Time and Frequency Transmission Facilities‫ڸ‬Ohtakadoya-yama LF Standard Time and Frequency Transmission Station

Disseminating accurate Japan Standard Time (JST)!
‫ ە‬Time synchronization of radio clocks‫ە‬Time standard for broadcasting and telephone time

signal services

Providing highly precise frequency standards!
‫ ە‬Frequency standard for measuring instruments‫ ە‬Frequency synchronization of radio instruments‫ڸ‬Hagane-yama LF Standard Time and Frequency Transmission Station

National Institute of Information and Communications Technology, 5DGLR5HVHDUFK,QVWLWXWH
(OHFWURPDJQHWLF6WDQGDUGV5HVHDUFK&HQWHU Space-Time Standards Laboratory Japan Standard Time 6HUYLFHGroupLow-Frequency
Standard Time andFrequency
Transmission
5IF/BUJPOBM*OTUJUVUFPG*OGPSNBUJPOBOE$PNNVOJDBUJPOT5FDIOPMPHZ /*$5 EFUFSNJOFTBOENBJOUBJOTUIFtime andfrequency standard and Japan Standard Time (JST) in
Japan as the sole organization responsible for the nationalfrequency standard. Japan Standard Time and Frequency
generated by the NICT are transmitted throughout Japan
via standard radio waves (JJY*). The master clocks ofbroadcasting stations and time signal services provided by
telephone receive JJY and synchronize with JST. Standard
radio waves transmitted by low frequency (LF) stations
contain time-coded information on time, which issuperposed on a highly precise carrier frequency signal.
5he standard time and frequency signal is synchronized
with the national standard NBJOUBJOFE CZ UIF /*$5 &WFO
UIPVHI B USBOTNJTTJPO TJHOBM JT QSFDJTF  UIF QSFDJTJPOPG SFDFJWFE TJHOBMT NBZ CF SFEVDFE CZ GBDUPST TVDI BT
DPOEJUJPOT JO UIF JPOPTQIFSF Such effects are particularly
enhanced in the HF region, causing the frequency
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
not susceptible to ionospheric conditions, are used forstandard transmissions, allowing received signals to be
used as more precise frequency standards. The precisionobtained in LF transmissions, calculated as a 24-hour
average of frequency comparison, is 1 × 10–11 (i.e., thefrequency differs from the standard frequency by
1/100,000,000,000). The Ohtakadoya-yama and Haganeyama LF Standard Time and Frequency Transmission
Stations are described on the final page. Note that
although standard signals are continuously transmitted,
they may be interrupted for the maintenance andinspection of instruments and antennas or to avoid
damage due to lightning.
For detailed information on the standard radio USBOTNJT
sion, please contact Japan Standard Time 4FSWJDF (SPVQ,Space-Time Standards -BCPSBUPSZ of NICT* JJY is the call sign of the radio station and a registered trademark(T4355749) of the NICT.

Range of LF standard time andfrequency transmission
1,500km40~50dBμV/m
1,000km50~60dBμV/m
1,500km43~53dBμV/m

500km>60dBμV/m

1,000km53~63dBμV/m

500km>53dBμV/m>63dBμV/m

Hagane-yama
LF Standard Time and Frequency
Transmission Station (60 kHz)

Ohtakadoya-yama
LF Standard Time and Frequency
Transmission Station (40 kHz)

Koganei-city, Tokyo

A numerical value below eachdistance (km) shows the value
by calculating theoreticallyassumed field strength.

1

National Institute of Information and Communications Technology

Applications of
LF Standard Time andFrequency
5ransmission

work as general quartz devices until the next reception.
The precision of time synchronization may be within several
millisecondsrelativetoJST.
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 thetime is adjusted.) They do not work properly in areas
subject to high levels of radio noise (such as inside buildings
and cars and near high-voltage power lines, electric
appliances and O.A. devices).

