As long wave (LW) refers to electromagnetic waves with wavelengths of 1000 to 10,000 meters accordingly, frequencies between 30 kHz and 300 kHz (compared to the center shaft 100 m to 1 km; short wave 10 to 100 m; Ultrakurzwelle 1 to 10 m). Radio waves below 30 kHz are referred to as longest waves (VLF - Very Low Frequency).
The propagation takes place as a ground wave , while the weakly pronounced sky wave is almost completely absorbed by the D-layer of the ionosphere during the day and therefore does not return to the earth's surface. Long-range reception is only possible if the earth's night side spreads, and interference phenomena ( fading ) can also be observed when the space and ground waves meet .
Use of the long wave
The time signal DCF77 of the Physikalisch-Technische Bundesanstalt is broadcast on 77.50 kHz .
The radio navigation system LORAN-C works at 100 kHz . Until the introduction of digital broadcasting, GPS correction signals ( DGPS ) will be sent via an amplitude-modulated data system , but this technology has already been largely replaced by satellite-based augmentation systems on the receiver side .
EFR GmbH operates three long-wave transmitters for radio ripple control in Germany and Hungary .
For some years now, amateur radio has also been assigned a small long-wave range between 135.70 kHz and 137.80 kHz (see LowFER ).
The DDH47 transmitter broadcasts on the frequency 147.3 kHz, just next to the broadcast area. It sends weather reports, mainly for seafaring, with a transmission power of 20 kilowatts by radio telex (RTTY) at 50 baud .
The long wave range usually used for radio transmissions ( long wave radio ) is between 148.50 and 283.50 kHz. From 255 kHz, the frequency plan of the Federal Network Agency also shows flight navigation radio beacons .
The range above 283.50 kHz is used for aeronautical and marine radio .
In the long-wave range, the carrier frequency systems of the energy supply companies also work for the carrier-frequency transmission of measurement data via high-voltage lines . Under certain circumstances, these systems can considerably interfere with the reception of radio transmitters in the long-wave range near power lines . In the past , radio programs were transmitted in some areas via power and telephone lines , also with the help of carrier frequency systems. In Germany this system was called wire radio , in Switzerland it was the telephone broadcast .
- Long wave broadcasting | Long wave transmitter
- List of radio beacons
- Frequency plan of the Federal Network Agency
- JA Adcock (VK3ACA): Propagation of long Radio Waves ( Memento from February 22, 2014 in the Internet Archive )
- ↑ Frequency plan of the Federal Network Agency ( Memento from January 31, 2016 in the Internet Archive ) (PDF; 4.8 MB)