Q.1. When switching on the weather radar, after start-up a single very bright line appears on the screen. This means that the:
scanner is not rotating
scanning of the cathode ray tube is faulty
Q.2. On switching on the AWR a single line appears on the display. This means that:
the CRT is not scanning
the antenna is not scanning
Whats the main difference between the two?
The main difference appears to be the use of the words "very bright" in question one. If the electron gun in the CRT is repeatedly scanning either vertically or horizontally, instead of both vertically and horizontally, this will concentrate the energy in a single line. This concentration of energy is likely to make the line very bright. In this case the most accurate answer would be "scanning of the cathode ray tube is faulty".
For question 2, if the CRT is working correctly but the antenna is not scanning, then only the radar returns from the area in line with the scanner would be displayed. Whether or not these would produce a very bright line would depend upon what returns were being received from that area.