Most modern radio systems and devices use wavelengths which would then have been considered 'ultra-short'.
In contemporary usage, the term longwave is not defined precisely, and its precise meaning varies.
In 20 Russia closed all of its LW broadcast transmitters.
Because long wave signals can travel very long distances, some radio amateurs and shortwave listeners engage in an activity called DXing.
Low frequency ground waves can be received up to 2,000 kilometres (1,200 mi) from the transmitting antenna.
Low frequency waves can also occasionally travel long distances by reflecting from the ionosphere (the actual mechanism is one of refraction), although this method, called skywave or "skip" propagation, is not as common as at higher frequencies.
Reflection occurs at the ionospheric E layer or F layers.
Sometimes the upper limit is taken to be higher than 300 k Hz, but not above the start of the medium wave band at 520 k Hz.Some radio broadcasters, for instance Droitwich transmitting station in the UK, derive their carrier frequencies from an atomic clock, allowing their use as frequency standards.Droitwich also broadcasts a low bit-rate data channel, using narrow-shift phase-shift keying of the carrier, for Radio Teleswitch Services.Long-wave carrier frequencies are exact multiples of 9 k Hz; ranging from 153 to 279 k Hz, except for a French language station Europe #1 in Germany.This station did keep to correctly spaced channels spacing for 4 months—only 7 years ago, and all Mongolian transmitters are 2 k Hz above the internationally recognized channels.