Configuration of Inverted-V Dipole NVIS HF Antenna for Offshore Fast Patrol Boat

This paper describes the configuration of Inverted-V half-wave dipole antenna which was designed, simulated and deployed for offshore ship-patrol of a 28 Meter class Fast Patrol Boat (FPB) for its High Frequency (HF) communication system. The antenna is used for medium range of HF radio coverage by Near Vertical Incidence Skywave (NVIS) mode for sea to port and sea to sea communication scheme for radius around 300 kilometers. The effect of sea surface and ship's hull material on the radiation pattern was studied. Furthermore, the antenna height and the V-shape angle configuration were determined to compromise between the limited space, maximum antenna gain as well as its Standing Wave Ratio (SWR) value. The Numerical Electromagnetics Code (NEC) computer simulation describes not only the flat-bottomed radiation pattern due to high conductivity of the sea surface but also the 3-dB gain of the vertical main lobe as the typical characteristic of V-inverted dipole antenna. Designed antenna has the SWR value as low as 1.16 at 42-meter band with 40-degree angle of inverted V-shaped mounted on boat with 10 meters tall of mast above sea level coupled with a 100-Watt ICOM HF radio.