RBU is a time signal radio station located in Moscow (). It transmits a continuous 10 kW time code on 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.Some info and imagery from around 2005–20010 can be found in these forum pages:
This LiveJournal post has photos of buildings' internals and equipment (from 2014, long after the object was abandoned): In 2008, it has been transferred to the Taldom transmitter at ; the antennas at Kupavna have been demolished around mid-January 2010.
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.
Time code Every 100 ms, synchronized to the UTC second, one bit is transmitted: + RBU tenth second format. Note that there is a modulation type error in this reference. -- official signal specification, in russian. Start Duration Signal +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:
+ RBU second format Start Significance 0 ms Time code data bit 1 100 ms Time code data bit 2 200 ms Always 0 (100 Hz tone) 300 ms 400 ms 500 ms 600 ms 700 ms Always 0, except 1 before start of minute.Minute marker 800 ms 900 ms Always 1 (312.5 Hz tone). Second marker
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.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 Hz.
+ RBU time codeShaded bits are fixed Second Data bit 1 Data bit 2 Second Data bit 1 Data bit 2 Weight Meaning Weight Meaning Weight Meaning Weight Meaning 00 1 Always 1 1 Always 1 30 4 Year(00–99) 8 Truncated MJD(0000–9999) 01 0 Unused, zero +0.1 DUT1(+0.1–+0.8 s)Unary encoding,bit set ifDUT1 ≥ Weight 31 2 4 02 0 +0.2 32 1 2 03 0.02 dUT1(±0.02–±0.08 s)Bit set ifmod(dUT1) ≥ Weight +0.3 33 10 Month(01–12) 1 04 0.04 +0.4 34 8 0 Unused, zeroused to be "seconds of day" (weight 80000 - 20) 05 0.06 +0.5 35 4 0 06 0.08 +0.6 36 2 0 07 ± +0.7 37 1 0 08 0 Unused, zero +0.8 38 4 Day of week1=Monday7=Sunday 0 09 0 −0.1 DUT1(−0.1–−0.8 s)Unary encoding,bit set ifDUT1 ≤ Weight 39 2 0 10 0 −0.2 40 1 0 11 0.02 dUT1(±0.02–±0.08 s)Bit set ifmod(dUT1) ≥ Weight −0.3 41 20 Day of month(1–31) 0 12 0.04 −0.4 42 10 0 13 0.06 −0.5 43 8 0 14 0.08 −0.6 44 4 0 15 ± −0.7 45 2 0 16 0 Unused, zero −0.8 46 1 0 17 0 0 Unused, zero 47 20 Hour(00–23) 0 18 ± ΔUTMoscow timeminus UTCFixed +3 since26 Oct 2014 8000 TruncatedJulian Day(0000–9999)Last 4 digits ofModified Julianday number 48 10 0 19 10 4000 49 8 P1 TJD bits 18–25 Evenparityover 20 8 2000 50 4 P2 TJD bits 26–33 21 4 1000 51 2 0 Unused, zero 22 2 800 52 1 0 23 1 400 53 40 Minute(00–59) P3 ΔUT bits 18–24 24 0may be (half-hour) weight of ΔUT Unused, zero 200 54 20 P4 Year bits 25–32 25 80 Year(00–99) 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 29 8 10 59 1 0 Unused, zero 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