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5.155B in the Radio Frequency Table Allocation of Ireland.

Content Type
ITU FOOTNOTE
Title
5.155B
Description
The band 21 870-21 924 kHz is used by the fixed service for provision of services related to aircraft flight safety.
Source
https://search.itu.int/history/HistoryDigitalCollectionDocLibrary/1.43.48.en.101.pdf