Time and Frequency Transmission Facilities Ohtakadoya-yama LF Standard Time and Frequency Transmission Stationڸ Disseminating accurate Japan Standard Time (JST)! Time synchronization of radio clocks ە Time standard for broadcasting and telephone timeە signal services Providing highly precise frequency standards! Frequency standard for measuring instruments ە Frequency synchronization of radio instruments ە Hagane-yama LF Standard Time and Frequency Transmission Stationڸ National Institute of Information and Communications Technology, 5DGLR5HVHDUFK,QVWLWXWH (OHFWURPDJQHWLF6WDQGDUGV5HVHDUFK&HQWHU Space-Time Standards Laboratory Japan Standard Time 6HUYLFHGroup PG SFDFJWFE TJHOBMT NBZ CF SFEVDFE CZ GBDUPST TVDI BT Low-Frequency DPOEJUJPOTJOUIFJPOPTQIFSFSuch effects are particularly enhanced in the HF region, causing the frequency Standard Time and precision of the received wave to deteriorate to nearly 1 × 10–8 (i.e., the frequency differs from the standard frequency by 1/100,000,000). Therefore, low frequencies, which are Frequency not susceptible to ionospheric conditions, are used for standard transmissions, allowing received signals to be Transmission used as more precise frequency standards. The precision obtained in LF transmissions, calculated as a 24-hour average of frequency comparison, is 1 × 10–11 (i.e., the 5IF/BUJPOBM*OTUJUVUFPG*OGPSNBUJPOBOE$PNNVOJDBUJPOT frequency differs from the standard frequency by 5FDIOPMPHZ /*$5 EFUFSNJOFTBOENBJOUBJOTUIFtime and 1/100,000,000,000). The Ohtakadoya-yama and Hagane- frequency standard and Japan Standard Time (JST) in yama LF Standard Time and Frequency Transmission Japan as the sole organization responsible for the national Stations are described on the final page. Note that frequency standard. Japan Standard Time and Frequency although standard signals are continuously transmitted, generated by the NICT are transmitted throughout Japan they may be interrupted for the maintenance and via standard radio waves (JJY*). The master clocks of inspection of instruments and antennas or to avoid broadcasting stations and time signal services provided by damage due to lightning. telephone receive JJY and synchronize with JST. Standard radio waves transmitted by low frequency (LF) stations For detailed information on the standard radio USBOTNJT contain time-coded information on time, which is sion, please contact Japan Standard Time 4FSWJDF (SPVQ, superposed on a highly precise carrier frequency signal. Space-Time Standards -BCPSBUPSZ of NICT 5he standard time and frequency signal is synchronized * JJY is the call sign of the radio station and a registered trademark with the national standard NBJOUBJOFE CZUIF/*$5&WFO (T4355749) of the NICT. UIPVHI B USBOTNJTTJPO TJHOBM JT QSFDJTF UIF QSFDJTJPO Range of LF standard time and frequency transmission 1,500km 40~50dBμV/m 1,000km 50~60dBμV/m 1,500km 43~53dBμV/m 500km >60dBμV/m 1,000km 500km 53~63dBμV/m >63dB>53dBμV/m Ohtakadoya-yama LF Standard Time and Frequency Transmission Station (40 kHz) Hagane-yama LF Standard Time and Frequency Koganei-city, Tokyo Transmission Station (60 kHz) A numerical value below each distance (km) shows the value by calculating theoretically assumed field strength. 1 National Institute of Information and Communications Technology work as general quartz devices until the next reception. Applications of The precision of time synchronization may be within several millisecondsrelativetoJST. LF Standard Time and Radio-controlled clocks need to be placed where standard waves are easily received to ensure the adjustment of time. (It takes several minutes to receive the signal before the Frequency time is adjusted.) They do not work properly in areas subject to high levels of radio noise (such as inside buildings 5ransmiss ion and cars and near high-voltage power lines, electric appliances and O.A. devices). Radio Clock High-Precision Frequency Calibration " SBEJP DMPDL BVUPNBUJDBMMZ DPSSFDUT UIF UJNF UISPVHI SFDFQUJPO PG UIF TUBOEBSE UJNF BOE GSFRVFODZ USBOTNJTTJPO The received LF standard time and frequency transmission TJHOBM In Japan, a device synchronizes time with JST by signal and the data released by the NICT make it possible to receiving either a 40 kHz signal from Ohtakadoya-yama LF calibrate the standard frequencies of radio instruments and Standard Time and Frequency Transmission Station or a 60 measuring instruments with precision on the order of 10–11. kHz signal from Hagane-yama LF Standard Time and Frequency Transmission Station of the NICT. Observations Features of Radio-controlled Clocks Standard time and frequency transmissions are used for the time records of astronomical observations (e.g., obser A radio-controlled clock has an automatic time-correction vations of meteors and