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短波通信的研究和应用,已有六十几年的历史。但是由于电磁波传播受到电离层的影响而不够稳定,二十年代还未能广泛应用。以后短波通信技术不断改进和发展,如单边带技术,分集接收、移频键控,以及高增益定向天线的采用等,使短波通信质量有很大提高,于是使用者逐渐增多。四十至五十年代是短波通信的全盛时期,发展迅速,应用广泛。但后来,使用者越来越多,短波频道变得拥挤不堪,干扰严重。同时,由于海缆通信技术的进步和卫星通信技术的发展,便使得大容量远程的定点通信电路逐渐为海缆通信和卫星通信所代替。尽管如此,在小容量远程的定点通信、移动通信(包括航海、航空)及其他特殊用途的通信方面,短波通信仍有使用灵活、电路简单的优点,加上电报终端采
Research and application of shortwave communications, has sixty years of history. However, due to the influence of ionosphere electromagnetic wave propagation is not stable enough, the twenties has not been widely used. After the continuous improvement and development of shortwave communication technology, such as single-sideband technology, diversity reception, frequency shift keying, and the use of high-gain directional antennas, so that the quality of short-wave communications has greatly improved, so the user gradually increased. The forties and fifties were the heyday of shortwave communications with rapid development and wide application. But then, more and more users, shortwave channels become crowded, serious interference. At the same time, due to the progress of submarine cable communication technology and the development of satellite communication technology, high-capacity long-distance fixed-point communication circuits are gradually replaced by submarine cable communications and satellite communications. In spite of this, the shortwave communication still has the advantages of flexible use and simple circuit in small-capacity remote fixed-point communication, mobile communication (including navigation and aviation) and other special-purpose communications. In addition, telegraph terminal