RBU_(radio_station)

RBU (radio station)

RBU (radio station)

Time signal transmitter in Russia

RBU is a time code radio station located in Moscow (56°44′00″N 37°39′48″E).[1] It transmits a continuous 10 kW time code on 66⅔ kHz.[2] This is commonly written as 66.66[1] or 66.666 kHz,[3] but is actually 200/3 kHz.[2] Until 2008, the transmitter site was near Kupavna 55°44′04″N 38°9′0″E 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 56°44′00″N 37°39′48″E.[4]

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.[5]

Time code

Every 100 ms, synchronized to the UTC second, one bit is transmitted:

More information Start, Duration ...

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:

More information Start, Significance ...

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.[8]

More information Second, Data bit 1 ...

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

  1. [1]
    Markus Kuhn (2006-05-10), Low-frequency radio time signals, retrieved 2011-09-20
  2. [2]
    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, archived from the original on 2012-11-06, retrieved 2014-10-30 Supplement to Recommendation ITU-R TF.768 "Standard frequencies and time signals".
  3. [3]
    William Hepburn (2006-10-29), VLF time signal brioadcasts, retrieved 2011-09-20
  4. [4]
    "Москва". Vcfm.ru. Retrieved 2012-10-24.
  5. [5]
    "Главный Метрологический Центр Государственной Службы Времени и Частоты (ГМЦ ГСВЧ (НИО-7))". VNIIFTRI. Archived from the original on 27 July 2018. Retrieved 23 July 2018.
  6. [6]
    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.
  7. [7]
    Standard Time and Frequency Signals (PDF), pp. 5–6, 18–20, retrieved 2018-07-15 -- official signal specification, in russian.
  8. [8]
    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.
  9. [9]
    National Geospatial-Intelligence Agency (2005), PUB 117: Radio Navigation Aids, pp. 2–5, retrieved 2011-09-20
  10. [10]
    used to be "seconds of day" (weight 80000 - 20)
  11. [11]
    may be 1/2 (half-hour) weight of ΔUT
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