This standard specifies the technical requirements, test methods, inspection rules, marking, packaging, transportation and storage of Loran C receiving equipment for ships (hereinafter referred to as receiving equipment). This standard applies to Loran C receiving equipment used on ships. GB/T 12752-1991 General Technical Requirements for Loran C Receiving Equipment for Ships GB/T12752-1991 Standard Download Decompression Password: www.bzxz.net

National Standard of the People's Republic of China
GB/T 12752 ---1991
General specification for marine Loran-C receiving equipmentGcneral specification for marine Loran-C receiving equipment1991-03-21Promulgated
Implementation on 1991-11-01
State Administration of Technical Supervision
WNational Standard of the People's Republic of China
General specification for marine Loran-C receiving equipment1 Content and scope of application
GB/T 12752—1991
This standard specifies the requirements, test methods, inspection rules and marking, packaging, transportation and storage of marine Loran-C receiving equipment (hereinafter referred to as receiving equipment).
This international standard applies to marine Loran-C receiving equipment used on ships. 2 Reference standards
GB191 Packaging, storage and transportation pictorial marks
GB12267 General requirements and test methods for marine navigation equipment 3 Terminology
3.1 Loran C system
The Loran C system refers to a long-range radio navigation system operating at a frequency of 100kHz specified by the enterprise. The transmitting station chain of this system consists of a main station and two (or more) secondary stations. Each station transmits the Loran C signal (hereinafter referred to as the signal) at a fixed time, and the receiving equipment is used to measure the time difference between the signal and the receiving point to determine the hyperbolic position line, and the intersection of the position line determines the ship's position. 3.2 Receiving equipment
The receiving equipment refers to the general term for nominal antenna, antenna coupler, feeder cable and receiver. 3.3 Nominal antenna
The nominal antenna refers to the antenna specified and selected by the manufacturer. 3.4 Antenna coupler
The feeder cable coupler refers to the front part of the receiving equipment. It has functions such as filtering, amplifier and anti-conversion. 3.5 Reception Device
A receiver is a device that processes the signal from the antenna coupler and measures the arrival time difference of the selected signal. A receiver that can use the time difference to calculate and display navigation data such as longitude, latitude, heading, speed, and lateral track error can also be called a navigator,
3.6 Time of Arrival (TOA)
The arrival time refers to the time when the electric field of the pulse group from the transmitting station appears on the receiving line. 3.7 Time Delay (TD)
The time difference refers to the time of arrival of the secondary station signal minus the arrival time of the main station signal. 3.8 Repetition Interval (CRT)
The group repetition interval refers to the interval between the adjacent main (or desired station) signal pulse groups in units of 10us, and is also represented by four numbers from 4000 to 9999 to represent different Loran C transmitter chains. 3.9 Selection
Approved by the State Administration of Technical Supervision on March 21, 1997, and implemented on November 1, 1997
W.GB/T 12752 1991
Selection refers to the process of the receiving device selecting the station chain (i.e., selecting G1) and the station. 3. Search
Dual search refers to the process of establishing the time position of the master station and each selected secondary station. 3.11 Identification
Identification refers to the process of adjusting the phase tracking point to the zero crossing point of the carrier of the ground wave signal. Usually this process includes ground wave identification (front locking) and cycle identification (cycle selection). 3.12 Tracking
Tracking refers to the process of the receiving device keeping synchronization with the selected station signal. 3.13 Locking
Lock means that the receiving device has completed the search and identification and entered the acquisition state of tracking the selected station signal. 3.14 Locking time
The locking time is the time from powering on or changing the selected station chain to all the selected stations being locked. 3.15 Maximum locking time
The maximum locking time is the minimum value obtained in less than 10 rated time tests or the minimum value of 90% of the data after removing 10% of the data in more than 9 locking time tests. 3.16 Signal level (S)
The signal level refers to the effective level of the continuous wave with a peak value equal to the level at 251us after the start of the signal pulse envelope (see Figure 2). It can be expressed in microvolts, but is usually expressed as a negative number of field strength (0B-1μV/m). 3.17 Noise level (N)
Noise in this standard includes machine noise and simulated atmospheric noise. Random noise refers to the commonly used Gaussian white noise; the simulated atmospheric noise is composed of a linear superposition of random noise accounting for 15.5% of the total power and a Poisson's 100kHz single tone pulse accounting for 81.15% of the total power (see Figure 1).
Figure 1 100kHz tone pulse
For random sound, the sound level (N) refers to 2.5 times the root mean square value of the noise pressure on a 509 resistor load after passing through a single-pole filter with a center frequency of 100kHz and a 3dB bandwidth of 30kΩ (or 84B above the field strength decibel mark). For simulated atmospheric media sound, the noise level (N) is as follows: 2
W+X-
random noise level;
GB/T 12752—1991
N=/X\+WP(AX)\
W--100kHz single tone pulse width·W=30μus30×10-6g;P——the number of single tone pulses per second, usually P=40~60AX100kHz single tone pulse effective value;
A——constant. When P=50,
WPA* --84.15/15.85=5.309,A =59.53.18Signal-to-noise ratio (SNB)
Signal-to-noise ratio refers to the ratio of signal level to noise level, which can be expressed as a dimensionless number or decibel. 3.19 Continuous wave interference (CW1)
Continuous wave interference refers to various artificial radio frequency sources with energy sufficient to produce harmful effects on receiving equipment. Continuous wave interference can be divided into the following types: a. In-band interference: interference with carrier frequency in the frequency band of 90~110kHz; b. Near-band interference: interference with carrier frequency in the frequency band of 70~90kHz and 110~130kHz; b. Out-of-band interference: interference with carrier frequency lower than 70kHz or higher than 130kHz; d. Concentric interference: near-band interference determined by the carrier frequency (f.) as fN/2GRI
where N-1,2,3.Www.bzxZ.net
e. Odd-synchronous interference: synchronous interference with N being an even number in formula (2): , Even-step interference: synchronous interference with N being an odd number in formula (2); e. Near-synchronous interference: near-band interference with carrier frequency satisfying the following formula IF.-N/2GRI:
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