(1) 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.
(2) (a) 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.
(b) Calibration tables and curves, which enable radio bearings obtained by the direction-finder installation to be adjusted to within 2 degrees of the correct bearing, shall be prepared on the basis of the bearings taken in accordance with paragraph (a).
(c) 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.
(d) On each occasion that an arrangement of cargo carried above deck level varies significantly from an arrangement in respect of which the direction-finder installation has been calibrated, check bearings shall be taken, if practicable, to determine whether any substantial inaccuracy in the direction-finder installation is being caused by the arrangement of cargo. Where substantial errors are found, further check bearings shall be taken to establish a correction curve.
(3) 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 means of not less than four check bearings in each quadrant-
(a) at intervals not exceeding 12 months; and
(b) whenever any change is made in any structure or fitting on deck or in any rigging or antenna above deck which is likely to affect the accuracy of the direction-finder.
If such verification shall show that the calibration tables or curves are substantially inaccurate, the master of the ship shall cause the direction-finder to be recalibrated as soon as practicable in the manner specified in subregulations (2) and (3).
(4) In addition, bearings shall be taken in each quadrant, where practicable at intervals not exceeding 12 months, on a frequency at about 500 kHz. These bearings should not be substantially inaccurate after being corrected by use of the calibration curves.