WIRELESS AIDS

Evening Post, Volume CV, Issue 58, 9 March 1923, Page 8

WIRELESS AIDS

ASSISTANCE TO NAVIGATION EXPERIMENTS AT THE THREE KINGS RADIO BEACON STATION FAVOURED. The Marine Department recently carried out very complete experiments at the Three Kings concerning the application of wireless direction finding to marine navigation. The Government steamer Tutanekai was commissioned for the purpose, and an improved apparatus was installed upon the vessel. The Minister of Marine, the Hon. G. J. -Anderson, stated tho results of the tests to a representative of "The Post."

' "At present," he said by !w_ay of introduction, "there are two distinct principles in the application of wireless direction finding to marine navigation. These are: — "(1) By locating the direction finding stations in fixed positions on shore, from which the' ship receives its positioj through the medium of its ordinary wireless set. "(2) By installing directional receiving apparatus aboard the t ship—quite apart from the usual wireless equipment—and establishing a radio beacon on shore. "No. 1 principle has been fairly extensively applied in the Northern Hemisphere. It is "wholly confined to vessels equipped with wireless. No. 2 principle is the reverse of No. •1, and is the more up-to-date, and was recently tested by the Marine Department. "The apparatus on the s ship is part and parcel of -the ship's navigation equipment, and is worked by the navigation officer. Theri is no question of asking shore stations for a bearing with the probable necessity of waiting until the ship's turn arrives, - which, in foggy weather, or a congested area, where numerous ships are asking for bearings, may caus« serious delay. Check bearings can be taken as often as desired. Bearings may also be obtained on highpower wireless stations when the ship -is beyond the range of the established coastal radid-beacon station, or from an-, other ship if equipped with commercial wireless. . . "The radio-station on shore may be an ordinary commercial station, a naval radio station, or a coast beacon station, established especially for transmitting radio waves, either during foggy weather only or at regular periods as may be required or prescribed. ■ SUCCESSFUL TESTS. ."The Government steamer Tutanekai was utilised for the tests which were carried out during the last northern tour of the lighthouses and other Marine Department's interests. A radio beacon station was established on a selected site on the • Great King, the largest of the Three Kings Islands and an up-to-date direction finding instrument was installed in the navigation room on the vessel. Experienced wireless and navigation experts accompanied the vessel and conducted the tests. The shore station was situated about' the centre of the eastern end of the island; at an'altitude of 380 feet above sea level, from which the island rose gradually towards the west, the highest point of which is 995 feet. "The tests were carried out during the greater part of two days and. nights, during which time no serious ■ hitch occurred to mar the success of the operations. For a portion of the period of the tests, the top of the islands were enveloped in fog, and at times the whole islands were obscured. A complete circuit of the islands was made while on.each side of th« Great King, a straight line was steamed with the radio-beacon' station site, and the highest peak on the island in direct line. During the latter frequent-obser-vations were made for the purpose of discovering if any land interference existed, and it was found that the direction finding bearings coincided with those visually observed. During the greater portion of the time the tests were made at a range of 20 miles from the station. The maximum distance at -which teats signals were used by the direction finding, equipment on the Tutanekai was 57 miles.

"The signals transmitted by the station were received by Axvanui Radio at a distance of 77.5 nautical miles, and by merchant ships at quite . readable strength at a distance of 100 miles daylight. Sunrise effects, which it is .sometimes stated .produce interference under certain conditions, were not in evidence. On the last .morning of tho tests, owing- to fog, neither the islands nor any other land was visible. Direction -finding' tests were t.?Jcen continuously, and when the islands became visible, it was found that their true direction coincided with the bearings taken during the fog by the direction finding instrument.'

"As a result of the tests the Department is satisfied that, the principle advo-' catad under heading No. 2 can be applied in a practical manner. As in the case of a vessel's standard compass, the direction finding instrument requires to be calibrated on each vessel and have its errors tabulated. The errors may then be applied in the same manner to that in which compass errors are applied. Regarding its tabulated errors it was noted that these are fairly constant, also that the orrors are at a minimum when .the observations are' taken cither right ahead or right astern. The same may 1)0 said of bearings taken on either beam. The errors change from additive to subtractive in succeeding' quadrants when using the 360- degree system, and they follow a simple law that all observed bearings suffer deflection towards the fore and aft line of the vessel.

"Tlie Department is satisfied the radio boncori station, with its counterpart the ship's direction finder, can be considered a practical aid to navigation of special significance during thick or foggy weather."