18 March 2025
Work is under way to overhaul a kilometres-wide and 300-metre-tall transmitter array in the remote West Australian town of Exmouth.
The Naval Communication Station Harold E Holt is a US-Australian very-low-frequency transmitting station capable of sending messages to submarines deep underwater.
In a town where the mercury reaches the high 40s, Australian and American subject-matter experts will collaborate with contractors to overcome extreme conditions and isolation, according to Navy Intelligence and Information Warfare’s Lieutenant Commander Heath Crawford.
Thirteen towers support hundreds of tons of wire antennae, criss-crossing like a spider’s web to create a giant geometric pattern more than 400 hectares in area, hundreds of metres in the sky.
Tower Zero, once the tallest structure in the Southern Hemisphere at 387 metres, sits in the middle of the array and above the helix house.
Inside looks like something lifted from the pages of a Jules Verne novel, with copper antenna tuning equipment supported by more than 100 tonnes of wood.
Almost everything inside the helix house is made of a special resin-infused wood composite, even the nuts and bolts.
High electromagnetic fields heat metal to the point where it can melt through wood.
“It’s a Cold War artefact but physics don’t change,” Lieutenant Commander Crawford said.
“I don't think anyone who steps in fully understands the system’s uniqueness because it is so different to anything anyone’s seen before.”
It is the first major upgrade to the helix house since the US Navy commissioned and opened the facility in 1967.
As a way of shoring up global coverage for its fleet of nuclear submarines, the US looked to expand its network of very-low-frequency transmitters into Australia during the height of the Cold War.
'It’s a Cold War artefact but physics don’t change.'
The nearby town of Exmouth was established to support the station along with hundreds of US personnel and their families.
In 1992, the US Navy passed command to the Royal Australian Navy. The station is now operated and maintained by Defence.
The array towers are an ever-present symbol of the town’s origins. However, the region’s military history stretches back to World War 2, when the North-West Cape was home to a US submarine and communications facility.
It was the launch pad for Z Special Unit’s behind-enemy-lines raids on Japanese forces in Singapore, including the loss of 23 allied commandos during Operation Rimau.
The operation’s original planning map now hangs in the communication station’s main office.
Sharon Jones, who works for the Maritime and Strategic Communications SPO at Harold E Holt, moved to Exmouth before the Americans handed over control.
She remembered a time when backyard fences were discouraged and American hospitality was the talk of the town.
“You didn’t have to follow the footpaths, you could just walk through people’s backyards,” Mrs Jones said.
“The 4th of July and New Year’s Eve were big open things with celebrations everywhere and a pipe band would lead people from one place to another.
"People thought that when the Americans left, the town wouldn't exist.
“We’ve gone through so many changes; Exmouth has become more of a tourism town recently.”
But despite the changing nature of Exmouth, Lieutenant Commander Crawford said the transmitter remained an important capability into the future.
Construction will commence on a rolling schedule in order to maintain assured communications with allied submarines operating in the region.
