Editing Ground wave (section)

==Applications==

Most [[Low frequency|low-frequency]] radio communication is via groundwave propagation. Groundwave is also the primary mode for [[Medium frequency|medium frequencies]] during the day when skywave is absent, and can be useful at high frequencies at short ranges. Uses include navigation signals, low-frequency time signals, longwave radio, and AM radio. The increased effectiveness of groundwave at lower frequencies gives AM radio stations more coverage at the low end of the band. High frequency over-the-horizon radar may use groundwave at moderate ranges but skywave at longer distances. Military communications in the very low and low frequency range uses ground wave, especially to reach ships and submarines, as groundwaves at these long wavelengths penetrate well below the sea surface.<ref name=":0" />

In the [[invention of radio|development of radio]], ground waves were used extensively. Early commercial and professional radio services relied exclusively on [[long wave]], low frequencies and ground-wave propagation. To prevent interference with these services, amateur and experimental transmitters were restricted to the high frequencies (HF), felt to be useless since their ground-wave range was limited.  Upon discovery of the other propagation modes possible at [[medium wave]] and [[short wave]] frequencies, the advantages of HF for commercial and military purposes became apparent. Amateur experimentation was then confined to only authorized frequencies in the range.