WHAT ARE ALL THOSE WEIRD NOISES?
A LOOK AT OVER THE HORIZON RADAR

Something a little different today, but still relating to shortwave radio reception!

Over-the-horizon (OTH) radar systems represent a technological leap in long-range surveillance. They enable nations to detect and track aircraft and maritime vessels thousands of kilometres away by exploiting the reflective properties of the ionosphere. However, this capability comes at a significant cost to the global high-frequency (HF) radio community.

Shortwave listeners, amateur radio operators, and even some commercial and scientific users of the HF spectrum have increasingly found their communications disrupted by the characteristic pulsing and sweeping signals emitted by OTH radars. These systems, which transmit powerful, wideband signals across broad swaths of the 3 to 30 MHz range, are known to interfere with legitimate HF operations—often without coordination or consideration of internationally agreed-upon frequency allocations.

The problem stems from the inherent design and operation of OTH radar systems. Unlike narrowband communications used by most HF users, OTH radars use frequency-modulated continuous wave (FMCW) or pulse compression techniques that occupy bandwidths of up to 50 kHz or more per sweep, sometimes scanning rapidly across hundreds of kilohertz. This broad spectral footprint, combined with the high output power necessary for long-range detection, often causes unintentional interference.

For hams and SWLs, this interference manifests as sharp, periodic pulses, buzzing tones, or sweeping noises—particularly disruptive during contest weekends, emergency communication nets, or critical propagation conditions. While some radar systems attempt to avoid amateur bands, this is not universally observed, and real-time frequency agility can still place emissions where they are least expected.

Moreover, OTH radar interference is notoriously difficult to predict or mitigate at the user level. Because these systems are designed to exploit the same ionospheric propagation characteristics that make amateur radio and international shortwave broadcasting so effective for long-distance communication, their signals can propagate globally, rendering local filtering largely ineffective. This is compounded by the lack of transparency surrounding the operation of military-grade radars; many systems operate under national security exemptions and are not subject to the same spectrum coordination protocols required of civilian users. Consequently, hobbyists and licensed HF operators are left with limited recourse when persistent radar interference disrupts their activities—a growing concern as more nations invest in HF-based OTH radar technologies.

One of the most recognisable and historically infamous examples of OTH radar interference was the Russian “Woodpecker”, officially known as the Duga radar, which operated from the late 1970s through the 1980s. Its repetitive tapping noise—resembling a woodpecker’s pecking—could be heard across large portions of the shortwave spectrum, causing widespread disruption to amateur radio operators, broadcasters, and even early digital communication systems. The Woodpecker transmitted powerful signals between 7 and 19 MHz, often with no regard for international band plans.

In today’s HF landscape, modern successors to this legacy include Russia’s Container radar (“Konteinër” or “Контейнер” in Russian), China’s OTH-B, and Australia’s JORN, each employing sophisticated frequency-hopping techniques and sweeping wide bandwidths that remain audible to SWLs and amateurs alike. These modern systems may be less intrusive in design. However, their presence is still regularly observed on waterfall displays, often showing up as broad, sweeping, or chirping signals that momentarily—or persistently—blank out segments of the amateur HF spectrum.

So what is JORN?

The Jindalee Operational Radar Network (JORN) is an advanced over-the-horizon radar (OTHR) system developed and operated by Australia. It is one of the world’s most sophisticated and powerful surveillance radar networks, capable of detecting and tracking aircraft, ships, and other objects thousands of kilometres away. JORN provides Australia with critical early warning capabilities and plays a key role in national defence, border security, and environmental monitoring.

Jindalee is an Aboriginal word for a place [the] eye cannot see, or somewhere beyond where the eye can see, like over the horizon.

