Compact Open Sleeve Dipole Antenna for 40 and 20 Meters

Constructing a dual-band antenna for 40 and 20 meters often involves compromises in size or complexity. This resource presents a compact open sleeve dipole design that addresses these challenges by using 450-ohm ladder line and folded elements to achieve a total length of approximately 17.17 meters, significantly shorter than a full-size 40-meter dipole. The design leverages electromagnetic coupling, where a primary radiator handles the 40-meter band, and a second conductor resonates on 20 meters without direct electrical connection.

This configuration eliminates the need for traditional traps, loading coils, or switching components, simplifying construction and reducing potential loss points. 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, ensuring a cleaner radiation pattern and minimizing RF in the shack. The design is well-suited for portable operations, field deployments, temporary installations, and restricted urban environments where space is a premium, offering solid performance on both HF bands.