Many thanks to SRAA contributor, Richard Langley, who notes:
Live recording of Radio Reloj (CMBD), Havana, Cuba, on 30 August 2015 beginning at about 15:55 UTC on a frequency of 950 kHz. The signal originates from a 10 kW transmitter at Arroyo Arenas / San Augustin, near Havana, using the Centros Transmisores de Ondas Medias 1 (CTOM1) non-directional antenna facility.
(Radio Reloj can be heard on various frequencies in the AM and FM bands in Cuba and live on the Internet at http://media.enet.cu/radioreloj.)
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.
The time signals in this particular broadcast were well within one second of the time given by a computer's clock synchronized to the U.S. time standard using Network Time Protocol.
The broadcast was received on a Tecsun PL-880 receiver with its built-in loop antenna in Key West, Florida, using an RF bandwidth of 5 kHz. The receiver was oriented for maximum signal strength. Signal quality is generally good. However, there are repeated static crashes (QRN) from thunderstorms in the region.
Richard also notes that he was located in Key West, Florida, using a "Tecsun PL-880 receiver with built-in loop antenna using an RF bandwidth of 5 kHz. The receiver was oriented for maximum signal strength."
