RELEDOP - A FULL-SCALE ANTENNA PATTERN MEASUREMENT SYSTEM FOR HIGH-POWERED HF TRANSMITTING ANTENNAS

A system is presented that utilizes a towed, 3-axis receiver called RELEDOP. RELEDOP is a receiving elementary dipole with optional polarization that measures the transmit directivity patterns of over-the-horizon backscatter (OTH-B) radars and shortwave broadcast transmitting arrays. A dielectric tow cable and a fiber-optic link to the towing aircraft permit excellent electromagnetic isolation of the RELEDOP sensor from the aircraft. High accuracy in position location ( plus or minus 15 m in x, y, and z) and fast-receiver sampling permit orthogonal polarization component measurements with accuracies of plus or minus 0. 15 degree in bearing and plus or minus 1 dB in relative amplitude. Calibrated receiving element gains permit measurement of absolute field strength. The field strength data, combined with the position data, permit an assessment of transmitter effective radiated power (ERP); a knowledge of input power permits a computation of absolute gain of the transmitting antenna to plus or minus 3 dB or better. The RELEDOP system is described, along with its subsystems; towed sensor, airborne, positioning, ground station, and communications subsystems. Example patterns and flight path tracks illustrate the output graphics.