HBG (time signal transmitter)

HBG

Basic data

Place:

Prangins

Canton:

Vaud

Country:

Switzerland

Altitude :

418 m

Coordinates: 46 ° 24 '30.2 " N , 6 ° 15' 10.1" E ; CH1903: 508819 / 140362

Use:

Time signal transmitter

Demolition :

September 6, 2012

Data on the transmission system

Number of towers / masts:

2

Construction time:

1928

Operating time:

1966-2011

Waveband :

LW transmitter

Position map

HBG

Transmission from HBG

The time signal transmitter HBG was a time transmission service of the Federal Office of Metrology (METAS) in Switzerland .

signal

This long wave transmitter on Lake Geneva beamed the legal Swiss time ( Central European Time CET or Central European Summer Time CEST) and became the synchronization of radio clocks used. The name HBG is the station's callsign .

The format (HBG code) of the time signals broadcast has been compatible with the German time signal transmitter DCF77 since January 1, 2001 . Previously there were minor differences like the 59 second. The commercially available receiver modules were mostly able to decode both the old and the new code.

HBG broadcast 24 hours a day. The broadcast time signals could be used without restriction and free of charge.

Channel

The transmitter was put into operation in 1966 in Prangins on Lake Geneva . The carrier frequency was 75 kHz ( long wave ) and was emitted with a transmission power of 25 kW via an omnidirectional antenna.

An L-antenna , which was stretched between two free-standing steel lattice towers, each 125 m high, was used as the antenna system. Both towers were grounded and had a floor area of 10 × 10 meters. The range of the bump was around 500 km and covered the whole of Switzerland and parts of neighboring countries. A perfect reception was guaranteed in this area, also inside buildings and mostly even in the basement. In the range from 500 km to 1000 km, reception could be impaired by interference with the sky wave ( fading ), from 1000 km the sky wave then predominated.

The transmitter was operated first by PTT , then until May 2000 by Swisscom and most recently by the Federal Office of Metrology (METAS). In August 2009 it was announced that the station would cease operations at the end of 2011. The antenna masts showed signs of aging, which represented a safety risk and which could only have been removed with considerable effort. The two transmission masts were demolished by a controlled demolition on September 6, 2012 at 2:00 p.m. local time.

Time and frequency

The Federal Office of Metrology (METAS) has the legal task of providing the basic units of measurement , including the second in accordance with the International System of Units SI. For this purpose, the Laboratory for Time and Frequency of the Federal Office operates several atomic clocks that serve as frequency and time standards . The statutory Swiss time is also calculated from these atomic clocks.

The HBG transmitter transmitted not only the Swiss time, but also a very precise frequency: The carrier frequency of the transmitter was also derived from these atomic clocks and could therefore be kept within 2 · 10 ⁻¹² at 75 kHz and was therefore a calibration frequency .

Format of the time signals

Transferred information
second	Coded information
0	Reserve (not defined)
1 to 14	Weather information from MeteoTime
15th	Reserve (not defined)
16	Advance notice of change of zone time CET / CEST
17/18	0/1 = CET, 1/0 = CEST
19th	Leap second advance notice
20th	Start bit, always 1
21 to 27	minute
28	Parity bit for bits 16 through 27
29 to 34	hour
35	Parity bit for bits 29 through 34
36 to 41	Day of month
42 to 44	weekday
45 to 49	month
50 to 57	year
58	Parity bit for bits 36 to 57

At the beginning of every second the carrier signal was briefly interrupted ( amplitude shift keying ). This second pulse was absent in the last second of every minute (i.e. in second 59) to signal the beginning of a new minute. For this purpose, a double pulse was sent in the first second of the new minute (second 0). A triple pulse instead of a double pulse marked the beginning of a new hour, a quadruple pulse the beginning of a new day.

At irregular intervals needed to leap second are inserted to the Coordinated Universal Time UTC back to (of the Earth's rotation-dependent) world time UT1 equalize. In these cases the minute concerned was 61 seconds long, the leap second was added at the end (as 60 second) and also did not receive a second pulse.

Additional information on the date and time was coded in the second pulses: Short seconds pulses of 100 ms duration meant a binary 0, longer seconds pulses of 200 ms duration meant a binary 1 ( pulse width modulation ). In this way, 59 bits of information could be transmitted every minute. The exact structure of this minute data telegram is contained in the adjacent table.

The information transmitted can be divided into several classes:

Advance notice : These bits were set 12 hours before the event (i.e. inserting a leap second or changing the zone time between CET and CEST) and deleted again immediately after the event.
Numbers : In BCD format , sent with the least significant bit first ( little endian format ). The bits received with the valences 1, 2, 4, 8, 10, 20, 40, 80. Only as many bits were planned for each number as the value range required, for example 7 bits for the minute (range 0 to 59), but only 6 bits for the hour (range 0 to 23).
Weekday : The received number was interpreted according to ISO 8601 : 1 = Monday, 2 = Tuesday to 7 = Sunday
Parity bits : The parity bits added the sum of the specified data bits to an even number ( even parity ) and were used for error detection .