天线距离A点为10米；无线电波频率为900MHz，不考虑穿墙损耗和衰落损耗，其自由空间损耗为多少
A. 50.55
B. 51.55
C. 52.55
D. 53.55
查看答案
天线是将传输线中的电磁能转化成自由空间的电磁波或将空间电磁波转化成传输线中的电磁能的设备。
A. 对
B. 错
ITU-RP.1238传播模型分视距（LOS）和非视距（nLOS）两种情况。
A. 对
B. 错
In fact, multimedia is just two media: and .
A. sound, video
B. pictures, video
C. animations, text
D. sound, pictures
Which of following statements is incorrect?
A. Multimedia is a kind of computer technology.
B. Multimedia is the combination of PCs and TV.
C. Multimedia is a mix of machine and ideas.
D. Multimedia is a form of communication.
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