Traditional radio has been somewhat displaced by the dynamism of the web, to the point that more and more stations are willing to share a stream online. Last year we published a list of the best sites to listen to online radio without sacrificing audio quality, but the concept of "high fidelity" is much older than we think. The first experiments take us back to the 1930s, when the FCC authorized the development of the Apex band, a kind of super AM located between 41 and 44 MHz.
The year was 1937. The technology we simply know as radio today had exploded in popularity and availability, beyond the difficulties in determining who truly invented it. Amplitude modulation was effective, but it was not immune to certain technical details such as static, interference, the influence of weather (especially in the case of electrical storms), and the low quality of its audio. At that time, the AM band across the pond was divided into 96 channels between 550 and 1,500 kHz, with 10 kHz spacing. The FCC, which had been created in 1934 as the successor to the FRC, had the titanic task of preventing all these radios from conflicting. Technological advances allowed experts to discover that beyond 20 MHz, propagation effects were minimal, something the FCC viewed favorably. Transmissions would be more limited, but at the same time consistent throughout the day, they would only reach local communities, and they would enable frequency reuse among multiple stations across the United States. This exploration of higher frequencies in the following years (with multiple tests on experimental stations) finally led to the official announcement of the Apex band.
The Apex Band in Detail
In essence, the Apex band consisted of 75 channels between 41.02 and 43.98 MHz, each separated by 40 kHz, four times more than the 10 kHz of conventional AM. This resulted in less adjacent interference and greater available bandwidth for transmissions that sounded much better despite still being classified as AM. The first 25 channels were reserved with the aim of providing space for educational and non-commercial content, but its adoption was lukewarm at best. By 1939, the FCC's suggestion was that Apex stations make the jump to FM, with overwhelming technical superiority in resistance to interference, even under electrical storm conditions.
The End of the Apex Band
The end of the Apex band materialized on January 1, 1941, when the FCC greenlit a new commercial FM band consisting of 40 channels between 42 and 50 MHz (very different from today's 88-108 MHz). The last two stations to abandon the Apex band were WBOE of the Cleveland Board of Education in February 1941 (it completed its transition to FM), and WBKY of the University of Kentucky in June of that same year, which ceased operations due to financial problems. Today, the Apex band is just another rarity within the fascinating world of radio broadcasting. Fortunately there is more to explore, and the truth is we don't need much. With a simple Raspberry Pi you can build your own radio, but if DIY doesn't interest you, you can always delve into the mystery of secret radio emissions.
