| Explaination:
In the original Loran of the 1940 s, single pulses were transmitted and slaves operated on different frequencies with particular allocated pulse recurrence frequencies (PRF). Now Loran-C signals are transmitted in groups of pulses. The pulse groups recur at a fixed group repetition interval (GRI), the value of which is different for each chain (and designated by a code). In order to achieve the greatest efficiency, the time difference is read from the third cycle within a group of pulses from the master and from the chosen slave. This process is also known as 'indexing'. |
