For the first time the over-the-horizon radar became operational on 07 November 1971. The positive results of the tests were received for a middle-latitude route and in a relatively quiet ionosphere. The first Steel Yard OTH near Kiev began operations in 1976, and has remained on the air ever since. Transmitting on frequencies between 3.26 and 17.54 megahertz, the signal is pulse-modulated at a rate of several times a second, sounding like a woodpecker. When it first began operations, the 2 MW transmitter interfered with several communications channels, including emergency frequencies for aircraft on transoceanic flights. Subsequently the operational practice was modified so that the radar skips these critical frequencies as it moves across its operational spectrum.
Later two over-the-horizon radars of this type were built near Chernigov and Komsomolsk-na-Amure. Along with the first facility at Kiev, another Steel Yard located at Komsomolsk-na-Amur provides complementary coverage of the United States. A third smaller lower-power facility at Nikolaeyev near Odessa provides coverage of China.