ETS-Lindgren's Model 3151 Log-Periodic Dipole Array (LPDA) Antenna features a convenient space saving design with the use of top hat-loaded, low-frequency elements. The reduced-sized design of this log antenna has optimized impedance loading to simulate the moderate gain of a full-size LPDA. Without size reduction, the longest dipole element length would be approximately 7.5 m (24.6 ft). Instead, this antennas entire width is only 3.5 m (11.5 ft).
To enhance measurement repeatability, the model 3151s longest elements are supported with nylon straps to ensure consistent element positioning. The 3151 antenna features a specially-designed feed to handle high power requirements of up to 5 kW for generating high electric field strength. A hairpin matching stub is used to improve the low-frequency VSWR, which minimizes mismatch loss between the amplifier and antenna.
The antenna is constructed of lightweight, corrosion-resistant aluminum, providing years of trouble-free service. All elements are attached with knurled knobs for easy assembly. The included wheeled pedestal permits horizontal and vertical antenna polarization, and tilt-angle adjustments. A pneumatic cylinder is used to change polarization, and can be remotely controlled using an optional ETS-Lindgren controller.