radiotelegraph station
21Etymology of ham radio — Ham is an informal term for an amateur radio operator, and, by extension, ham radio refers to amateur radio in general. This use of the word first appeared in the United States during the opening decade of the twentieth century mdash; for example …
22Signal Corps (United States Army) — U.S. Army Signal Corps Coat of Arms Active 3 March 1863 – Present Country …
23Arc converter — The arc converter, sometimes called the arc transmitter or Poulsen arc after its inventor Valdemar Poulsen, is a device used to convert DC energy into RF energy. It is now on the list of IEEE Milestones as a historic achievement in electrical… …
24Фридман, Уильям Фредерик — Уильям Фредерик Фридман William Frederick Friedman …
25Timeline of historic inventions — The timeline of historic inventions is a chronological list of particularly important or significant technological inventions. Note: Dates for inventions are often controversial. Inventions are often invented by several inventors around the same… …
26Ocean Bluff-Brant Rock, Massachusetts —   CDP   Coordinates …
27CQ (call) — CQ is a code used by wireless operators, particularly those communicating in Morse code, but also by voice operators, to make a general call (called a CQ call ). Transmitting the letters CQ on a particular radio frequency is an invitation for any …
