The terms "DX" and "DXing" were also used among radio listeners. In broadcasting's earliest days, radio listeners were known as BCLs, for "broadcast listeners," and those BCLs who were interested in listening not for program content but for the thrill of hearing distant stations were called DXers. Their hobby was (and still is) known as DXing, and their goal was to hear as many stations, from the farthest locations, as possible.

     For a time in the early 1920s, long-distance broadcast listening was popular with a large portion of the population. Radio--especially radio from distant places-was a new experience, and everyone wanted to see how far they could "get" with their equipment. However, as the novelty of radio wore off and network broadcasting started, DXing became the preserve mainly of the technically inclined and of hard-core distance aficionados.

     Shortwave broadcasting would not come to the attention of most listening hobbyists until around 1924, and so in the United States most DXing before then was done on the standard broadcast (medium wave) band, with domestic stations the targets. The relatively small number of stations and the resulting absence of the channel blocking that is common today, coupled with the prevalence of daytime-only operations, made it possible for a conscientious, well-equipped night hound to hear a large number of the stations that were operating.

     DXing's attraction was captured by journalist Charlotte Geer in her 1927 poem "Another One":

You may pick out an average young man Who has nothing especial "agin it,"

And draw up a comfortable chair And settle him in it.

Then you mention the call of the West Thus tempting his spirit to roam

That he early may tire of books by the fire The tame little voices of home.

When the chimes of the clock tinkle ten The rest of the folks go to bed,

You must then take the youngster in hand And fasten the phones on his head.

You must lead him and prod him by turns He'll yawn and seem bored and forlorn

Till he hears that first call from the coast­ And behold a DXer is born.

     The "call from the coast" refers to the ability of east-coast listeners, late at night and under the right conditions, to hear stations in California as outlets farther east signed off at local sundown.

     Although pioneer radio fans built their own sets, as the number of DXers increased a distinct market was recognized by equipment manufacturers, and soon radios with special features for long-distance reception were being produced. The most important elements to good reception were sensitivity (the ability to pick up weak signals), selectivity (the ability to separate adjacent signals), and frequency readout (the ability to know what frequency the equipment is tuned to). To meet these needs and the like needs of the amateur radio operators, the communications receiver was developed. These receivers, which appeared beginning in 1933 and continue on the market today, emphasize technical capabilities rather than appearance or simplicity of operation. Among the principal early manufacturers of such sets were Hallicrafters, Hammarlund, and National. Today the major producers of high-quality, semi-professional receivers include Drake, Icom, AOL, and Japan Radio Company.

     With the discovery that shortwave signals could propagate around the globe, what had been, in the United States, largely a search for U.S., Canadian, and Caribbean stations on the standard broadcast band took on a worldwide flavor as DXers tried their hand at the shortwave frequencies. Many countries began international shortwave services, and domestic shortwave broadcasting became commonplace in many foreign countries as well, particularly those with large geographic areas to cover. These latter stations made particularly good DX targets. Some listeners also went outside the broadcasting frequencies, preferring to tune in to amateur radio operators; transmissions from ships, planes, and police; and other users of the shortwave spectrum.

     The need for up-to-date station information led to rhe publication of magazines such as Radio Index, All Wave Radio, and Official Short Wave Listener Magazine. These publications were devoted either entirely or in part to DXing. Other magazines had special sections for long-distance radio enthusiasts. Clubs such as the Newark News Radio Club and the International DXers Alliance were formed, and periodic bulletins containing members' "loggings" and other DX information issued. Special broadcasts were scheduled over stations at times when they might not ordinarily be heard, and contests were held to compare DXing prowess.

     Besides hearing the stations, many DXers collected QSLs. QSL is the telegraph abbreviation for the acknowledgment of receipt of a signal or a message. QSLs are cards or letters that stations issue to DXers, confirming that it was in fact their station that was heard, based on the listener's description of the programming. QSLs usually take the form of distinctive cards and letters containing information about the station and its location. Some DXers also make it a practice to make audio recordings of their DX catches and thus preserve their listening experiences.

     Notwithstanding the common availability of local radio signals over even the simplest equipment, long-distance radio listening still has a devoted following. Although the pervasiveness of high-power, all-night broadcasting has made DXing on the broadcast band more difficult, on the shortwave bands the combination of improved receivers and higher­ power transmitters has led to easier tuning and more reliable reception.

     As a result, whereas DX was the main objective of long-distance radio enthusiasts during most of radio's developmental period, "shortwave listening"-listening for program content rather than distance-is often the purpose today. Some listeners follow particular specialties. On shortwave they may listen to clandestine radio stations; unlicensed pirate stations; or small stations from exotic parts of the world, such as Indonesia or the Andes. On the broadcast band, some listeners concentrate on domestic stations, while others focus on foreign broadcasters.

     Although the number of DXers has declined over the years, there is still much truth in the observation made by radio pioneer Hugo Gernsback in 1926: "I can not imagine any greater thrill," he wrote, "than that which comes to me when I listen, as I often do, to a station thousands -of miles away. It is the greatest triumph yet achieved by mind over matter."