Editing Relay league (section)

== Radio relay leagues ==
[[Amateur radio|Radio amateur]]s have been early in arranging relay leagues, as is reflected in the name of the organization of [[American Radio Relay League]] (ARRL).

Radio amateur message relay operations were originally conducted in the first two decades of the 20th century using [[Morse code]] via [[spark-gap transmitter]]s. As [[vacuum tube]]s became affordable, operations shifted to more efficient manual telegraphy transmitters, referred to as ''CW'' ([[Continuous wave]]). Messages were relayed station-to-station, typically involving four or more re-transmission cycles to cover the continental [[United States]], in an organized system of amateur radio networks. After [[World War II]], voice and [[radioteletype]] implementations of the message relay system were employed.