From The ARRL Letter for February 28, 2019
Over-the-Horizon Radars Raising the Ire of European Monitoring Systems
The January issue of the IARU Region 1 Monitoring System (IARUMS) newsletter reports the Russian "Sunflower" coastal radar, located east of Vladivostok, is being heard at nights on 3,716 kHz and 6,860 - 7,005 kHz, as well as on several
60-meter frequencies. A Chinese wideband over-the-horizon (OTH) radar also appeared on 7,000 kHz in early January.Waveform of a Chinese OTH radar on 7 MHZ. [Photo courtesy of Wolf Hadel, DK2OM]
"Once again we have problems with short-wave radars," said the Deutscher Amateur Radio Club (DARC) Monitoring System. DARC is Germany's IARU member-society. "The Russian coastal radar 'Sunflower' transmits on almost every evening at 5,310 -
5,410 kHz. As a result, our new mini-band is useless." DARC was referring to the narrow worldwide allocation of 5,351.5 - 5,366.5 kHz to the Amateur Service on a secondary basis by World Radiocommunication Conference 2015 (WRC-15). It said the interference appears as a deep hum. The Sunflower radar employs Frequency Modulation on Pulse (FMOP) at 43 sweeps per second to detect aircraft and, over water, vessels.DARC continued, "The system is so successful that the Chinese operate several 'sunflowers' on the east coast. Chinese OTHs work almost daily in the 20-meter band. In the mornings, we can often receive them with high field strengths." DARC said the Chinese OTHs cause worse interference than the Russian radars.
DARC mentioned other OTH radars operating on 40 meters: "At the moment we have extreme problems with the 'Container' radar from Russia." IARUMS has often reported problems from this radar.
In December, IARUMS reported an OTH radar active on 21,170 kHz from the Sovereign Base areas of Akrotiri and Dhekelia, a British Overseas Territory on the island of Cyprus.
While 60 meters and 80/75 meters are shared bands, the 7,000 - 7,200 kHz segment of 40 meters is allocated exclusively to the Amateur Radio Service worldwide. Some domestic Amateur Radio HF allocations outside Region 2 (the Americas), such as 7,200 to 7,300 kHz, are either shared with other services or not available to radio amateurs. On HF allocations such as 30 and 60 meters, Amateur Radio is secondary to other users. The 20-, 17-, 15-, 12-, and 10-meter bands are exclusively available to the Amateur Radio Service worldwide.