<P> In 1933, FM radio was patented by inventor Edwin H. Armstrong . FM uses frequency modulation of the radio wave to reduce static and interference from electrical equipment and the atmosphere . In 1937, W1XOJ, the first experimental FM radio station, was granted a construction permit by the US Federal Communications Commission (FCC). In the 1930s, regular analog television broadcasting began in some parts of Europe and North America . By the end of the decade there were roughly 25,000 all - electronic television receivers in existence worldwide, the majority of them in the UK . In the US, Armstrong's FM system was designated by the FCC to transmit and receive television sound . </P> <P> After World War II, FM radio broadcasting was introduced in Germany . At a meeting in Copenhagen in 1948, a new wavelength plan was set up for Europe . Because of the recent war, Germany (which did not exist as a state and so was not invited) was only given a small number of medium - wave frequencies, which were not very good for broadcasting . For this reason Germany began broadcasting on UKW ("Ultrakurzwelle", i.e. ultra short wave, nowadays called VHF) which was not covered by the Copenhagen plan . After some amplitude modulation experience with VHF, it was realized that FM radio was a much better alternative for VHF radio than AM . Because of this history FM Radio is still referred to as "UKW Radio" in Germany . Other European nations followed a bit later, when the superior sound quality of FM and the ability to run many more local stations because of the more limited range of VHF broadcasts were realized . </P> <P> In 1954 Regency introduced a pocket transistor radio, the TR - 1, powered by a "standard 22.5 V Battery". In the early 1960s, VOR systems finally became widespread for aircraft navigation; before that, aircraft used commercial AM radio stations for navigation . (AM stations are still marked on U.S. aviation charts). In 1960 Sony introduced their first transistorized radio, small enough to fit in a vest pocket, and able to be powered by a small battery . It was durable, because there were no tubes to burn out . Over the next twenty years, transistors displaced tubes almost completely except for picture tubes and very high power or very high frequency uses . </P> <Ul> <Li> 1953: NTSC compatible color television introduced in the US . </Li> <Li> 1962: Telstar 1, the first communications satellite, relayed the first publicly available live transatlantic television signal . </Li> <Li> Late 1960s: The US long - distance telephone network began to convert to a digital network, employing digital radios for many of its links . </Li> <Li> 1970s: LORAN became the premier radio navigation system . Soon, the US Navy experimented with satellite navigation . </Li> <Li> 1987: The GPS constellation of satellites was launched . </Li> <Li> Early 1990s: Amateur radio experimenters began to use personal computers with audio cards to process radio signals . </Li> <Li> 1994: The US Army and DARPA launched an aggressive successful project to construct a software radio that could become a different radio on the fly by changing software . </Li> <Li> Late 1990s: Digital transmissions began to be applied to broadcasting . </Li> <Li> 2015: The first all - digital radio transmitter, called Pizzicato, was introduced . </Li> </Ul>

When were the first three commercial radio stations established