Abstract: The invention relates to a microwave landing system or MLS in which the bearing station and elevation station are geographically separated by a distance which can be several kilometers. Each of the elevation and bearing stations transmits a message constituted by a preamble identifying the nature of the following angular message. According to the invention, one of these stations is made the master station and the other becomes the slave station. Thus, one station, i.e. the master station transmits the preambles of both messages, the slave station now only transmitting its specific angular information.

Abstract: In a microwave landing system or MLS, the bearing and/or elevation angular messages are in two parts a preamble transmitted by a sector antenna and a specific message transmitted by an electronic scan or scanning beam antenna. As the gain of the sector antenna is below that of the scanning beam antenna, the preamble is much more vulnerable to scanning than the message.According to the invention, a preamble is transmitted, which is reinforced in a narrow angular sector and movable so as to cover the sector covered by the sector antenna by superimposing the radiation patterns of the sector antenna and the scanning beam antenna in said direction.