Rochelle, New York, reported making nightly entertainment broadcasts over his Special Amateur station, 2ZK, from December 1916 until the following February.

The outbreak of World War One largely suspended the development of civilian radio. However, during this period major improvements were made in vacuum-tube technology, which went into service after the end of wartime restrictions. All of the following examples used vacuum-tube transmitters:
*After the wartime restrictions were lifted, Lee de Forest relicenced 2XG, his New York