RBU is a time code radio station located in Moscow ().
It transmits a continuous 10 kW time code on 66⅔ kHz.
[ Supplement to Recommendation ITU-R TF.768 "Standard frequencies and time signals".] This is commonly written as 66.66
or 66.666 kHz, but is actually 200/3 kHz.
Until 2008, the transmitter site was near Kupavna and used as antenna three T-antennas spun between three 150 metres tall grounded masts. In 2008, it has been transferred to the
Taldom transmitter
Taldom transmitter (russian: переда́тчик Та́лдом) is a large facility for longwave and shortwave broadcasting located near Taldom, Russia. It transmits on two longwave frequencies, on 153 kHz with 300 kW and on 261&nb ...
at .
RBU is controlled by
. It is operated by
Russian Television and Radio Broadcasting Network
Russian Television and Radio Broadcasting Network (RTRN) (russian: Российская телевизионная и радиовещательная сеть) is a unitary enterprise created on August 13, 2001, by decree of the president of t ...
.
Time code
Every 100 ms, synchronized to the UTC second, one bit is transmitted:
100 Hz modulation encodes a binary 0, while 312.5 Hz modulation encodes a binary 1.
Each UTC second consists of 10 such bits. 6 of them are fixed, two encode minute boundaries, and two provide time code information:
Each minute, the two bits of time code encode the local time of the following minute (like
DCF77) and some additional information. Because the time code starts with two 1 bits, the top of the minute is uniquely marked by 5 consecutive 1 bits.
[Se]
Nils Schiffhauer's radio monitoring pages
Under "Audio Clips — Medium Wave (& Longwave)" are audio samples of several time signal stations, including both an audio clip and a spectrogram "waterfall diagram
Waterfall plots are often used to show how two-dimensional phenomena change over time. A three-dimensional ''spectral waterfall plot'' is a plot in which multiple curves of data, typically spectra, are displayed simultaneously. Typically the cu ...
" of RBU at the top of the hour. It clearly shows the 0.1 second bits producing sideband
In radio communications, a sideband is a band of frequencies higher than or lower than the carrier frequency, that are the result of the modulation process. The sidebands carry the information transmitted by the radio signal. The sidebands ...
s straddling the carrier at ±100 Hz and ±312.5 Hz, and the 5 consecutive 1 bits marking the top of the minute. The carrier has been shifted down by 66.0 kHz, so it shows up on the plot at 666⅔ Hz.
dUT1 is an additional, higher-precision correction to DUT1. UT1 = UTC + DUT1 + dUT1.
Bits with a weight of ± are 0 for positive, 1 for negative. The time transmitted is Moscow local time;
UTC can be computed by subtracting the value of the ΔUT field.
References
{{Time signal authorities
Time signal radio stations
Time in Russia
Call signs