HBG (time signal)

HBG is a low frequency time signal transmitter for the Swiss time reference system. It currently operates on 75 kHz with 20 kW and is located in Prangins, Switzerland. Due to aging antennas the Swiss Federal Government has decided to shut down HBG on 31 December 2011. The transmissions have endet on the 1st. of January 2012. The signal is no longer present.

At the beginning of each second (with the exception of the 59th), the carrier signal is interrupted for a period of 0.1 s or 0.2 s, which corresponds to a binary "0" or "1". The transmission of the minute, hour, calendar date, day of the week, month and current year is achieved by means of a BCD code identical to that of DCF77.

Like DCF77, the carrier is not interrupted during the last second of each minute.

Differences from the DCF77 time code:

• The carrier frequency.
• Phase modulation is not included.
• Amplitude modulation is done by disabling the transmitter (0% power) rather than reducing it to 15% power as DCF77 does.
• Announcement bits warning of impending time zone changes or leap seconds are sent 12 hours in advance, rather than 1 hour.
• The first pulse of each minute is not a standard 0 bit as DCF77 sends. Instead, it is a double pulse, two 0.1 s interruptions separated by 0.1 s of carrier. A triple pulse signals the start of a new hour, and a four-pulse signal is transmitted at noon and midnight.

External links

• Information page on Swiss federal office of metrology (METAS)
• Pictures of the HBG transmitter in Prangins, Switzerland (emetteurs.ch)
• Observation of HBG during a leap second
• (German) Description of the HBG time code.
• (German) Press release concerning the cessation of the time dissemination transmitter HBG at Prangins on 31 December 2011 ( (English) translation)