On Dec. 24, 1906, Reginald Fessenden transmitted an audio broadcast of spoken voice and music to a few listeners. It was a broadcast in that it was not meant as a point-to-point message. Since then, radio has grown in its scope and coverage, and the technology used to create it has provided the tools to improve it and allow it to extend beyond the traditional airwaves.

Last month, we profiled the event and the innovator. This month, we detail the top 100 technical innovations that have influenced radio, as nominated by you, the reader, and organized by a panel of radio broadcast engineers. The entries for 100 through 21 are listed alphabetically. The top 20 are ranked in order. You may feel that we left something out or that something is not being given the ranking that it deserves. If so, tell us about it at radio@penton.com.
— Chriss Scherer, editor

Technology descriptions by Doug Irwin

100 to 21*

* These are in alphabetical order.