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Beacon DGPS Broadcasting Stations Network

Overview

The original purpose of marine radio beacons was to provide signals for use by radio direction finders for coastal navigation. The frequencies allocated are in the range of 283.5 - 325.0 KHz. Depending on radiated power and environmental conditions, the beacon signals have a range from 10 - 250 Nm. Beacon systems have a number of advantages for broadcast of DGPS corrections. They are in place and maintained, have broad existing coverage, have the necessary frequency allocation, are relatively inexpensive to purchase and operate, and have sufficient power to provide an adequate range for coastal navigation. The modifications to the beacons to enable broadcast of DGPS corrections are straightforward, and do not cause any interference with direction finding. Also, the radio beacon equipment is reliable, and receivers for the Medium Frequency (MF) beacon signals are not inherently complex. All of these reasons have made beacons the logical candidate for worldwide coastal DGPS

MX Marine group of Magnavox developed the first Beacon DGPS system in 1990. The first Beacon Modulator MX50M and Beacon receiver MX50R were used by Maritime agencies for testing the Beacon DGPS systems with their Beacon transmitters. Many Beacon stations are at unmanned remote locations and therefore it was necessary to monitor the Broadcast Station from remote location. The first such system was developed and delivered by MX Marine based on DOS based operating system. Each broadcast station was developed with two DGPS reference Stations, one Integrity Monitor and control PC software at Broadcast station and Central station. Modems with phone lines were used for communication between Broadcast station and central control station.

In 1996 MX Marine developed a New Generation of DGPS Broadcasting Stations Network. The network was developed as per the relevant standards and recommendations of the RTCM (Radio Technical Commission of Maritime Services), IALA (International Association of Lighthouse Authorities), and ITU (International Telecommunications Union). A paper (A New Generation of DGPS Broadcasting Stations) was published in ION (Institute of Navigation) conference in September 1988. A copy of this paper can be downloaded from publications menu. More than 100 such systems are supplied by MX Marine and are in operation all over the world.

A Typical Control Station consists of the following equipment:

  • A Computer
  • Printer
  • One Uninterruptible Power Supply (UPS)
  • TCP/IP Network or Modem

A DGPS Broadcasting Station consists of the following equipment:

  • Two Reference Stations Antennas
  • Two Reference Stations
  • Two Modulators With LF Carrier Generators
  • Two Beacon Transmitters
  • One RF relay changeover assembly
  • 50 Ohms Dummy Load (optional)
  • One GPS Integrity Monitor Antenna
  • One GPS Integrity Monitor (IM) Receiver, With Differential Corrections Capability
  • One LF Broadcast Integrity Monitor Receiver (Beacon Receiver)
  • One Broadcast Station Controller PC for Monitoring, Control And Data Logging And Associated Software
  • One optional Uninterruptible Power Supply (UPS)
  • One Electromagnetic Interference Equipment Rack
  • Interconnecting Cables

Figure 1 Beacon DGPS System with DOS Operating System

Figure 2 DGPS Network Block Diagram

Figure 3 A New Generation Beacon DGPS Base Station