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中短波调幅广播发射机,近年来的技术进步是非常惊人的。主要表现在发射机的固态化、数字化和自动化的程度越来越高。典型代表是Harris公司的DX系列和Thomcast公司的M2W数字调制发射机。这类发射机的共同优点是,有最高的整机效率、特别高的电声指标和运行可靠性。同时,这类发射机的设计,已经为模拟AM广播将来过渡到中、短波数字声音广播(简称数字AM)做了周密的考虑。 采用数字调制方式的调幅发射机,把传统大功率调幅发射机的高压整流电源(通常称为主整)、调制器和射频功率放大器,合并为一个系统。全机由许多RF功率放大器单元组成,其直流供电电压仅300多伏。RF功率放大器的输出电压缓合成后,达到发射机所需的功率电平。 数字调制方式的调幅发射机,信号处理的简要工作过程是:模拟音频信号(决定边带电平)和直流电压(决
Shortwave AM AM transmitters, the technical progress in recent years is very alarming. Mainly reflected in the transmitter solid-state, digital and automation degree is higher and higher. Typical representatives are Harris DX series and Thomcast’s M2W digital modulation transmitter. The common advantage of these transmitters is that they have the highest overall efficiency, particularly high electroacoustic specifications and operational reliability. At the same time, the design of such transmitters has been carefully considered for the future transition of analog AM broadcasting to medium and shortwave digital sound broadcasting (AM). The use of digital modulation AM transmitters, the traditional high-power amplitude modulation transmitter high-voltage rectifier power supply (commonly known as main), modulator and RF power amplifier, into a system. The whole machine consists of many RF power amplifier unit, the DC supply voltage is only 300 volts. After the output voltage of the RF power amplifier is gently combined, the power level required by the transmitter is reached. Digital Modulation AM transmitters, signal processing is a brief process: analog audio signal (to determine the sideband level) and DC voltage