Regulation 35 Calibration
The master of every ship required to be fitted with a direction-finder installation shall cause the direction-finder installation to be calibrated in accordance with this regulation as soon as practicable after it has been installed in the ship and whenever any change is made in the position of the direction-finder antenna system.
The direction-finder installation shall be calibrated by two persons, one being experienced in the taking of radio bearings and the other experienced in the taking of visual bearings. The calibration shall be carried out by taking simultaneous radio and visual bearings of a transmitter, and such bearings shall be taken at intervals of not greater than 5 degrees throughout 360 degrees on a frequency between 283.5 kHz and 315 kHz.
Calibration tables and curves which enable radio bearings obtained by the direction-finder installation to be adjusted to within two degrees of the correct bearing shall be prepared on the basis of the bearings taken in accordance with paragraph (2)(a) of this regulation.
Following satisfactory calibration and the preparation of calibration tables and curves, a Certificate of Calibration of Direction-Finder shall be completed in the form specified in Schedule 1 to these Regulations.
The master of every such ship shall cause the calibration tables and curves prepared in accordance with the foregoing provisions of this regulation to be verified by check bearings or by a further calibration whenever any changes are made in the position of:
any antennas; or
any structure on deck; or
the arrangement of cargo above deck,
which might affect appreciably the accuracy of the direction-finder.