ABSTRACT
The 1090 MHz radio-frequency band is the key band used by cooperative surveillance systems in the aviation. The various types of surveillance systems and different modes of its operation has significant influence to the frequency band load. The article analyses the contributions of particular types of systems based on measurement of replies emitted by on-board transponders in the airspace of the Czech Republic region. The types of messages that the most negatively contribute to the load of the band were identified. The downlink format 11 messages have been identified as the most problematic in terms of their benefits and quantities. The source of existences of their large number is shown in the article and outlined potential steps that could help to mitigation the amount of such replies are identified. On the other hand there is explained how these messages can be successfully used to get an independent overview of the SSR Mode S radar operational coverage.
