RADAR REFLECTOR
A simple radar reflector consists of three triangular plates mutually a right angles to one another. Any ray of energy that hits the inside face of any one of the three plates must, after reflecting off, return in the opposite direction.
RAMARK
A RAMARK is a radar beacon that works continuously, whether any ship is nearby or not. Its name is derived from RAdar MARKer. It transmits signals in all directions, covering the entire marine radar band . When the own ship’s Radar scanner points to the Ramark beacon, signals of the Ramark are received and painted as a series of dots.
Since these signals show up continuously during the entire formation of a trace, they extend, from the centre, all the way up to the edge of the screen, regardless of whether the Ramark beacon lies inside or outside the range scale in use at that time. Since it is not possible to determine which of these dots is the normal echo of the structure of the Ramark beacon, Ramark gives only the bearing of the beacon, but not its range.
Because of this, and also the fact that Ramark signals clutter up the PPI along the bearing of the beacon, Ramarks are practically obsolete, being replaced by Racons.
RACON
A Racon is a radar responder beacon. Its name is derived from RAdar beaCON. When the ship’s pulse arrives at the Racon, the Racon amplifies and returns the pulse to the scanner as a fairly strong signal of the same frequency. This signal creates a short, bright line on the PPI. Because of a slight, pre-set, time delay, the signal of the Racon arrives after the normal echo of the structure of the beacon. The result is an exclamation mark whose dot is the correct position of the Racon. Bearing and range of the Racon are, therefore, available.
At longer ranges, the normal echo of the structure of the beacon may not paint on the screen. The closer edge of the line may then be taken to be the position of the beacon and the resulting error in range will be very small.
Once a Racon responds to a particular frequency, it will not respond to that frequency again for a few minutes.
In order that a Racon will not unnecessarily respond to ships that are too far away to use the Racon signals, the Racon is adjusted such that it will not respond unless the ship’s pulse that arrives is above a predetermined signal-strength.
Because of this, the effective range of a Racon is only about 30 NM or so. Where several buoys, etc., in the same locality have Racons fitted on them, the Racon signal of each object is so designed as to appear as a different Morse letter, for identification purposes.
