Tham khảo tài liệu 'electronic navigation systems 3 part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Loran-C 139 PF Primary Phase Factor. A correction factor applied to a Loran-C signal reading made necessary by the difference in signal propagation through the atmosphere as opposed to propagation in free space. The speed of Loran-C signals through the atmosphere is equal to the speed through free space divided by the atmospheric index of refraction. The speed is taken as X 108 ms-1. PRF PRR Pulse Repetition Frequency Pulse Repetition Rate. The number of pulses transmitted in a specified time. For the Loran-C system the PRF PRR is given by the reciprocal of the GRI. Hence a chain with a GRI of 80000 ps would have a PRF PRR of Hz. Root mean square RMS Secondary coding delay That value of a time varying signal which has the equivalent heating effect to that of a . quantity. That time interval in microseconds between when a secondary station receives the master transmission and a transmission occurs from the secondary station. Secondary phase factor sF That amount of time in microseconds by which the predicted time differences TDs of a pair of Loran-C station signals travelling over an allseawater path differ from those that travel through the atmosphere. Secondary station One of the possible maximum number of five stations that together with the master station comprise the Loran-C chain. Signal-to-noise ratio SNR or S N The ratio of signal strength compared to the strength of electrical noise present with the signal in a given bandwidth. The coverage diagrams for Loran-C are calculated using an SNR of at least 1 3. SNR is often quoted in decibels db where the db value is given by 20log10 SNR so that with an SNR of 1 3 the decibel value is - which is often approximated to -10db. Single-rated SR Those stations in a Loran-C chain which do not share transmissions with other chains. Compare with Dual-rated. Speed Rate of travel. For a vessel travelling relative to the water over a horizontal distance the speed of the vessel is measured in knots. .
