ElectroMagnetic Compatibility (EMC) standard for marine radio equipment and services; Harmonised Standard covering the essential requirements of article 3.1b of the Directive 2014/53/EU; -- Part 4: Specific conditions for Narrow-Band Direct-Printing (NBDP) NAVTEX receivers (ETSI EN 301 843-4 V2.1.1 (2016-03))