Longwave

[8] Non-directional beacons transmit continuously for the benefit of radio direction finders in marine and aeronautical navigation.

There are institutional broadcast stations in the range that transmit coded time signals to radio clocks.

Those higher-frequency signals do not follow the surface of the Earth beyond a few kilometers, but can travel as skywaves, 'bouncing' off different layers of the ionosphere at different times of day.

The delay between when the long-wave signal was sent from the transmitter (when the coded time was correct) and when the signal is received by the clock (when the coded time is slightly late) depends on the overland distance between the clock and the transmitter and the speed of light through the air, which is also very nearly constant.

In North America during the 1970s, the frequencies 167, 179, and 191 kHz were assigned to the short-lived Public Emergency Radio of the United States.

Nowadays, in the United States, Part 15 of FCC regulations allow unlicensed use of the 160–190 kHz band a transmitter / amplifier output power to the antenna of at most 1 watt, with an antenna at most 15 meters (49 feet) high; this is called Low Frequency Experimental Radio (LowFER).

Although the station ended regular service in 1996, it has been maintained as a World Heritage Site, and makes at least two demonstration transmissions yearly, on 17.2 kHz.

Typically, a larger geographic area can be covered by a long-wave broadcast transmitter compared to a medium-wave one.

One exception was a French-language station, Europe 1 in Germany, which retained its prior channel spacing until the long-wave service was terminated in 2019.

[clarification needed] Until the 1970s, some long-wave stations in northern and eastern Europe and the Soviet Union operated on frequencies as high as 433 kHz.

Droitwich also broadcasts a low bit-rate data channel, using narrow-shift phase-shift keying of the carrier, for Radio Teleswitch Services.

Because long-wave signals can travel very long distances, some radio amateurs and shortwave listeners engage in an activity called DXing.