Radio Clock" SBEJP DMPDL BVUPNBUJDBMMZ DPSSFDUT UIF UJNF UISPVHISFDFQUJPO PG UIF TUBOEBSE UJNF BOE GSFRVFODZ USBOTNJTTJPOTJHOBM In Japan, a device synchronizes time with JST byreceiving either a 40 kHz signal from Ohtakadoya-yama LF
Standard Time and Frequency Transmission Station or a 60
kHz signal from Hagane-yama LF Standard Time andFrequency Transmission Station of the NICT.

Features of Radio-controlled Clocks
A radio-controlled clock has an automatic time-correction
function to adjust the time periodically, from once a day toonce an hour depending on the products. Radio clocks

High-Precision Frequency Calibration
The received LF standard time and frequency transmission
signal and the data released by the NICT make it possible tocalibrate the standard frequencies of radio instruments andmeasuring instruments with precision on the order of 10–11.

Observations
Standard time and frequency transmissions are used forthe time records of astronomical observations (e.g., obser
vations of meteors and occultation) and to synchronize thetime for observations made with seismometers andmeteorological instruments.

Application Fields for LF Standard Time and Frequency Transmissions
Provision of High-Precision Frequency
Standard and Japan Standard Time

Epicenter Observation
・Frequency Standard for Measuring Instrument
・Frequency Standard for Radio Station
Point
・Standard Time for Outdoor Clock (Outdoor Time Display) Depth of
Hypocenter Distance fromRadio Controlled Clocks
・Wristwatch
・Clocks
・Wall Clocks
・Outdoor Clocks

Hypocenter
Hypocenter

For Various Monitoring
Devices

LF Standard Time andFrequency TransmiVVion

・Control System for Standard timefor Seismograph and MetrologicalObservation Instruments

Home Electronics
・Computer Clock Synchronization
・Clock Synchronization for Home
Electronics
・Radio Controlled Clock Electronics

Transport andElectric Power System

Radio Controlled ClocksIRU7UDIILF

・Automatic Street Light Control System 2SHUDWLRQ・Control of Frequency and Phase
・Control Standard Time for Railway Operationsat Electric Power Stations
・Control Standard Time for Road TrafficOperations
・Control Standard Time for Taxi Clocks

National Institute of Information and Communications Technology

2Overview of
LF Standard Time andFrequency
Transmission
Facilities
5IF TUBOEBSE GSFRVFODZ BOE UJNF TJHOBM JT HFOFSBUFE CZ
IJHIQFSGPSNBODFDFTJVNBUPNJDDMPDLTPQFSBUFEJO$MPDL
3PPN 5IF TJHOBM JT UIFO BNQMJGJFE CZ B USBOTNJUUFS BOEJNQFEBODFNBUDIFE UP UIF BOUFOOB  BOE USBOTNJUUFEUISPVHIPVU+BQBO

‫ڸ‬Top of the umbrella antenna‫ڸ‬Standardtimeandfrequencytransmissionstation

The Koganei headquarters of the NICT generates,
maintains, and disseminates JST.

Block diagram ofthe signal transmission system of the standard time and frequencytransmissionstation
Communication
Satellite

NICT(koganei)
Japan Standard Time

Computer 5HPRWH0RQLWRULQJ

Status&RQWURO

1pps

Measuring
Instrument

CesiumAtRmicClock

Computer

MRQLWRULQJ
and Control
instrument

Frequency
Shift
Instrument

Umbrella
Antenna

Status/Control

Transmitter

Dummy
Load

Clock

LF Standard Time andFrequency
Transmission Facilities
Matching
Box

Lightning
ArresterTime Signal

5MHz
5MHz

Time comparison using communication
sateOlites or GPS sateOlites is adopted
reguOarly to keep and control the exact
time at LF standard time and frequency
transmission staWion.

5HPRWHFRQWURO
0RQLWRULQJLQVWUXPHQW

 5HPRWH0RQLWRULQJ
7LPH&RPSDULVRQGPS Satellite

5MHz
1pps

Transmitting
SignalGenerator

Transmitter
Transmitting Signal

Impedance
Matching Room
The LF standard time and frequency transmission stations are equipped with a private electric generator to provide backup power during power outages.

