Low Frequency or LF (sometimes called longwave) refers to Radio Frequencies (RF) in the range of 30-300 kHz. In Europe, part of the LF spectrum is used for AM broadcast service. In the western hemisphere, its main use is for aircraft beacon, navigation (LORAN), information, and weather systems. Time signal stations MSF, DCF77 and WWVB are found in this band.

In the USA, the portion between 160 and 190 kHz can be used for experimental purposes and is sometimes called the "Lost Band". Unlicensed operation by the public is permitted south of 60 degrees north latitude, except where interference would occur to 10 licensed location service stations located along the coasts. Regulations for use include a power output of no more than 1 watt, and an antenna/ground-lead length of no more than 15 meters, and a field strength of no more than 4.9 microvolts/meter. Also, emissions outside of the 160-190 kHz band must be attenuated by at least 20 dB below the level of the unmodulated carrier. Amateur Radio operators experiment in this band.

The UK's 73-kHz band is a 2.8 kHz sliver of spectrum, from 71.6 to 74.4 kHz and has been available to Amateur Radio operators since April 1996. They must apply for a Notice of Variation to use the band on a noninterference basis with a maximum output power of 1 W ERP (effective radiated power). A 1-watt transmission of very slow Morse Code between G3AQC (in the UK) and W1TAG (in the USA) spanned the Atlantic Ocean for 3275 miles on November 21-22, 2001.

A 136 kHz allocation (135.7 to 137.8 kHz) band is available to French Radio Amateurs with a maximum ERP of 1 W. The new ruling includes French territories such as Guadeloupe, French Guyana, Martinique and Saint Pierre et Miquelon. Canada and the UK also allow licensed Radio Amateurs to use this allocation with special permits.