76N6 Clam Shell Russian Low Altitude Acquisition Radar

The 76N6 Clam Shell** is a ground-based three-dimensional radar that uses frequency-modulated continuous-wave transmission for target acquisition in dense electronic countermeasures (ECM) environments. It is designed to detect and track approaching and receding low radar cross-section targets, such as cruise missiles, at very low altitudes.The fully automatic system provides target track data for the fire-control system of static SA-10a or mobile SA-10b air defense systems. Approaching and receding target velocity, range and bearing are provided, with selectable 1- or 6-degree vertical beamwidths and selectable beam polarization. The FA-51MU antenna head subsystem combines a transmit and receive antenna, separated by a shielding structure, which prevents spillover from the transmitter into the receiver. The design includes sidelobe suppression features. The doubly curved transmit and receive reflectors measure about 9 ft 6 in (2.9 m) in each dimension. The manufacturer claims world-class resolution, high rejection of clutter (100 dB) and very accurate pointing. The antenna head is mounted on a hydraulically elevated mast, which is available in two versions: the 40V6M, which is 77 ft 5 in (23.8 m) tall; or the 40V6M2/40V6MD, which is 127 ft 3 in (38.6 m) tall. The mast and antenna head are mated before elevation on a semi-trailer that is towed by a MAZ-537 tractor. A conventional rotational coupler allows the antenna head to rotate through 360 degrees. The Clam Shell transmitter, fitted in the FA-52MU transmit/receive module, produces a high-purity continuous wave signal for search operations, with imposed low frequency modulation for ranging to targets. Signal-processing enables the rejection of clutter, terrain, precipitation, high-density chaff and jamming.