Jindalee Operational Radar Network (JORN)

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Jindalee Operational Radar Network
Frequencies 10.153 MHz,22.95 MHz,5.7 MHz,32 MHz,33 MHz,8.992 MHz
Frequency Range 5.7 MHz - 33 MHz
Mode USB
Modulation FMCW
Emission Designator
Bandwidth 10 kHz,3 kHz,12 kHz,15 kHz,30 kHz,35 kHz,40 kHz,50 kHz,60 kHz
Location Australia
Short Description JORN is an Australian OTHR system that operates uniquely in that it's radar bursts include an intro tone before the burst.
I/Q Raw Recording
Audio Sample

JORN is an Australian over-the-horizon radar system. It transmits an FMCW signal in bursts, and each burst has an intro tone. Sweep rates can vary over a wide range. The most common bandwidth is 10 kHzKiloHertz (kHz) 10^3 Hz but other bandwidths such as 3 kHzKiloHertz (kHz) 10^3 Hz or 15 kHzKiloHertz (kHz) 10^3 Hz may be used. The sounder modes (see below) use many different bandwidths. Transmission frequency can vary from 5.7 MHzMegaHertz (MHz) 10^6 Hz to 33 MHzMegaHertz (MHz) 10^6 Hz or even lower or higher.

The intro tone can be very short and plain, or it can be slightly longer and have noticeable modulation. It is not known why different intro tones are used. The radar can also transmit without an intro tone, but it's uncommon, see the video example below. The purpose of the intro tone has not been confirmed, but according to a post in the UDXF group, it is used to check impedance matching between the transmitters and the antennas. If impedance matching is not correct, transmission would be aborted.

JORN's OTHOver The Horizon (very long range) network is comprised of three radar sites. One at Alice Springs (1RSU), the first OTHOver The Horizon (very long range) to be built in Australia, and two other ones at Laverton and Longreach.

JORN can be confused with the Relocatable Over-the-Horizon Radar (ROTHR) of USA, but can be usually differentiated by its different bandwidth and different intro tone. The waterfall appearance of HFDL also resembles JORN but the former can be differentiated by its narrow bandwidth and entirely different sound when demodulated.

There may be a Chinese OTHOver The Horizon (very long range) radar that can use a similar transmission mode as JORN. [1] It may be difficult to tell that and JORN apart.


WIP WIP WIP samples coming

Sounder mode[edit]

These are samples of a sounder mode that is believed to originate from JORN. The purpose of this mode has not been confirmed but it may be used for ionospheric sounding to check ionospheric conditions so that optimal frequency can be chosen for the main radar transmission.

The sounder mode typically uses slow sweep rates of less than 10 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz). and bandwidth from 3 kHzKiloHertz (kHz) 10^3 Hz up to 50...60 kHzKiloHertz (kHz) 10^3 Hz. Either 64 or 128 sweeps are usually transmitted. Transmissions often happen on or near integer MHzMegaHertz (MHz) 10^6 Hz frequencies, and after one transmission is complete, frequency is typically changed by 1 MHzMegaHertz (MHz) 10^6 Hz downwards or sometimes upwards. Unlike some other OTHOver The Horizon (very long range) radars, this sounder mode often seems to avoid frequencies that are in use. This behavior is seen when the sounder chooses a frequency that is slightly above or below the expected integer MHzMegaHertz (MHz) 10^6 Hz value.

The samples in the following examples are in USBUpper Side Band Modulation (Radio, referring to reception and modulation mode)Universal Serial Bus (Computer, referring to USB Ports and cables) mode, with narrow and wide bandwidths.

7 sweeps/sec, 12 kHzKiloHertz (kHz) 10^3 Hz wide,
128 sweeps
7 sweeps/sec, 11.5 kHzKiloHertz (kHz) 10^3 Hz wide,
128 sweeps, short intro tone
4 sweeps/sec, 30 kHzKiloHertz (kHz) 10^3 Hz wide,
64 sweeps, modulated intro tone
4 sweeps/sec, 30 kHzKiloHertz (kHz) 10^3 Hz wide,
64 sweeps, short intro tone

JORN sounder 12kHz 7Hz 128sweeps 1.png

JORN sounder 11kHz 7Hz 128sweeps short intro 1.png

JORN sounder 30kHz 4Hz 64sweeps 1.png

JORN sounder 30kHz 4Hz 64sweeps short intro 1.png

16x64 sounder mode[edit]

The 16x64 sounder is a special mode used by JORN. In this mode, the radar transmits 16 bursts, each with 64 FMCW sweeps, with sweep rate decreasing after each burst. Like the basic sounder mode, this mode also typically hops in 1 MHzMegaHertz (MHz) 10^6 Hz steps downwards. Bandwidth of this mode is usually 3 kHzKiloHertz (kHz) 10^3 Hz.

The purpose of the 16x64 sounder mode is not known but it has been suggested that it's used to check ionospheric conditions. It has also been called "searchlight mode".

A 14-burst variant with pauses between bursts and changes in sweep count has been observed in 2024.

16x64 sounder, 3 kHzKiloHertz (kHz) 10^3 Hz BW "14-sounder" variant, 3 kHzKiloHertz (kHz) 10^3 Hz BW
JORN 16x64 sounder 1.png
JORN 14-sounder 1.png

Video Examples[edit]

Additional Links[edit]

Additional Images[edit]


  1. https://www.hfunderground.com/board/index.php/topic,76456.msg252627.html#msg252627