The remaining built elements of the Royal Australian Navy (RAN) Station 9, a World War II-era indicator loop and photo-electric (PE) beam monitoring complex, are located in Myrtletown Reserve, at the end of Gannon Road near Pinkenba. The concrete control hut and concrete generator hut still stand at the southeast corner of the reserve, along with a number of concrete slabs from the quarters and mess building.
The site of RAN Station 9, located on the northern bank of Boggy Creek where it joins the Brisbane River, was gazetted as a Reserve for Recreation in 1885. A Reserve for Landing was located just to the north, and both reserves were initially under the control of the Toombul Divisional Board. In January 1925 both reserves, now jointly known as Myrtletown Reserve (3.55 hectares), were transferred to the Brisbane City Council, which remains the trustee. The Myrtletown area, formerly an agricultural district, is now an industrial zone, with large undeveloped blocks and few houses. Most residents left due to the construction of Brisbane Airport nearby (opened in 1988), and the local school closed in 1971.
During World War II the coastal artillery defences of Moreton Bay were upgraded. These included Fort Lytton (1880 - 1881) on the southern side of the Brisbane River's mouth and Fort Cowan Cowan (late 1930s), on the west side of Moreton Island. Fort Bribie, at the northeast tip of Bribie Island, was established in 1939 after Germany's invasion of Poland plunged the world into war. Japan's entry into the war on the 7th of December 1941, and the consequent perceived invasion threat to Australia, led to a further expansion of Moreton Bay's defences. Fort Bribie upgraded its two 6" gun emplacements in early 1942, and in June 1942, the Commander of the Allied Naval Forces in the Southwest Pacific Area requested as a matter of high priority that Moreton Bay be developed as a naval operating base. Later that year two American 155mm field guns were emplaced on Panama Mounts at Skirmish Point, at the south end of Bribie Island. In 1943 a similar battery was built at Rous, on the east side of Moreton Island.
The major access route into the Brisbane River was the Northwest Channel, which ran from near Caloundra across the bay in a southeast direction (east of Bribie Island and towards Moreton Island) and then southwest towards the mouth of the Brisbane River, forming a Z-shaped route. This dictated the ideal positions for coastal artillery batteries, with the most effective sites for guns being the closest points to the channel bends. However, Rous battery was designed to deter ships from shelling targets within Moreton Bay from the ocean side of Moreton Island.
During World War II Moreton Bay was also protected by RAN stations numbers 1 through 10. RAN 1 was a Port War Signal Station at Wickham Point, Caloundra (not extant), and RAN 2 was a Controlled Mining and Guard Loop Station which was initially located at Fort Bribie (extant), before it was moved to Tangalooma on Moreton island in 1943 (not extant). RAN 3 was a Controlled Mining and Guard Loop Station at Cowan Cowan, and RAN 4 was the Indicator Loop and Harbour Defence ASDIC (anti-submarine detection sonar) Station at Woorim, on Bribie Island (extant). RAN 5 was the Combined Training Centre (Naval Wing), at Toorbul; RAN 6 was an Advanced Fairmile Base (AFMB) at Bongaree, Bribie Island; and RAN 7 was an Indicator Loop and Harbour Defence ASDIC Station at Bulwer on Moreton Island (extant). On the Brisbane River, RAN 8 was the Boom Defence Facility, an Anti-submarine Boom across the Brisbane River between Lytton and Bulwer Island (not extant); RAN 9 was the Indicator Loop and Photo-electric Beam Station, Myrtletown (extant); and RAN 10 was a Naval Store at Pinkenba (status unknown).
Indicator loops were used to detect the presence of any submerged submarines. An indicator loop relies on the production of an induced current in a stationary loop of wire when a magnet moves overhead. Even if wiped or degaussed, submarines still have sufficient magnetism to produce a small current in a loop. The technology was developed by the British Royal Navy at HMS Osprey (Portland Naval Base) from 1915. If an indicator loop showed the presence of a vessel the two possibilities were 'sub' or 'non-sub'. If no ship could be observed on the water, it was obviously a submarine, and a vessel could be despatched to drop depth charges.