JORN has a range of 3,000 to 5,500 kilometres, covering much of Southeast Asia, the Indian Ocean, and the South Pacific. It currently consists of three main radar sites: Longreach, Queensland; Laverton, Western Australia; and Alice Springs, Northern Territory. These sites are networked and controlled from a central facility at the Royal Australian Air Force (RAAF) Base Edinburgh in South Australia. The network also includes seven transponders, and twelve vertical ionosondes (radar for reporting on current propagation conditions) distributed around Australia and its territories.

JORN relies on cutting-edge digital signal processing and artificial intelligence to analyse vast amounts of radar data, distinguishing between hostile threats, civilian aircraft, and natural phenomena. The system is highly automated and requires relatively few personnel to operate, reducing costs while maintaining a constant surveillance capability.

From the national defence and security perspective, JORN provides early warning of potential threats, including military aircraft, naval movements, and missile launches. It is a crucial component of Australia’s Integrated Air and Missile Defence Strategy. The system helps detect illegal fishing, smuggling, and unauthorised vessel movements within Australia’s Exclusive Economic Zone (EEZ).

In addition, it supports border security agencies in monitoring refugee movements and maritime incursions. JORN enhances Australia’s intelligence-sharing capabilities with key allies like the United States, the UK, and Five Eyes partners. It contributes to regional stability by providing long-range surveillance over the Indo-Pacific. JORN tracks weather patterns, space debris, and ionospheric activity, which is valuable for scientific research and space operations.

JORN is often compared to similar OTHR systems operated by the United States, Russia, and China. Due to its sophisticated algorithms and long-range tracking capabilities, it is regarded as one of the most advanced and reliable.

Does JORN have an impact on shortwave listening and amateur radio activities?

Like other HF OTHR systems, the Jindalee Operational Radar Network does generate interference, but steps are taken to minimise its impact. Because JORN operates in the 3 MHz to 30 MHz range, it overlaps with frequencies used for amateur radio, maritime communications, aeronautical systems, and international broadcasting.

JORN employs adaptive frequency selection and hopping to avoid prolonged interference on a single channel. The system scans for the least congested HF frequencies before transmitting, reducing the likelihood of disrupting existing communications. This approach helps mitigate, but not eliminate, interference.

The Australian Communications and Media Authority (ACMA) works with Defense agencies and HF spectrum users to manage interference issues. JORN is classified as a protected priority system in Australia’s spectrum management plan, meaning some civilian HF operations must adjust to avoid conflicts. The system operates primarily in military-assigned HF bands, but incidental interference can still occur in shared bands.

Some ham radio operators and shortwave listeners have reported strong JORN signals causing interference, particularly in the 20-meter (14 MHz) and 40-meter (7 MHz) bands. International broadcasters have sometimes encountered signal disruptions in HF bands due to JORN’s transmissions. Since JORN relies on ionospheric reflection, its frequency usage changes based on solar activity, time of day, and seasons. This can cause interference in unexpected HF bands at different times.

How does JORN compare with other OTHR systems?

The Jindalee Operational Radar Network is one of the world’s most advanced over-the-horizon radar (OTHR) systems, but it is not the only one. When compared with other systems:

JORN has the longest effective detection range (~5,500 km), giving Australia deep surveillance into the Indo-Pacific region.
Russia’s OTH radars (Duga & Container) focus on missile detection and military surveillance, whereas JORN is multi-role.
The U.S. ROTHR (Relocatable Over-the-Horizon Radar) is primarily used for maritime and anti-drug operations, whereas JORN is focused on air and sea defence.
China’s OTH-B radar is a high-power system used for early missile warning, but its full capabilities are classified.
France’s NOSTRADAMUS radar is an experimental HF radar with adaptive digital processing, but it is not as advanced as JORN.

JORN features an AI-driven frequency selection system, which dynamically adjusts to ionospheric conditions. Other radars, like Russia’s Container and China’s OTH-B, rely on more traditional HF radar techniques. Compared to the old Russian “Woodpecker” (Duga) radar, which caused massive HF interference globally, JORN is designed to minimise disruption. It uses advanced digital signal processing (DSP) and real-time frequency hopping to avoid interfering with civilian and military HF communications.

