Model 503

The 503 provides directional coverage over a 120° azimuthal sector. At the higher frequencies, most frequently used on long paths, the phase center of the structure is elevated, giving increased gain and lower take-off angles. This results in increased signal strength on long paths.

Front-to-back ratio of the 503 is especially good (14 dB at 2.5 MHz, 19 dB above 4 MHz on 503-1), reducing the susceptibility of the communications system to interference. VSWR is under 2.0:1.

The 503’s novel structural design results in the smallest and shortest dipole log periodic for a given bandwidth. The feedline is used as a catenary element, greatly reducing the loads transferred by the radiators in severe environments. This permits the use of a flatter top catenary, elimination of “drop rod” material, and a shorter tower. The result is a much more compact, economical structure. As in other 500 series antennas, no fiberglass is used in the catenary and support structures. A precisely manufactured, electrically transparent Alumoweld structure is used instead.