"DX" and "QSL" : These terms started as Morse Code "words." DX is an acronym for "distant" and refers to stations distant from the listener. Many DXers send letters to the stations they hear, requesting QSL, or "reception" cards. These cards are then used to verify the listener has heard the station. In the 20's and 30's, stations often sent stamps (not unlike postage stamps) to be placed in a book "collecting" the stations heard. EKKO was one prominent stamp company.