LORAN-C (LONG-RANGE NAVIGATION)
Although Loran-C is not used this much these days, due to GPS, thought I'd give it a brief mention. Just like Loran A it will become obsolete. Loran-C is a low frequency hyperbolic system broadcasting on a frequency of about 100 kHz. The hyperbolic pattern is established through the measurement of time differences (TD) of pulsed signals. The Loran-C system was designed to cover the U.S. coastal confluence zones and is also present in key coastal areas throughout the Northern Hemisphere. Loran-C coverage is divided into chains composed of 3 to 5 land-based transmitting stations consisting of a master station and 2 to 4 slaves. Each slave is designated as W, X, Y, and Z. Each station transmits a group of pulses at a specific rate called the group repetition interval (GRI). This is partly how the receiver determines the differences between chains as all Loran stations transmit on the same frequency. The master station broadcasts 8 pulse modulated signals followed by each slave station in order, broadcasting 8 signals as well. There is also a 9th pulse broadcast by the master station called the performance pulse. This indicates the efficient operation of the system overall. Broadcasting at a specific GRI, signals are received at the specific rate designated for that chain. The hyperbolic pattern is established between the master and each of the slaves with the baseline between the master and each slave. There is approximately an average separation of 650 nautical miles between the master and each slave and the difference between each hyperbolic line (TD) is expressed in microseconds.
The navigator reads the microsecond difference off his receiver and finds the closest TDs on either side of his or her reading. He or she then measures the gradient between the two TDs and interpolates where the LORAN-C (LONG-RANGE NAVIGATION) Loran-C is a low frequency hyperbolic system broadcasting on a frequency of about 100 kHz. The hyperbolic pattern is established through the measurement of time differences (TD) of pulsed signals. The Loran-C system was designed to cover the U.S. coastal confluence zones and is also present in key coastal areas throughout the Northern Hemisphere (see figures 6-3 and 64). Loran-C coverage is divided into chains composed of 3 to 5 land-based transmitting stations consisting of a master station and 2 to 4 slaves. Each slave is designated as W, X, Y, and Z. Each station transmits a group of pulses at a specific rate called the group repetition interval (GRI). This is partly how the receiver determines the differences between chains as all Loran stations transmit on the same frequency. The master station broadcasts 8 pulse modulated signals followed by each slave station in order, broadcasting 8 signals as well. There is also a 9th pulse broadcast by the master station called the performance pulse. This indicates the efficient operation of the system overall. Broadcasting at a specific GRI, signals are received at the specific rate designated for that chain. The hyperbolic pattern is established between the master and each of the slaves with the baseline between the master and each slave. There is approximately an average separation of 650 nautical miles between the master and each slave and the difference between each hyperbolic line (TD) is expressed in microseconds.
The navigator reads the microsecond difference off his receiver and finds the closest TDs on either side of his or her reading. He or she then measures the gradient between the two TDs and interpolates where the
