The Testing Device For Weather Facsimile Receiver

The weather facsimile receiver is an important device to obtain meteorological information during the course of the ship's maritime navigation.Its development and testing work can not be separated from the weather facsimile signal transmitted by the weather fax transmitting station.Due to the weather,geographical location,signal interference and program time period,the weatherl facsimile signal can not be received in all weathers and all time periods.Therefore,there are many limitations when testing the weather facsimile receiver.In recent years,with the continuous development of shortwave communication technology and the deepening of software radio technology,it is possible to develop a small-scale weather signal transmitting station suitable for debugging of meteorological facsimile receivers.In this paper,according to the requirements of wireless weather facsimile receiver,the paper analyzes the principle of fax communication,and proposes a design scheme of test device including weather facsimile signal transmission and system display and control terminal.The display and control end of the system is embedded with the single board computer as the core.The Linux operating system is used to control the short-wave transmitter and the weather facsimile receiver through the graphical interface.At the same time,the running status of the system equipment and facsimile receiving data are displayed.Direct digital frequency synthesis technology,the design of short-wave radio stations,can be issued by the World Meteorological Organization(WMO)specified in the 2-24 MHz frequency between the radio stations optional carrier.The device can simulate the transmission of arbitrary set of stations of the weather fax image signal,and meteorological fax receiver to receive the fax image signal and the transmission image signal display contrast.Shortwave transmitter software has two modes for users to choose: single-board mode and machine mode.In the single-board mode,the short-wave transmitter is not controlled by the embedded single board computer,and the weather fax image signal of the commonly used station is customized according to the user's requirements.In the whole mode,the shortwave transmitter is controlled by the embedded single board computer,and the parameters of the shortwave transmitting end are set through the graphical interface to realize the simulation of various radio stations.Display and control software consists of the application and graphical interface components.Through USB the embedded single board computer controls the short wave transmitter,and through ethernet controls the weather facsimile receiver,and processes the image data received by the weather facsimile receiver.This paper completes the design of the system and the key software and hardware development scheme of the weather facsimile testing device,and carries on the system verification test.The meteorological facsimile image signal transmitted by the weather facsimile test apparatus can bereceived by the FAX-30 weather facsimile machine and the image is very clear.The system test shows that the scheme can simulate meteorological station broadcast meteorological facsimile signal,to facilitate the test of meteorological fax receiver,to achieve the debugging environment of the equipment in the field.