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Communication

So, more numbers are needed. Therefore, some are “reused”. In order to

reuse/use the same frequency for another station, there must be a reasonably

large geographical distance between the 2 stations with the same frequency.

The range depends on the flight altitude and can easily reach 100 NM.

4.4.3.1 Frequency protection

To avoid disturbing other radio stations, a concept called frequency protection

has been introduced.

Frequency protection is stated in brackets after the frequency, e.g. (150/50 NM).

This means that you must be within a radius of 50 NM from the radio station and
below flight level 150 before you can call on the frequency.

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Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 375