Tag Archives: OTH

Looking at HF OTH RADAR

Many thanks to SWLing Post contributor, Trevor, who shares this link to a blog post from Daniel Estevez describing the characteristics of HF OTH RADAR:

Most amateur operators are familiar with over-the-horizon radars in the HF bands. They sometimes pop up in the Amateur bands, rendering several tens of kilohertzs unusable. Inspired by Balint Seeber’s talk in GRCon16, I’ve decided to learn more about radars. Here I look at a typical OTH radar, presumably of Russian origin. It was recorded at my station around 20:00UTC on 8 December at a frequency around 6860kHz. This radar sometimes appears inside the 40m Amateur band as well.

Above this post you can see a waterfall plot of the radar signal. It’s the wide red signal. It is 15kHz wide and pretty strong, but severely affected by frequency-selective fading. Looking at the IQ recording in Audacity, it is clear that the radar uses pulses with a 50Hz repetition rate. This explains the characteristic sound of this radar when received with a conventional SSB radio. It sounds similar to AC hum (here in Europe, of course).

Continue reading on Daniel’s blog…

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Hearing Ghadir: Iran’s Sepehr Phased Radar System


In response to Andrea’s UVB-76 recording, SWLing Post contributor, Mehdi, comments:

Thomas, another signal which may sound mysterious:

Iran’s OTH Radar, named “Ghadir”; part of Iran’s Sepehr Phased Radar System.

They’d polluted the 10-meter band [in the past]; now they transmit on 26MHZ. (See spectrum in screen capture above.)

Sound: https://clyp.it/ldpxab2a

By the way, here’s my recording of UVB-76:

Many thanks for sharing those audio clips, Mehdi! Now I’ll know what Ghadir sounds like, should I hear it on the bands.

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