在20世纪40年代，空中交通管制中心能够而且确实利用了第二次世界大战中新研制的雷达和改进的无线电通讯，但是这个系统还处于初级阶段。
In the 1940s, ATC centres could and did take advantage of the newly developed radar and improved radio communication brought about by the Second World War, but the system remained rudimentary.
不过航空运输延迟和低效的主要原因还是过时的空中交通管制——一套依靠地面控制、反应迟缓的雷达站和不断重复的语音通讯建立起来的体系。
But delays and inefficiencies in air travel are due in large part to an outdated traffic-control system that still relies on slow, ground-based radar stations and repetitive voice communication.
该波段在各种远距离地面通讯或雷达工作中，均不能应用。
The wave band in each kind of long-distance range ground communication or the radar work, can not apply.
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