Naval facilities such as the Belconnen Naval Transmitter Station, now a heritage site of Australian military engineering, proved critical for communications during World War II.
Naval communications facilities in Canberra are of major significance in Australia’s military history.
With the outbreak of World War II, the Belconnen Naval Transmitter Station, alongside HMAS Harman and the Receiver Station at Bonshaw, proved vital to the strategic deployment and operation of naval forces in the Pacific and Indian Oceans.
The heritage site had been designed as a key strategic radio communications facility on the eve of the war, and was completed in 1939.
As the most powerful low frequency (LF) transmitting station in the southern hemisphere, it communicated directly with Australian and Allied ships and submarines, and with other Allied communications stations, including those in Singapore.
Over time, the station expanded to incorporate a wide range of high frequency (HF) transmitters.
Aerial engineering
The transmitter building contains a rare 250 kW LF valve-operated transmitter that is largely original, alongside several generations of HF transmitters, controls, ancillary equipment and aerial switching exchanges.
Prior to its decommissioning, the station had 48 HF aerials of seven distinct types and three 180 m lattice towers which supported the 44 kHz LF aerial. While the buildings and its contents remain, the LF aerial towers have now been demolished and the HF aerials removed.
The three 600 ft (183.5 m) high guyed steel lattice towers from which the LF aerial was suspended were completed in June 1941 and the aerial became operational in 1942.
The galvanised steel towers were of bolted construction in three sections vertically, with guys in three directions from the top of each section. The towers were each fitted on a ball-jointed base insulator at ground level, and with winches in the lower section for hauling the aerial array into place with steel cables.
The central tower had a double drum winch while the outer towers had single drums. Slip clutches on each winch limited the tension on each cable, and hence on the array, to less than eight t.
A steel ladder with safety cage ran inside each tower adjacent to one of the vertical legs, allowing maintenance access to the full height.
Power supply and wartime operation
During World War II, the station was powered directly from the Kingston Powerhouse, also in the ACT. A steam turbo-alternator installed there in 1927 supplied a dedicated high voltage line to Belconnen some 12 km away.
A much more recent diesel alternator provided back-up power from a separate powerhouse building adjacent to the transmitter building.
Morse code operators at the station and communicating with it affectionately referred to it as ‘Bells’. It was a vital wartime communications link and a homecoming beacon for returning servicepeople.
For years spanning the Korea and Vietnam Wars it was an important part of the Australian defence communication network, and reputedly had a role in communications for the Melbourne Olympic Games.
The Navy left the site in 1995, and operation and maintenance was taken over by civilian contractors, although the Department of Defence retained ownership and responsibility for the planned disposal.
Heritage listing
The station has established significance for the role it played in World War II and the development of naval communications.
The transmitting equipment, aerials, buildings and surrounding native grasslands were entered in the Register of the National Estate (RNE) in 2002 and, following a heritage study by the University of Canberra, the facility was nominated for emergency listing on the Australian National Heritage Register.
While RNE listing did not give automatic protection, changes to Australian heritage legislation ensured Belconnen Naval Transmitter Station was included in the Commonwealth Heritage list in 2004, thus requiring its owner, the Department of Defence, to obtain approval from the Minister for the Environment and Heritage for any changes associated with its disposal.
Defence considered the LF aerial masts were a maintenance liability and sought approval for their demolition.
In 2005, the station was decommissioned as facilities were established elsewhere and the land, which was by then surrounded by Canberra suburbs, became potentially available for redevelopment.
A publicly available conservation management plan is awaited from Defence, hopefully including future use of the transmitter building to preserve the transmitting equipment.
A version of this article originally appeared in the March 2023 edition of the Engineering Heritage Australia magazine.
Keith Baker FIEAust CPEng is an electrical engineer and past chair of Engineering Heritage Australia.