As long wave (abbreviated LW ) is called electromagnetic waves with wavelengths between 1,000 and 10,000 meters, corresponding to frequencies between 30 kHz and 300 kHz (compared to medium wave 100 m to 1 km; Shortwave 10 m to 100 m; Ultrakurzwelle 1 to 10 m ). Radio waves below 30 kHz as long waves ( VLF - Very Low Frequency ) means.
The propagation takes place as a ground wave, while the weak space waves are during the day almost completely absorbed by the D layer of the ionosphere and therefore does not return to the surface. Only when spread over the night side of the Earth remote reception is possible in coincidence of space and ground wave also interference effects ( Fading ) are then observed.
Use of the long wave
At 77.50 kHz, the time signal DCF77 of the Physikalisch -Technische Bundesanstalt is broadcast.
At 100 kHz, the radio navigation system LORAN - C operates. Furthermore, until the introduction of digital broadcasting by amplitude modulated data system GPS correction signals ( DGPS) ships, but this technique is the receiver side already largely by satellite-based systems (Satellite Based Augmentation System) replaced.
The EFR operates in Germany and Hungary, three long-wave transmitter for the radio ripple control.
For several years, amateur radio is a small long-wave range between 135.70 kHz and 137.80 kHz assigned (see LowFER ).
The transmitter sends DDH47 on the frequency 147.3 kHz, just next to the broadcasting sector. He sends weather reports, mainly for navigation, with a transmitter power of 20 kilowatts per radio teletype ( RTTY ) with 50 baud.
The commonly used for broadcasting range of the long-wave (long- wave broadcasting ) is between 148.50 and 283.50 kHz kHz. From 255 kHz and air navigation beacon is shown in the frequency usage plan of the Federal Network Agency.
The area about 283.50 kHz is used for aeronautical and marine radio.
In the long wave and the carrier frequency systems the power company work to carrier- transmission of data over power lines. These systems can interfere with the reception of radio stations in the long wave range in the vicinity of power lines considerably under certain circumstances. Previously, in some areas over the power and telephone lines, transmit radio programs with the help of carrier frequency systems. In Germany, this system was wired radio, in Switzerland this was the telephone radio.