HBG is a low frequency

Low frequency

Low frequency or low freq or LF refers to radio frequencies in the range of 30 kHz–300 kHz. In Europe, and parts of Northern Africa and of Asia, part of the LF spectrum is used for AM broadcasting as the longwave band. In the western hemisphere, its main use is for aircraft beacon,...

 time signal

Time signal

A time signal is a visible, audible, mechanical, or electronic signal used as a reference to determine the time of day.-Audible and visible time signals:...

 transmitter

Transmitter

In electronics and telecommunications a transmitter or radio transmitter is an electronic device which, with the aid of an antenna, produces radio waves. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating...

 for the Swiss time reference system. It currently operates on 75 kHz with 20 kW and is located in Prangins

Prangins

Prangins is a municipality in the district of Nyon in the canton of Vaud in Switzerland. It is located on Lake Geneva.-Geography:Prangins has an area, , of . Of this area, or 54.7% is used for agricultural purposes, while or 13.1% is forested...

, Switzerland. Due to aging antennas the Swiss Federal Government has decided to shut down HBG on 31 December 2011.

At the beginning of each second (with the exception of the 59th), the carrier

Carrier wave

In telecommunications, a carrier wave or carrier is a waveform that is modulated with an input signal for the purpose of conveying information. This carrier wave is usually a much higher frequency than the input signal...

 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

DCF77

DCF77 is a longwave time signal and standard-frequency radio station. Its primary and backup transmitter are located in Mainflingen, about 25 km south-east of Frankfurt am Main, Germany. It is operated by Media Broadcast GmbH , on behalf of the Physikalisch-Technische Bundesanstalt, Germany's...

.

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 Description of the HBG time code. Press release concerning the cessation of the time dissemination transmitter HBG at Prangins on 31 December 2011 ( translation)