Compact Open Sleeve Dipole Antenna for 40 and 20 Meters

This resource details the construction of a compact dual-band open sleeve dipole antenna designed for 40 and 20 meters. The antenna utilizes 450-ohm ladder line, achieving a total length of approximately 17.17 meters, which is shorter than a conventional half-wave dipole for 40 meters. Length reduction is accomplished by folding back the outer sections of the dipole elements. The design employs electromagnetic coupling, where a primary radiator handles the 40-meter band, and a second conductor resonates on 20 meters without a direct electrical connection. This configuration eliminates the need for traps, loading coils, or switching components. The antenna is fed with RG-58C/U coaxial cable, and a common-mode choke is recommended at the feed point to suppress sheath currents. This design is suitable for portable stations, field operation, temporary installations, and restricted urban environments.