JORN has an advanced real-time ionospheric sounding system, allowing it to adjust its frequency and transmission power in real-time. This makes it more effective in variable space weather conditions than older systems like the U.S. ROTHR or Russia’s Container radar.

JORN is not just a military radar; it is also used for border security (detecting unauthorised maritime entries), maritime surveillance (tracking illegal fishing, smuggling, and naval activity), and disaster response (helping coordinate rescue efforts in remote oceanic regions).

JORN’s Limitations

JORN is optimised for air and maritime surveillance but is not designed to detect land-based targets well. Russia’s Container radar has better land surveillance capabilities, making it more effective for border monitoring.
Unlike Russia’s OTH radars, which are integrated into their early missile warning systems, JORN is not currently directly linked to missile defence networks.
China’s OTH-B radar is believed to be tightly integrated with its military, allowing it to assist in missile strike targeting—something JORN does not do.
The U.S. ROTHR is relocatable (it can be moved and deployed elsewhere).
JORN is a fixed installation, which is not as flexible for temporary or emergency deployments.

Future Developments: JORN Phase 6 vs. Other OTH Radars

Significant upgrades to JORN are underway in what is known as JORN Phase 6. These include AI-driven radar processing and frequency selection, integration with space weather forecasting, enhanced tracking of hypersonic missiles, and an extended range beyond 6000 kilometres.

For other global radar systems, China is rapidly improving its OTH-B radar, integrating it into military operations. Russia’s OTH radar remains outdated in some areas but is still effective for missile warning. The U.S. ROTHR is still operational but lacks the range and adaptability of JORN.

Canada’s interest in Australia’s JORN

Canada has recently decided to acquire Australia’s Jindalee Operational Radar Network (JORN) to enhance its Arctic surveillance capabilities and strengthen national defence. This decision aligns with Canada’s broader efforts to modernise the North American Aerospace Defense Command (NORAD) infrastructure and assert sovereignty over its northern territories.

The JORN system allows for the detection of air and maritime threats at distances up to 3,000 kilometres. By bouncing radar signals off the ionosphere, JORN provides early warning and situational awareness far beyond the line of sight, making it particularly suited for monitoring the vast and remote Arctic region. Canadian Prime Minister Mark Carney emphasised that this acquisition would enable Canada to “detect and respond to both air and maritime threats over our Arctic both faster and from further away,” thereby enhancing national security.

The procurement of JORN represents a significant milestone in defence collaboration between Canada and Australia. This move reflects Canada’s strategic initiative to diversify its defence partnerships and capabilities amid evolving geopolitical dynamics.

The deal comes as Canada faces pressure from the US to increase defence spending. For months, Australian officials had discussed selling JORN to the U.S., but uncertainty arose due to the Musk-led “DOGE” audit of Pentagon spending. Canada announced plans to purchase the system from BAE Systems Australia for more than CAD 6 billion ($4 billion).

The sale of the JORN radar system represents the largest defence export in Australia’s history. Amid ongoing U.S. trade tensions, Prime Minister Anthony Albanese underscored the strategic need for Australia to diversify its trade partnerships. The United States had previously shown interest in acquiring JORN for possible deployment along its West Coast. According to an Australian official, the original expectation was that the U.S. would be the first international customer, with Canada to follow. This made Canada’s move to purchase the system ahead of the U.S. surprising and diplomatically significant.

* * * *

So, there you have it. You now know more about Over-the-Horizon-Radar systems, Australia’s JORN system, its strengths and weaknesses and why Canada is negotiating its purchase. Next time you hear strange noises – pops, pulses and swishes – you can bet that it’s probably one of the world’s radar systems in action.

73 and good DX,

Rob Wagner VK3BVW

Current local time in
Mount Evelyn, Australia

CLICK HERE for VK3BVW Live Stream (Clublog)

QRZ callsign lookup:

Search This Blog

Mount Evelyn DX Report