The OB2-40 is a particularly compact but powerful monoband Yagi antenna for the 40 m amateur radio band. It was developed using computer-aided design, optimised through extensive practical testing, and offers exceptional performance in a limited space. With a gain of 3.6 dBd (10.8 dBi) and a front-to-back ratio of 15 dB, it almost matches the performance of much larger full-size Yagis.

To reduce the typically long elements in the 40 m band, specially developed high-Q coils (no traps) from OptiBeam are used, which enable low-loss shortening. The resulting impedance of approx. 30 ohms is adjusted back to 50 ohms via a pre-mounted hairpin match. A high-quality 1:1 balun with a power handling capacity of up to 5 kW is included in the scope of delivery.

The antenna is based on a stable 80 × 80 mm aluminium boom. It has two guyed elements with a maximum element length of 15 m, a boom length of 5.6 m, and a turning radius of 7.96 m. The total weight is 35 kg. The wind load at 130 km/h is 500 N (equivalent to 0.62 m²).

The element design allows two selectable assembly variants for frequency-specific optimisation in accordance with different international band segments:

• If a special element section marked “CW / Europe” is installed, the optimum operating range is between 7,000 and 7,200 kHz – ideal for the European band plan and CW operation. The 7,200–7,300 kHz range remains limited, sometimes with the aid of a tuner.
• If, on the other hand, the section marked “USA phone” is selected, the antenna is tuned to the upper band range between 7,150 and 7,300 kHz, which corresponds in particular to North American SSB operation. In the lower band range, the SWR is then significantly less favourable and not suitable for transmission operation.

Depending on the setting, the measured SWR values are typically between 1.1 and 1.6, with a maximum of 1.9 at the edge of the band.

Specially developed decoupling stubs are used to reduce unwanted coupling effects with neighbouring antennas in the 10–20 m range. These consist of 2 mm thick V2A wire, run below the outer element halves, and are tensioned and stabilised via plastic insulators.

The OB2-40 is the ideal choice for demanding radio amateurs who want to operate a powerful directional antenna for the 40 m band despite limited space – with a well thought-out design, robust mechanics, and practical frequency adjustment.