Communication between ship and shore, when the ships are sailing on coastal waters, is usually conducted in the VHF band for very short ranges and at mf and low hf frequencies, up to say 4 MHz, for ranges up to several hundred miles. Propagation at mf is essentially by the ground wave mode. However, the addition of skywave modes at night, while increasing the potential coverage area, also increases the mutual interference levels of cochannel stations and creates a self interference zone where the ground and sky waves are of comparable amplitudes. This article examines the ground wave propagation mode. An assessment is made of the coverage range taking account of the system parameters, of the propagation and noise characteristics and of the distance of the shore station from the coast. The optimum frequency for ground wave communication, for a particular system, is indicated. The effect of sky wave propagation on the conclusions reached is discussed. The interference fading zone, where the ground and sky wave are comparable, is usually regarded as being unusable by broadcast organizations. The results of some experimental work are presented which show that, for communication quality ssb telephony, operation may be extended through the fading zone. An alternative solution for the coastal communication requirement would be to use an inland site and to rely solely on sky wave propagation modes. This possibility is examined and it is shown that, for a U. K. coastal coverage, the available frequencies at night limit the communication to the low part of the hf band where the spectrum is already very crowded.

  • Corporate Authors:

    GEC Large Machines Limited

    Mill Road
    Rugby CV21 1BD, Warwickshire,   England 
  • Authors:
    • Barclay, L W
  • Publication Date: 1977

Media Info

  • Features: References;
  • Pagination: p. 102-116
  • Serial:
    • Marconi Review
    • Volume: 40
    • Issue Number: 205
    • Publisher: GEC Large Machines Limited

Subject/Index Terms

Filing Info

  • Accession Number: 00173118
  • Record Type: Publication
  • Source Agency: Engineering Index
  • Files: TRIS
  • Created Date: Apr 26 1978 12:00AM