Alternatively, if an indicator loop was located next to a controlled minefield, in which the mines were connected by electrical cable back to a mine control hut on shore, the mines could be detonated manually if a submarine was detected. It had to be an enemy submarine as friendly submarines always entered port surfaced. The controlled mines in Moreton Bay were accompanied by 'guard' indicator loops and mine loops. When a submarine was detected by the guard loop, the operator would wait until there was also a galvanometer 'swing' on the mine loop and then the mines would be detonated by sending a current down the mine loop.
RAN Station 9 was designed to detect any Japanese submarines or surface vessels attempting to navigate up the Brisbane River. By 1942, the navy had become aware of recent developments by Japan, Germany and Italy in the manufacture and use of miniature submarines and human torpedoes. Existing indicator loop systems had legs set at a 200 yard spacing which was fine for large submarines but useless for the miniatures. By September 1942 the RAN decided to lay a miniature indicator loop across the mouth of the Brisbane River.
The indicator loop cables were laid in a miniature indicator loop pattern with legs 40 yards apart, from RAN Station 9 to Fisherman Islands. If a submerged submarine was detected by RAN Station 9 a signal would be transmitted to RAN Station 8, the Boom Defence Facility at Fort Lytton, to raise the boom cable. HMAS Kinchela was permanently moored in the Brisbane River as part of this Boom Defence system. The indicator loop was completed by HMAS Bangalow by early March 1943.
The indicator loop was supplemented with a photo-electric beam above the water, to detect the presence of surface vessels entering the Brisbane River. RAN Station 9 in Brisbane was one of only three PE beam installations built in Australia during World War II, the others being between South Head and Middle Head in Sydney, and between Point Lonsdale and Point Nepean at Port Phillip in Melbourne. Lieutenant Colonel Buckland of the Australian Army was responsible for the installation of all three.
The PE Beam equipment consisted of a transmitter on the Fisherman Islands side of the Brisbane River housed in a concrete hut, at a bearing of 68 degrees and 25 minutes from the receiver at Myrtletown. The current status of the transmitting hut is unknown, due to the development of wharfage facilities around that location. The PE beam transmitter consisted of a power valve that transmitted in the visible and infrared wavelengths. An infrared screen blocked out the visible light so that it couldn't be seen from the outside. The beam from the transmitter was directed at the reflector (a 90 cm parabolic mirror) in the control hut at Myrtletown, which focussed the rays to a pin point on the cathode of the PE cell.
Breaking the beam closed a contactor on to an 80 Volt DC supply and connected it in parallel with a service contactor. While the beam was in normal operation, a loudspeaker gave a buzzing note. When the beam was broken, the speaker reproduced the clicking of the receiver relay. An alarm buzzer also sounded and a flashing red light came on actuated by the relay. During this interruption, another contactor closed and a sentry (searchlight) was exposed across the river, on a bearing a few degrees inside the line of the infrared PE beam. The service contactor switch for the searchlight was then closed by the switchman, who carried out a quick search of the area; the control panel contactor being immediately reset by pressing a button on the control panel. Resetting stopped the alarm buzzer, flashing light and the clicking in the loudspeaker, leaving the apparatus ready to give another signature immediately.
The PE beam was completed in September 1943 and on 23 October 1943 the first trial of the beam was undertaken. RAN Station 9 commenced operation in January 1944, after a construction cost of £3337. Lieutenant Joe Duggan was the Officer in Charge.
RAN Station 9 never detected any Japanese intruders, although submarines had been sighted east of Stradbroke Island (March 1942) and off Moreton Island (June 1942), and on 14 May 1943 the hospital ship Centaur was struck by a torpedo and sunk off the Brisbane coastline. The last attack to occur in the approaches to the Port of Brisbane took place on 4 June 1943 off Cape Moreton, when a Japanese submarine fired on the American ship MV Edward Chambers. The indicator loop in the Brisbane River was removed in June 1945.
A 1946 aerial photograph of the RAN Station 9 facility shows that the quarters and mess building were located to the north of the control and generator huts (at the location of the existing concrete slabs and brick cisterns). Two outhouses were located northwest of the existing generator hut. The larger of the two remaining structures, the control hut, accommodated the indicator loop and PE beam instrumentation and was where the loop cables terminated. The smaller building housed the generator. The living quarters for officers and ordinary ranks were separated by a mess area.
Source: Queensland Heritage Register.
