VHF/UHF bands, DX stations can be within the same country or continent, since making a long-distance VHF contact, without the help of a satellite, can be very difficult.
For award purposes, other areas than just political countries can be classified as "DX countries". For example, the French protectorate of Reunion Island in the Indian Ocean is counted as a DX country, even though it is a department of France. The rules for determining what is a DX country can be quite complex and to avoid potential confusion, radio amateurs often use the term entity instead of country. In addition to entities, some awards are based on island groups in the world's oceans. On the VHF/UHF bands, many radio amateurs pursue awards based on Maidenhead grid locators.
For the most rare locations, DX-perditions are often organized to allow radio amateurs to "work a new one".
There are frequent contests where radio amateurs operate their stations on certain dates for a fixed period of time to try to communicate with as many DX stations as possible.
In addition, many clubs offer awards for communicating with a certain number of DX stations. For example, the ARRL offers the DX Century Club award, or DXCC. The basic certificate is awarded for working and confirming at least 100 entities on the ARRL DXCC List
Many radio enthusiasts are members of DX clubs. There are many DX clubs in many countries around the world. They are useful places to find information about up-to-date news relating to international radio. Many people also enjoy social events, which can form a large part of the enjoyment that people can get out of the radio hobby.
One of the interesting sides of DXing as a hobby is collecting QSL cards (acknowledgement cards from the broadcaster) confirming the listener's reception report (sometimes called SINPO report-see next section). Usually a QSL card will have a picture on one side and the reception data on the other. Most of the broadcasters will use pictures and messages indicating their country's culture or technological life. In fact these cards are more valuable compared to postal stamps collection of which has already became an international hobby.