&ORFNRoom

3

Time Signal Control RoomTransmitter RoomNational Institute of Information and Communications Technology

Clock RoomTransmitter Room" DMPDL SPPN BMMPXT B IJHIQFSGPSNBODF DFTJVN BUPNJDDMPDLUPPQFSBUFTUBCMZ5IFSPPNJTDPOUSPMMFEUPNBJOUBJODFSUBJO UFNQFSBUVSF BOE IVNJEJUZ  BOE QSPWJEFT FMFDUSPNBHOFUJD TIJFMEJOH 5IFTF GFBUVSFT DPNQMFUFMZ JTPMBUF UIFBUPNJD DMPDLT GSPN DIBOHFT JO UIF TVSSPVOEJOHFOWJSPONFOUThe transmitter room has two high-power transmitter
systems (a main system and a back-up system) to amplify
the signals to 50 kW. In the case of malfunction of the
instruments in the main system or in the event of an
emergency, the back-up system automatically takes over.

Time Signal Control Room

Impedance-Matching Room

5IF -' TUBOEBSE GSFRVFODZ TJHOBM BOE UIF UJNF DPEF BSFHFOFSBUFE JO UIF UJNFTJHOBM DPOUSPM SPPN VTJOH UIFTUBOEBSE TJHOBMT PCUBJOFE XJUI UIF DFTJVN BUPNJD DMPDLT"VUPNBUJD DPOUSPM  EBUB DPMMFDUJPO  BOE JNBHFCBTFENPOJUPSJOH PG WBSJPVT JOTUSVNFOUT XJUIJO UIF TUBUJPO BSFBMTPQFSGPSNFEJOUIJTSPPN

A matching transformer is installed in the impedancematching room tomatch UIFJNQFEBODFPGthe transmitterand antenna for efficient transmission. Since high-power
radio waves pass through this room, generating a strong
electric field, the inside walls are copper-shielded and are
off-limits during transmission.

National Institute of Information and Communications Technology

4Time Codes Provided
by Standard Timeand Frequency
Transmissions
Time Codes of Standard Time andFrequency Transmissions
The time code of the LF standard time and frequency
transmission contains information on the hour, minute,day of year, year (the last two digits of the dominical year),day of week, leap second, parity for hours and minutes,
and future transmission interruptions. The time code isexpressed by a pulse train that switches the output levelsof pulse signals between 100% and 10%. The transmission
is designed for continual applicability as a frequency
standard, with there being a continuous signal even during
the low-level pulse (10%). This time code is mainly used forthe synchronization of radio clocks.

Determining and Reading the Time
Code
1 Information Contained in Time Code
5IF UJNF DPEF HJWFT UIF IPVS  NJOVUF  EBZ PG ZFBS  ZFBSUIF MBTU UXP EJHJUT PG UIF EPNJOJDBM ZFBS  EBZ PG XFFL 
MFBQ TFDPOE  QBSJUZ CJUT GPS IPVST BOE NJOVUFT  BOEOPUJGJDBUJPOPGGVUVSFUSBOTNJTTJPOJOUFSSVQUJPOT
5IF IPVS  NJOVUF  EBZ PG ZFBS  ZFBS  BOE EBZ PG XFFL BSFSFQSFTFOUFE JO CJOBSZ UFSNT <#$% #JOBSZ $PEFE %FDJNBM/PUBUJPO QPTJUJWFMPHJD>

2 Second Signal
The start of each second corresponds to the rising of theleading edge of the pulse signal. The point at which thepulse reaches 55% of its full amplitude (midpoint between
10% and 100% amplitude) is synchronous with the second
signal of standard time.

