DCF77

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DCF77

DCF77 is a longwave

Mainflingen longwave transmitter

Mainflingen longwave transmitter is a large facility for commercial longwave transmissions at Mainflingen, Hesse, Germany. It uses several T- and triangle antennas, which are mounted on guyed masts of lattice steel, insulated against ground....
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....
and standard-frequency radio station. Its primary and backup transmitter

Transmitter

For biologic transmitters, see transmitter substance.A transmitter is an Electronics machine which, usually with the aid of an antenna , propagates an electromagnetic radiation Signalling such as radio, television, or other telecommunications....
are located in Mainflingen

Mainflingen

Mainflingen is a small settlement of about 3800 inhabitants, a constituent community of the municipality Mainhausen in Hesse, Germany.It is rather well-known for being the site of the Mainflingen longwave transmitter which broadcasts the official standard time as given by the atomic clocks of the PTB Braunschweig....
, about 25 km south-east of Frankfurt

Frankfurt

is the largest city in the German States of Germany of Hesse and the List of cities in Germany with more than 100,000 inhabitants in Germany, with a 2008 population of 670,000....
, Germany

Germany

Germany , officially the Federal Republic of Germany , is a country in Central Europe. It is bordered to the north by the North Sea, Denmark, and the Baltic Sea; to the east by Poland and the Czech Republic; to the south by Austria and Switzerland; and to the west by France, Luxembourg, Belgium, and the Netherlands....
. It is operated by Media Broadcast GmbH (previously a subsidiary of Deutsche Telekom AG), on behalf of the Physikalisch-Technische Bundesanstalt

Physikalisch-Technische Bundesanstalt

The Physikalisch-Technische Bundesanstalt is based in Braunschweig and Berlin. It is the national institute for natural and engineering sciences and the highest technical authority for metrology and physical safety engineering in Germany....
, Germany's national physics

Physics

Physics is the natural science which examines basic concepts such as energy, force, and spacetime and all that derives from these, such as mass, charge, matter and its Motion ....
laboratory.

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Encyclopedia

DCF77 is a longwave

Mainflingen longwave transmitter

Time signal

A time signal is a visible, audible, mechanical, or electronic signal used as a reference to determine the time of day....
and standard-frequency radio station. Its primary and backup transmitter

Transmitter

Mainflingen

Frankfurt

is the largest city in the German States of Germany of Hesse and the List of cities in Germany with more than 100,000 inhabitants in Germany, with a 2008 population of 670,000....
, Germany

Germany

Physikalisch-Technische Bundesanstalt

Physics

Physics is the natural science which examines basic concepts such as energy, force, and spacetime and all that derives from these, such as mass, charge, matter and its Motion ....
laboratory. DCF77 has been in service as a standard-frequency station since 1959; date and time information was added in 1973.

The 77.5 kHz carrier signal is generated from local atomic clock

Atomic clock

An atomic clock is a type of clock that uses an atomic resonance frequency standard as its timekeeping element. They are the most accurate time and frequency standards known, and are used as primary standards for international Time dissemination, and to control the frequency of television broadcasts and GPS satellite signals....
s that are linked with the German master clocks in Braunschweig

Braunschweig

Braunschweig , known as Brunswiek in Low German, is a city of 245,810 people , located in Lower Saxony, Germany. It is located north of the Harz mountains at the farthest navigable point of the Oker river, which connects to the North Sea via the rivers Aller and Weser....
. With a relatively-high power of 50 kW, the station can be received in large parts of Europe, as far as 2000 km from Frankfurt (and further away depending on signal propagation

Radio propagation

Radio propagation is a term used to explain how radio waves behave when they are transmitted, or are wave propagation from one point on the Earth to another....
and local interference. Good reception is possible in Portugal during night hours, for example). Its signal carries an amplitude-modulated, pulse-width coded 1 bit/s data signal. The same data signal is also phase modulated onto the carrier

Carrier wave

In telecommunications, a carrier wave, or carrier is a waveform that is Modulation with an signal for the purpose of conveying information....
using a 511-bit long pseudorandom sequence (direct-sequence spread spectrum

Direct-sequence spread spectrum

In telecommunications, direct-sequence spread spectrum is a modulation technique. As with other spread spectrum technologies, the transmitted signal takes up more Bandwidth than the information signal that is being modulated....
modulation). The transmitted data repeats each minute

the current date and time;
a leap second
Leap second

A leap second is a plus or minus one-second adjustment to the Coordinated Universal Time time scale that keeps it close to Solar time. UTC, which is used as the basis for official time-of-day radio broadcasts for civil time, is maintained using extremely precise atomic clocks....
warning bit;
a summer time
European Summer Time

European Summer Time is the arrangement in Europe by which clocks are advanced by one hour in Spring to make the most of seasonal daylight. This is done in all of the countries of Europe except Iceland which observes Greenwich Mean Time all year round....
bit;
a primary/backup transmitter identification bit;
several parity bit
Parity bit

A parity bit is a bit that is added to ensure that the number of bits with value of 1 in a given set of bits is always even number or odd number....
s.

Since 2003, 14 previously unused bits of the time code have been used for civil defence emergency signals. This is still an experimental service, aimed to replace one day the German network of civil defense siren

Civil defense siren

A civil defense siren is a Machine or electronic device for generating sound to provide warning of approaching danger and sometimes to indicate when the danger has passed....
s.

The callsign DCF77 stands for D=Deutschland (Germany), C=long wave signal, F=Frankfurt, 77=frequency: 77.5 kHz.

Radio clock

Radio clock

A radio clock is a clock that is synchronized by a time code bit stream transmitted by a radio transmitter connected to a time standard such as an atomic clock....
s and watch

Watch

A watch is a timepiece that is made to be worn on a person. The term now usually refers to a wristwatch, which is worn on the wrist with a strap or bracelet....
es have been very popular in Europe since the late 1980s and most of them use the DCF77 signal to set their time automatically.

DCF77

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