自二次世界大战以后无线电工程一日千里获得了飞速的发展往往衡量一个国家的科学技术水平可以先看这个国家的电子工业发展的情况。虽然这样的分析很不全面但也可以略窥全貌一个国家的科技水平高那末它的电子工业也一定发达。二次世界大战后出现许多新的电真空器件以适应新的整机的需要,这些电真空器 Since the Second World War, radio engineering has enjoyed rapid development. The measure of a country's science and technology often can look at the development of the country's electronics industry. Although such an analysis is not comprehensive but it can also provide a glimpse into the picture of a country's high level of science and technology so that its electronics industry will certainly be developed. After the Second World War, many new vacuum devices appeared to meet the needs of the new machine. These vacuum devices