Jindalee Operational Radar Network (JORN)

Jindalee Operational Radar Network
(JORN)
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
ACF	—
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 radar that can use a similar transmission mode as JORN. ^[1] It may be difficult to tell that and JORN apart.

Samples[edit]

The following samples are USBUpper Side Band Modulation (Radio, referring to reception and modulation mode)Universal Serial Bus (Computer, referring to USB Ports and cables) with narrow and wide bandwidths unless described otherwise. Transmission bandwidth was 10 kHzKiloHertz (kHz) 10^3 Hz in most cases as it is the most common bandwidth used by this radar. Wide USBUpper Side Band Modulation (Radio, referring to reception and modulation mode)Universal Serial Bus (Computer, referring to USB Ports and cables) sample covers the entire transmission, narrow USBUpper Side Band Modulation (Radio, referring to reception and modulation mode)Universal Serial Bus (Computer, referring to USB Ports and cables) sample is about 2.8 kHzKiloHertz (kHz) 10^3 Hz wide.


Single burst, modulated intro tone	Single burst, short and plain intro tone	Two bursts, modulated intro tone	Single burst, AMAmplitude Modulation and FMFrequency Modulation samples. Note intro tone modulation in AMAmplitude Modulation.


Repeating bursts, slow sweep rates, modulated intro tone	Repeating bursts, short and plain intro tone	Repeating bursts, short intro, varying strength, possible beam steering	Repeating bursts, faster sweep rate (67 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz).), about 8 kHzKiloHertz (kHz) 10^3 Hz bandwidth


Three bursts with 12 kHzKiloHertz (kHz) 10^3 Hz bandwidth, modulated intro tone	Two bursts with 8 kHzKiloHertz (kHz) 10^3 Hz bandwidth, modulated intro tone

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

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

Video Examples[edit]

Additional Links[edit]

Additional Images[edit]


JORN Coverage in Australia. 1RSU = Alice Springs. JORN repeating its bursts very often. Slightly different sweep rate each burst, corresponding to different ranges. JORN waterfall images, from IARUMS report JORN seen on 5440kHz and 7995kHz JORN seen from an unknown location in Australia. JORN active on three frequencies near 25 MHzMegaHertz (MHz) 10^6 Hz HFDL data transmissions (left) and JORN radar bursts (right) JORN standard transmissions and sounder mode hopping from 25 MHzMegaHertz (MHz) 10^6 Hz to 24 MHzMegaHertz (MHz) 10^6 Hz to 23 MHzMegaHertz (MHz) 10^6 Hz Two JORN sounder transmissions on nearby frequencies 16x64 sounder, complete transmission 16x64 sounder pauses and changes frequency during transmission JORN 16x64 and standard sounder modes on the same frequency "14-sounder" variant, complete transmission