occultation) and to synchronize the function to adjust the time periodically, from once a day to time for observations made with seismometers and once an hour depending on the products. Radio clocks meteorological instruments. Application Fields for LF Standard Time and Frequency Transmissions Provision of High-Precision Frequency Standard and Japan Standard Time Epicenter ・Frequency Standard for Measuring Instrument Observation ・Frequency Standard for Radio Station Point ・Standard Time for Outdoor Clock (Outdoor Time Display) Depth of Hypocenter Hypocenter Distance from Hypocenter Hypocenter Hypocenter Radio Controlled Clocks ・Wristwatch ・Clocks ・Wall Clocks For Various Monitoring ・Outdoor Clocks Devices ・Control System for Standard time LF Standard Time and for Seismograph and Metrological Observation Instruments Frequency TransmiVVion Home Electronics ・Computer Clock Synchronization ・Clock Synchronization for Home Electronics ・Radio Controlled Clock Electronics Transport and Electric Power System Radio Controlled ClocksIRU7UDIILF ・Automatic Street Light Control System 2SHUDWLRQ ・Control of Frequency and Phase ・Control Standard Time for Railway Operations at Electric Power Stations ・Control Standard Time for Road TrafficOperations ・Control Standard Time for Taxi Clocks National Institute of Information and Communications Technology 2 Overview of LF Sta ndard Time and Fre quency Transmission Facilities 5IF TUBOEBSE GSFRVFODZ BOE UJNF TJHOBM JT HFOFSBUFE CZ IJHIQFSGPSNBODFDFTJVNBUPNJDDMPDLTPQFSBUFEJO$MPDL 3PPN 5IF TJHOBM JT UIFO BNQMJGJFE CZ B USBOTNJUUFS BOE JNQFEBODFNBUDIFE UP UIF BOUFOOB BOE USBOTNJUUFE UISPVHIPVU+BQBO Top of the umbrella antennaڸ Standardtimeandfrequencytransmissionstationڸ The Koganei headquarters of the NICT generates, maintains, and disseminates JST. Block diagram ofthe signal transmission system of the standard time and frequency transmission station Communication GPS Satellite Satellite NICT(koganei) Time comparison using communication sateOlites or GPS sateOlites is adopted 5HPRWHFRQWURO reguOarly to keep and control the exact Japan Standard Time Computer 0RQLWRULQJLQVWUXPHQW time at LF standard time and frequency transmission staWion. 5HPRWH0RQLWRULQJ 5HPRWH0RQLWRULQJ Umbrella 7LPH&RPSDULVRQ Antenna Status&RQWURO Status/Control LF Standard Time and Measuring MRQLWRULQJ Frequency Instrument Computer and Control Transmitter 1pps instrument Transmission Facilities Cesium AtRmic Dummy Matching Lightning Clock Clock Load Box Arrester 5MHz Time Signal 5MHz Frequency 5MHz Transmitting Shift Signal Transmitter Instrument 1pps Generator Transmitting Signal &ORFNRoom Impedance Time Signal Control Room Transmitter Room Matching Room The LF standard time and frequency transmission stations are equipped with a private electric generator to provide backup power during power outages. 3 National Institute of Information and Communications Technology Clock Room Transmitter Room " DMPDL SPPN BMMPXT B IJHIQFSGPSNBODF DFTJVN BUPNJD The transmitter room has two high-power transmitter DMPDLUPPQFSBUFTUBCMZ5IFSPPNJTDPOUSPMMFEUPNBJOUBJO systems (a main system and a back-up system) to amplify DFSUBJO UFNQFSBUVSF BOE IVNJEJUZ BOE QSPWJEFT FMFDUSP the signals to 50 kW. In the case of malfunction of the NBHOFUJDTIJFMEJOH5IFTFGFBUVSFTDPNQMFUFMZJTPMBUFUIF instruments in the main system or in the event of an BUPNJD DMPDLT GSPN DIBOHFT JO UIF TVSSPVOEJOH emergency, the back-up system automatically takes over. FOWJSPONFOU Time Signal Control Room Impedance-Matching Room 5IF -' TUBOEBSE GSFRVFODZ TJHOBM BOE UIF UJNF DPEF BSF A matching transformer is installed in the impedance- HFOFSBUFE JO UIF UJNFTJHOBM DPOUSPM SPPN VTJOH UIF matching room tomatch UIFJNQFEBODFPGthe transmitter TUBOEBSE TJHOBMT PCUBJOFE XJUI UIF DFTJVN BUPNJD DMPDLT and antenna for efficient transmission. Since high-power "VUPNBUJD DPOUSPM EBUB DPMMFDUJPO BOE JNBHFCBTFE radio waves pass through this room, generating a strong NPOJUPSJOH PG WBSJPVT JOTUSVNFOUT XJUIJO UIF TUBUJPO BSF electric field, the inside walls are copper-shielded and are BMTPQFSGPSNFEJOUIJTSPPN off-limits during transmission. National Institute of Information and Communications Technology 4 Time Codes Provi ded Determining and Reading the Time by Standard Time Code 1 Information Contained in Time Code 5IF UJNF DPEF HJWFT UIF IPVS NJOVUF EBZ PG ZFBS ZFBS and Frequency UIF MBTU UXP EJHJUT PG UIF EPNJOJDBM ZFBS EBZ PG XFFL MFBQ TFDPOE QBSJUZ CJUT GPS IPVST BOE NJOVUFT BOE Transmissions OPUJGJDBUJPOPGGVUVSFUSBOTNJTTJPOJOUFSSVQUJPOT 5IFIPVS NJOVUF EBZPGZFBS ZFBS BOEEBZPGXFFLBSF SFQSFTFOUFEJOCJOBSZUFSNT<#$% #JOBSZ$PEFE%FDJNBM Time Codes of Standard Time and /PUBUJPO QPTJUJWFMPHJD> Frequency Transmissions 2 Second Signal The time code of the LF standard time and frequency The start of each