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 (+or-15 m in x, y, and z) and fast-receiver sampling permit orthogonal polarization component measurements with accuracies of +or-0.15 degrees in bearing and +or-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 +or-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.<
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