A RADAR (English acronym of Radio Detection And Ranging ) is a system that uses electromagnetic waves to measure different parameters of objects, whether static or mobile, such as their speed , altitude , direction, size, etc. Its operation is based on the emission of a radio impulse, which is reflected by the target and is typically — but not always — received at the same position of the transmitter. From this “echo” a large amount of information can be extracted.

Antenna of the well-known (already silent) RUS OTHR Duga (“Woodpecker”).Source


  • OTHR : Acronym for Over The Horizon Radar . This is a type of radar system capable of detecting objects at very long distances, typically hundreds to thousands of kilometers, beyond the radar horizon, which is the range limit for ordinary radar.
  • BW: abbreviation for English Bandwidth . Indicates the bandwidth required for a transmission mode. Both on screen and in classic reception, when receiving radars we will sometimes notice that the bandwidth of their signals is much higher than that indicated in BW . This is due to the enormous amount of power used in transmission, which generates spurious, exceeding the necessary bandwidth.
  • K0E: indicates, in kHz, the bandwidth of a signal according to the ITU nomenclature, in which the E indicates estimated , referring to the fact that the bandwidth measurement (even if the data offered is correct) is not has been performed according to ITU requirements.
  • sps: abbreviation of the English sweeps per second , referring to the rate of sweeps per second with which the radar emits.
  • BD: abbreviation for Burst Duration , used when a radar emits bursts . Refers to the duration of the burst.
  • BRIBurst Repetition Interval ; repetition interval between bursts
  • cacirca , approximately.

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OTHR Contayner

Modulation: FMOP.
Necessary BW = 12 kHz (may appear to use a much larger BW due to spurious and high power used in its transmissions).
Sweep rate: 40 sweeps per second (sps).
RX: 40m., 30m, 20m, 17m, 15m and 12 m bands
It’s been received sending up to 5 simultaneous transmissions on the same band



ITU: G. British radar located at the United Kingdom’s Sovereign Base Area in Cyprus.
Modulation: FMCW
It mostly uses a bandwidth of 20 kHz, but seldom it uses other BW, like 40 kHz. It has been very rarely received with BW = 80 kHz.
Usual weep rates are 50 or 25 sps, but it can be sometimes receiving using 12.5 sps.
RX: 17, 15, 12, 10m. Very rarely on 30m.
It’s been received sending up to 3 simultaneous transmissions on the same band




Iranian OTHR

Modulation: AMOP.
It uses a bandwidth of ca. 45 kHz.
It transmits bursts, usually alternating two sweep rates, although it can sometimes be received sending bursts of the same sweep rate.
The most usual alternated sweep rates are 150 sps and 313 sps, but it can be heard alternating 226 sps and 333 sps bursts, or 307 sps and 870 sps bursts.
RX: 10 m band
It’s been received sending up to 3 simultaneous transmissions on this band.
It can often be heard at 28860 kHz CF.





Here we describe and show the different Chinese Over The Horizon radars most usually received in the amateur radio bands.

CHN OTHR “Foghorn”

They have been so nicknamed because of their characteristic sound, similar to a ship’s foghorn. Short bursts. The duration time of the bursts (BD) and time between bursts (BRI) may vary.
Modulation: FMCW.
Bandwidth: 10 kHz.
The sweep rates most usually used on their transmissions are 66.66 sweeps per second (sps, Sweep rate: 66.66 sweeps per second (sps), and 50 sps. They can also be received using a sweep rate of 42 sps. They are seldom observed using 83.3 sps and other sweep rates.
RX: 40, 30, 20, 17, 15 and 12 meter bands

CHN OTHR Foghorn burst



CHN OTHR BW = 10K0E, 50 sps

Modulation: FMCW
Bandwidth: 10 kHz
Sweep rate: 50 sweeps per second (sps)
RX: 20, 17 and 15 meter bands

CHN OTHR 10K0E 50 sps

CHN OTHR BW = 40 kHz, 10 sps

Modulation: FMCW
Bandwidth: 40 kHz
Sweep rate: 10 sps
RX: 20 and 15 m bands

CHN OTHR 40K0E 10 sps

CHN OTHR BW = 40 kHz, 20 sps

Modulation: FMCW
Bandwidth: 40 kHz
Sweep rate: 20 sps
RX: 20 m band. Rare!

CHN OTHR BW 40K0E 20 sps

CHN Wideband OTHR

Modulation: FMCW
Transmission: continuous, or bursts (BD ca 50 sec; BRI ca 90 sec; both may vary. Sometimes there is no time lapse between bursts: then, a change of center frequency is noted
Bandwidth: 160 kHz
Sweep rate: 10 sps
RX: 40, 20, 17, 15 and 12 m bands

CHN OTHR BW = 10K0E, 66.66 sps

Modulation: FMCW
Bandwidth: 10 kHz.
Sweep rate: 66.66 sps
Same as the CHN “Foghorn” 66.66 sps, but sending a continuous TX instead of short bursts.
RX: 20 m band. Rare!

CHN OTHR 10K0E 66.66 sps


JORN = Jindalee Operational Radar Network
Modulation: FMCW
Bandwidth: 10 kHz (Sometimes observed using 12 kHz)
Sweep rate: 7 sps
RX: 30 m band
These OTHR uses two different modes of transmission:

  • Short bursts with short intro tone; same sweeprate — 7 sps — per burst
  • Short bursts with short intro tone; different sweep rate — various — per burst. This mode is very rarely observed in the 30 m band


SuperDARN = Super Auroral Dual Radar Network
ITU: TX facilities in several countries around the world
BW ca 5 kHz
Bursts of various duration
RX: 20 m band

SuperDARN radar


CODAR = Coastal Ocean Dynamics Applications Radar

These radars are used to conduct oceanographic research.

Bandwidth: may vary
Sweep rate: usually low (may vary)

XXX Radars

XXX is the ITU’s classification of emissions code corresponding to “unknown type of modulation”.

Here are shown some radar transmissions whose transmission modes and / or ITU is unknown, and which are very seldom observed in the amateur bands.

XXX radar BW = 60 kHz, 92 sps

Moduation: XXX
ITU: unknown
Bandwidth: ca 60 kHz
Sweep rate: 86 sps
RX: Very rare!

Radar XXX  BW 60K0E 86 sps

XXX radar BW = 10K0E, 100 sps

Modulation: XXX
ITU: XXX (possibly G, UK SBA, Cyprus??)
Bandwidth: 10 kHz.
Sweep rate: 100 sps
RX: Very rare!

Radar XXX BW 10K0E 100 sps

XXX radar BW = 4 kHz, 25 sps

Modulation: XXX
ITU: unknown (Possibly G; UK SBA, Cyprus??)
Bandwidth: 4 kHz
Sweep rate: 25 sps
RX: Very rare!

Radar XXX BW 4K0E 25 sps

Print This Page Updated on April 11, 2024

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