Radio Reloj: August 30, 2015

The recording, in Spanish, is a typical Radio Reloj broadcast with two announcers alternately reading news bulletins accompanied by time signals. The announcers identify the station and verbally give the local time each minute. In addition to the verbal station identification, each minute either the letters RR in morse code (using 1800 Hz tones) are transmitted or five-note chimes (D4, G4, B4, D5, B4) are played. The chimes sound like those of a dinner chime or even some door bells and are reminiscent of the U.S. National Broadcasting Company (NBC) chimes. On a couple of occasions in this recording, during a particular minute, neither the morse code nor the chimes are used and sometimes, during a particular minute, both are used. In this recording, we can also hear at some minutes pairs of tones being played going up and down the scale as news headlines are read. On other occasions, three- and four-note chimes in various sequences have been heard (perhaps at the announcers' whim).

Different tones identify each second, minute, and five-minute epochs. Based on measurements, each second is marked with a "seconds tick" consisting 10 cycles of a 1000 Hz tone (0.01 seconds duration). Minutes, except for multiples of 5 minutes, are marked by 172 cycles of a 1000 Hz tone (0.172 seconds duration). Every 5 minutes, the marker is extended to 672 cycles of a 1000 Hz tone (0.672 seconds duration). The minute and 5-minute markers are preceded by 5 cycles of a 1000 Hz tone, followed by 0.013 seconds of silence.

Recorded by Richard Langley, courtesy of the Shortwave Radio Archive.

Part of the Shortwave Transmissions project, documenting and reimagining the sounds of shortwave radio - find out more and see the whole project at https://citiesandmemory.com/shortwave