Question 6A548

LORAN (Long Range Navigation) systems identify their transmitting stations through a combination of methods. The primary method for distinguishing between different LORAN chains (groups of synchronized stations) is by their **pulse recurrence rate (PRR)**. In LORAN-C, this is specifically known as the Group Repetition Interval (GRI). Each LORAN chain transmits its pulses at a unique, precisely timed interval, allowing a receiver to lock onto and identify a particular chain. Additionally, the **frequency of transmission** is crucial for initially identifying the signal as a LORAN transmission. For instance, LORAN-C systems operate on a specific frequency (e.g., 100 kHz). Tuning to this frequency helps filter out other radio signals, confirming that the received signal is indeed from a LORAN system. Once on the correct frequency, the PRR then differentiates between the various LORAN chains. Therefore, both the frequency and the pulse recurrence rate are used to identify the transmitting stations.