One for the Sparkers

What is the  type of propagation used by this antenna?

Capture

 

Answer – Near Vertical Incident Skywave (NVIS)
This aerial is ideal for use for communications between 5 and 650 km where groundwave propagation is not able to travel over mountainous terrain or through thick bush/jungle foliage. The concept was enhanced by Major John Shirley of the RNZ Signals attached to the Royal Signals during the Malayan Emergency to aid communications during jungle warfare. The aerial illustrated was not the one in use, but the concept was the same. Basically, the aerial had to be fairly close to the ground. so that the emission would radiate as close as possible to the vertical for the frequency selected.
HMNZS Irirangi used the above aerial design for the  8 and 3 MHz Coastal Common Net in the 1980s to enable ships in ports to the west and east coasts of NZ to communicate back to Waiouru. There was a groundwave component but this was quickly absorbed by the mountainous terrain.
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4 Responses to One for the Sparkers

  1. Trev Appleton says:

    The type of propagation used by this aerial is known as ‘Sky-wave’ propagation.

    The antenna shown is a Fan dipole NVIS (Near Vertical Incidence Sky-wave) base station antenna.

    Wire dipole antennas have always been sited so that the broadside of the antenna was pointed toward the receiving station(s).
    This is still the correct approach for long-haul paths.
    This antenna orientation is not necessary when using the NVIS mode.
    For NVIS operation, antenna orientation does not matter since all the energy is directed upward and returns to earth in an omnidirectional pattern.
    The fan dipole provides more frequency flexibility (for example, day, night, and transition period frequencies).
    For tactical communications, these dipoles can be easily deployed in a field expedient manner because they can be located close to the ground.

  2. Chuck & Ali Berry says:

    Wouldn’t be 2-18MHZ range would it ?

  3. Jim Paltridge says:

    Sky Wave

  4. John Bullock says:

    I think I will go with a Satellite Smartphone, less complicated, and more reliable! I gave up on wire antenna array, especially after the maintenance that was required on the Leander’s “Main Roof”, including cleaning the soot off the numerous funnel insulators …. they were the days!

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