Fruit (radar)
In the secondary radar, fruit is the term used to describe all interference caused by responses that were not triggered by your own query.
Secondary radar systems all work worldwide on the same carrier frequencies - e.g. B. for the query to 1030 MHz and for the answer to 1090 MHz. This is necessary because an aircraft traverses several radar detection areas on its flight path . Due to the relatively dense network of radar devices and the high volume of flights , many flight destinations are queried from different stations and respond accordingly frequently. The probability that the radar stations will interfere with one another increases with increasing air traffic.
Since in the majority of cases such responses do not occur synchronously with your own query, they are also called "non-synchronous disturbances". They can therefore be eliminated with a synchronous filter "which checks all responses received for synchronism with its own query sequence and suppresses the responses that are not synchronous". Such a filter is called a defruiter.
The word Fruit is a made-up word. There are several meaningful interpretations in circulation, e.g. B.
- F alse R eplies U nsynchronuous I n T ime (= non-synchronous wrong answers) or
- F alse R eplies U nsynchronised to I nterrogator T ransmission (= false responses not synchronous to the interrogator).
According to another source, the term "fruit" comes from the fact that the "interference characters [...] resulting from unwanted responses [...] when displayed on the screen [result] in an image structure reminiscent of a halved grapefruit".
Individual evidence
- ^ A b Werner Mansfeld: Radio location and radio navigation systems . Ed .: Center de dialectologie, Université de Neuchâtel. Hüthig Buch Verlag, Heidelberg 1994, ISBN 3-7785-2202-7 .