Coast to Coast

Rohde & Schwarz’ SK-4105 five-kilowatt high frequency transmitters, an example of which is shown here with its cooling unit on the right, form a key part of the overhaul of New Zealand’s military HF communications infrastructure.

New Zealand will soon receive new high frequency transmitters as part of an ongoing programme to overhaul the country’s military HF communications infrastructure.

Sources close to the programme shared with Armada that shipments of new Rohde & Schwarz High Frequency (HF: three megahertz/MHz to 30MHz) transmitters to New Zealand are ongoing. A total of eleven new transmitters are being delivered. This includes ten of the company’s five-kilowatt SK-4105 transmitters along with a single ten-kilowatt SK-4110. The sources said factory acceptance tests are being performed at Rohde & Schwarz’ plants. They added that full operational capability for these new transmitters is expected to be declared in August 2023.

The transmitters will be teamed with RapidM’s RM10 modems. The modems are designed to handle US Department of Defence MIL-STD-188-110C wideband HF protocols. These provide bandwidths of between three kilohertz/KHz up to 24KHz. Data rates of up to 120 kilobits-per-second are achievable with such bandwidths.

HF Modernisation

Babcock was selected in March 2020 to replace the New Zealand Defence Force’s existing fixed HF radio infrastructure which entered service in the 1980s. A limited upgrade of that infrastructure took place in 2005, but the system has become progressively harder to sustain. The New Zealand government has invested $14.6 million (2020 values) into the naval HF modernisation. An additional annual support contract of $1.2 million was also awarded to Babcock. Assuming the new HF infrastructure has a life span of at least 30 years the entire programme could cost $57.9 million at 2022 values.

Concept of Operations

The company’s official literature says that military HF is essential to New Zealand’s armed forces to ensure that high frequency communications are provided below 60 degrees south latitude. This ensures communications can be sustained with Scott Base, Antarctica. This research facility is New Zealand’s only permanent presence on the continent. Satellite Communications (SATCOM) can be difficult or even impossible below this latitude.

Alongside providing radio communications below 60 degrees south HF is used for helicopter and Royal New Zealand Navy inshore patrol vessel communications. Such platforms can lack SATCOM capabilities. High Frequency radio is also used as a SATCOM alternative at ranges of up to 5,340 nautical miles (10,000 kilometres) from New Zealand.

The need for the new HF infrastructure was emphasised by a statement from the New Zealand government’s cabinet which warned that “(w)ithout the high frequency radio system, the defence force will be unable to communicate in a timely manner between deployed force elements and New Zealand in some circumstances. This may result in compromises to personnel safety, military operations, and an inability to perform some of the government’s mandated objectives for the defence force”.

Existing New Zealand military HF infrastructure is located near Auckland and on the lower part of the North Island at the Waiouru and Irirangi military bases. HF facilities are also located on the South Island at the Woodbourne and West Melton bases.

by Dr. Thomas Withington