RBU is a time code radio station located in Moscow (Coordinates: ). It transmits a continuous 10 kW time code on 66⅔ kHz. 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 at .
RBU is controlled by All-Russian Scientific Research Institute for Physical-Engineering and Radiotechnical Metrology. It is operated by Russian Television and Radio Broadcasting Network.
Every 100 ms, synchronized to the UTC second, one bit is transmitted:
|+0 ms||10 ms||Unmodulated carrier|
|+10 ms||80 ms||Carrier PM modulated with 100 Hz or 312.5 Hz tone, modulation index 0.698|
|+90 ms||5 ms||Unmodulated carrier|
|+95 ms||5 ms||Carrier off|
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:
|0 ms||Time code data bit 1|
|100 ms||Time code data bit 2|
|200 ms||Always 0 (100 Hz tone)|
|700 ms||Always 0, except 1 before start of minute|
|900 ms||Always 1 (312.5 Hz tone)|
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.
|Second||Data bit 1||Data bit 2||Second||Data bit 1||Data bit 2|
|00||1||Always 1||1||Always 1||30||4||Year
bit set if
DUT1 ≥ Weight
Bit set if
dUT1 ≥ Weight
|08||0||Unused, zero||+0.8||38||4||Day of week
bit set if
DUT1 ≤ Weight
Bit set if
dUT1 ≤ Weight
|−0.3||41||20||Day of month
Fixed +3 since
26 Oct 2014
Last 4 digits of
|19||10||4000||49||8||P1||TJD bits 18–25||Even|
|20||8||2000||50||4||P2||TJD bits 26–33|
|P3||ΔUT bits 18–23|
|24||0||Unused, zero||200||54||20||P4||Year bits 25–32|
|100||55||10||P5||Month/DoW bits 33–40|
|26||40||80||56||8||P6||Day bits 41–46|
|27||20||40||57||4||P7||Hour bits 47–52|
|28||10||20||58||2||P8||Minute bits 53–59|
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.
- Markus Kuhn (2006-05-10), Low-frequency radio time signals, retrieved 2011-09-20
- International Telecommunication Union (6 October 2010), Characteristics of standard-frequency and time-signal emissions in allocated bands and characteristics of stations emitting with regular schedules with stabilized frequencies, outside of allocated bands, retrieved 2014-10-30 Supplement to Recommendation ITU-R TF.768 "Standard frequencies and time signals".
- William Hepburn (2006-10-29), VLF time signal brioadcasts, retrieved 2011-09-20
- "Москва". Vcfm.ru. Retrieved 2012-10-24.
- "Главный Метрологический Центр Государственной Службы Времени и Частоты (ГМЦ ГСВЧ (НИО-7))". VNIIFTRI. Retrieved 23 July 2018.
- Klaus Betke (1 August 2002), Standard Frequency and Time Signal Stations on Longwave and Shortwave (PDF), pp. 16–17, retrieved 2011-09-20. Note that there is a modulation type error in this reference.
- Standard Time and Frequency Signals (PDF), pp. 5–6, 18–20, retrieved 2018-07-15 -- official signal specification, in russian.
- See 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" of RBU at the top of the hour. It clearly shows the 0.1 second bits producing sidebands 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.
- National Geospatial-Intelligence Agency (2005), PUB 117: Radio Navigation Aids, pp. 2–5, retrieved 2011-09-20