3 Pulse Width
Marker (M) and position markers (P0–P5) : 0.2 s ± 5 ms
Binary 0 : 0.8 s ± 5 ms
Binary 1 : 0.5 s ± 5 ms

4 Output Interval
A code with a period of 60 seconds (60 bits) is transmitted
every second.

5 Standard Time of Time CodeThe time (year, annual date, hour, and minute) of the firstmarker (M) in each period is encoded and transmitted.

6 Marker (M) Position
The marker (M) corresponds to the exact minute (the zerosecond of each minute).

7 Positions of the Position Markers (P0–P5)

The Year 2100 Problem
Since the time code must represent a great deal of information in alimited number of bits, only the last two digits of the dominical year
are used to indicate the year and the day is presented only as anannual date. The year of 2100 is not a leap year (since it is indivisible by400). Radio clocks for which a leap year is set every four years will falsely recognize
the year 2100 as a leap year and will display February 29. In the case that thestandard transmission is to be used for 100 years or more, radio clocks produced

5IFQPTJUJPONBSLFS1OPSNBMMZDPSSFTQPOETUPUIFSJTFPG
UIF UI TFDPOE GPS OPOMFBQ TFDPOET  )PXFWFS  GPS B
QPTJUJWF MFBQ TFDPOE JOTFSUJPO PG B TFDPOE  1
DPSSFTQPOETUPUIFSJTFPGUIFUITFDPOE JOUIJTDBTF UIF
UI TFDPOE JT SFQSFTFOUFE CZ B CJOBSZ   'PS B OFHBUJWF
MFBQ TFDPOE SFNPWBM PG B TFDPOE  1 DPSSFTQPOET UP UIFSJTFPGUIFUITFDPOE1PTJUJPONBSLFST1 1 1 1BOE
1DPSSFTQPOEUPUIFSJTFPGUIFUI UI UI UI BOE
UITFDPOET SFTQFDUJWFMZ

since 2000 have been programmed to recognize the year 00 as a nonleap year.

5

National Institute of Information and Communications Technology

Representation of Information(a) Hour (six bits: 20h, 10h, 8h, 4h, 2h, 1h)
The hour in Japan Standard Time (JST) in 24-hour
representation(b) Minute (seven bits: 40m, 20m, 10m, 8m, 4m, 2m, 1m)
The JST minute(c) Annual date (ten bits: 200d, 100d, 80d, 40d, 20d, 10d, 8d,
4d, 2d, 1d)
The day of the year, counting January 1 as day 1. Thus,
December 31 is expressed as 365 in a non-leap year andas 366 in a leap year.
(d) Year (eight bits: 80y, 40y, 20y, 10y, 8y, 4y, 2y, 1y)
The last 2 digits of the dominical year(e) Day of the week (three bits: 4w, 2w, 1w)
Values 0–6 allocated to Sunday–Saturday.
( f ) Leap second information (two bits: LS1, LS2)
The leap-second adjustment is performed immediately
before 9:00 (Japan Standard Time) on the first day of themonth in question. Leap-second information iscontinuously transmitted from 9:00 on the second dayof the previous month to 8:59 on the first day of therelevant month.

Mark of 0.8 sec = 0 in binary

parity(h) Spare bits (two bits: SU1, SU2)
Spare bits are reserved for additions of items to becontained within the time code (such as daylightsavingstime).
To date, these bits have had a value of zero.
( i ) Notification of transmission interruption (six bits: ST1,
ST2, ST3, ST4, ST5, ST6)
When interruptions of standard time and frequency
transmission are scheduled (e.g., for maintenance andinspection) advance notice is given using notification
bits. When there are no plans for interruption, all spare
bits have values of zero.
*Detailed definition on each bit is given at
IUUQTKKZOJDUHPKQKKZUSBOTJOEFYIUNM

