M~2W Transmitter Carrier Alarm System

The medium wave frequency broadcasting is covered with a modular medium wave radio transmitter(Modular Medium Wave,M~2W).The high frequency carrier is used as the carrier to modulate the effective audio envelope signal into the modulated wave,and the power amplifier module of the transmitter is used to increase the power coverage of the specified area.Therefore,the stable operation of the transmitter is the basis of ensuring the normal broadcasting.The carrier signal of the transmitter is a reference standard for determining the normal operation of equipment.It is the main research direction of this paper to use monitoring means to quickly and accurately judge,shorten the time of failure and restore normal broadcasting in emergency.In this paper,the electromagnetic wave and field strength of the transmitter are analyzed according to the working mechanism of the transmitter.On this basis,the hardware monitoring system is developed independently to monitor and alarm the transmitter effectively.It can reflect the fault frequency to the duty personnel promptly and accurately after the transmitter's carrier is lost,so that the duty officer can make prompt analysis and take measures to resume broadcasting as soon as possible.At the same time using the RF transmission line from the transmitter to the modulated wave signal coupling holes into the duty room,duty room designed carrier alarm and audio monitoring device.The electromagnetic wave detection probe is installed to the top of the transmitter filter network,and the trigger device sends out acoustooptic alarm.Due to the complexity of the electromagnetic environment,the test data analysis of the field strength tester,we have measured the electromagnetic intensity after many experiments,and determined the suitable location of the electromagnetic wave detection probe.In addition,the use of radio frequency cable,leads to high frequency carrier modulated transmitter from the carrier coupling apertures,developed audio monitoring alarm,double function device.Use envelope detection principle,the modulation of audio signal from detector carrier envelope,into a voltage comparator threshold determination,the transmitter power value is different,according to the proportion of adjustment of the audio intensity and setting threshold,when trigger threshold of alarm in room to achieve real-time and effectively judge.At present,two sets of monitoring system developed in this paper have been put into use.When the transmitter loses carrier,the two sets will send out the alarm prompt and precisely lock the fault frequency point,so as to provide basis for the duty officer to process quickly.