Editing Very low frequency (section)

=== Early wireless telegraphy ===
Historically, this band was used for long distance transoceanic radio communication during the [[wireless telegraphy]] era between about 1905 and 1925. Nations built networks of high-power LF and VLF [[radiotelegraphy]] stations that transmitted text information by [[Morse code]], to communicate with other countries, their colonies, and naval fleets. Early attempts were made to use radiotelephone using [[amplitude modulation]] and [[single-sideband modulation]] within the band starting from 20&nbsp;kHz, but the result was unsatisfactory because the available bandwidth was insufficient to contain the [[sideband]]s.

In the 1920s the discovery of the [[skywave]] (skip) radio propagation method allowed lower power transmitters operating at [[high frequency]] to communicate at similar distances by reflecting their radio waves off a layer of [[ionization|ionized]] atoms in the [[ionosphere]], and long-distance radio communication stations switched to the [[shortwave]] frequencies. The [[Grimeton VLF transmitter]] at Grimeton near Varberg in [[Sweden]], one of the few remaining transmitters from that era that has been preserved as a historical monument, can be visited by the public at certain times, such as on [[Alexanderson Day]].