Mark of 0.5 sec = 1 in binary

Mark of 0.2 sec = position(Pn),reference marker(M)hourannual dateminuteannual date(g) Parity (two bits: PA1, PA2)
Parity bits are signals used to determine whether thehour and minute signals are correctly read. PA1 and PA2correspond respectively to the hour and minute. Each is
one bit representing even parity.
PA1 = (20 h + 10 h + 8 h + 4 h + 2 h + 1 h) mod 2
PA2 = (40 m + 20 m + 10 m + 8 m + 4 m + 2 m + 1 m)
mod 2(mod 2 represents the remainder of division by 2)

spare
bit

time code when call sign transmits(every 15 minutes and 45 minutes)
the same as above from 0 sec to 40 sec

year (last 2 digitsof the dominical year)

week

The time codecommunicates the time of
the reference marker
position for 60 seconds.
For example,left figure
shows JunH 10(annual day:162), 2016,
Friday, 17:15 (ThereLVQROHDSVHFRQGZLWKLQRQHPRQWK 

leap second

call sign
Morse sign
Notification of starting to Notification of the periodinterrupt transmission to interrupt transmission

National Institute of Information and Communications Technology

6Descriptions of the LF Standard Time andFrequency Transmission Facilities
Ohtakadoya-yama LF Standard Timeand Frequency Transmission Station

Hagane-yama LF Standard Time andFrequency Transmission Station

1. Location

1. Location

Near the summit of Mt. Ohtakadoya on the border between
Miyakoji, Tamura City and Kawauchi Village in Futaba
County of Fukushima Prefecture

Near the summit of Mt. Hagane on the border between Fuji,
Saga City of Saga Prefecture and Itoshima City of Fukuoka
Prefecture

Elevation
LatitudeLongitude

Elevation
LatitudeLongitude: approximately 790 m: 37° 22’ 21” N: 140° 50’ 56” E

2. Specifications of the Transmission Station
Name of the Station:
Ohtakadoya-yama LF Standard Time and Frequency
Transmission Station, National Institute of Information
and Communications Technology (NICT)
Antenna Power: 50 kW(antenna efficiency: approx. 25%)
Radio Wave Mode: A1B
Carrier frequency: 40 kHz
Total area of station: approx. 88,668 m2
Antenna facility:
Umbrella antenna, 250 m above ground
Operation:$ontinuous operation (except during maintenance andinspection of instruments and in the event of possible
lightning): approximately 900 m: 33° 27’ 56” N: 130° 10’ 32” E

2. Specifications of the Transmission Station
Name of the Station:
Hagane-yama LF Standard Time and Frequency
Transmission Station, National Institute of Information
and Communications Technology (NICT)
Antenna Power: 50 kW(antenna efficiency: approx. 45%)
Radio Wave Mode: A1B
Carrier frequency: 60 kHz
Total area of station: approx. 115,803 m2
Antenna facility:
Umbrella antenna, 200 m above ground
Operation:
Continuous operation (except during maintenance andinspection of instruments and in the event of possible
lightning)

Fukuoka Prefecture
Fukushima Prefecture

Ohtakadoya-yama LF Standard Timeand Frequency Transmission Station
Miyakoji, Tamura City
Kawauchi Village, Futaba County

Hagane-yama LF Standard Timeand Frequency Transmission Station
Fuji, Saga City, Saga Prefecture
Itoshima City, Fukuoka Prefecture

Fukushima City

Kitakyushu City

Fukuoka City
Itoshima City

Tamura City
Koriyama City
Tomioka Town

Imari City

Saga City
Kurume City

Iwaki City

Saga Prefecture

National Institute of Information and Communications Technology
3BEJP3FTFBSDI*OTUJUVUF &MFDUSPNBHOFUJD4UBOEBSET3FTFBSDI$FOUFS
Space-Time Standards Laboratory, Japan Standard Time 4FSWJDFGroup
4-2-1 Nukui-Kitamachi, Koganei, Tokyo 184-8795 Japan
Tel: +81-42-327-6985 Fax: +81-42-327-6689 URL: httpT://jjy.nict.go.jp E-mail: horonet@NMnict.go.jp
This CSPDIVSFJTQSJOUFEPOSFDZDMFEQBQFS

The 1st editJPO: OctPCFS2004
Revised: "QSJM