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The W8JK is a famous and effective DX antenna, first built by John Kraus, W8JK, in 1937. A Beam antenna with two parallel dipoles driven with opposite phase, with a close spacing of an eighth of a wavelength.

F6DED page of a 2 element beam W8LK antenna with pictures and dimensions, in french

A compact 2 element W8JK beam antenna for 20M to 10M bands by AF6SA

Examines the design and performance of a compact, efficient multiband beam antenna, based on a modified **W8JK array** by K5LJ. The author recounts his quest for a simple, compact, and reasonably efficient beam, initially using a single delta loop for 40 meters. He then details his modeling efforts with EZNEC, focusing on a W8JK array using 20-meter dipoles, noting its venerable design history in various Antenna Handbooks and QST. The resource explains how the classic W8JK array, composed of 0.5-lambda elements at the lowest operating frequency, uses a closely spaced phasing line to connect feedpoints, often 450-ohm ladder line. K5LJ's modifications, including offsetting the feedpoint on the phasing line, resulted in surprising gain and a somewhat unidirectional pattern on 20 meters, rivaling a full-sized Yagi. The article also delves into mechanical construction details, using nested tubing and PVC pipe for element isolation, and discusses the feedpoint impedance characteristics across multiple HF bands.

A W8JK/Moxon antenna variant with 400cm long monopoles is detailed, demonstrating a **1dbd** gain improvement over the traditional Open-Folded W8JK. This design, relying on the _Moxon principle_, achieves higher radiation impedance, leading to increased antenna efficiency and reduced losses. The article includes VNA output data for various HF bands, showing impedance characteristics from 10.1 MHz to 50.1 MHz, and provides NEC model wire definitions for the antenna structure. Field tests performed by F6IIV, Marc, compared his W8JK Moxon style antenna against a Cobweb antenna at the same height. Results indicated the W8JK Moxon variant provided a **6dB** (1 S-meter point) advantage on most bands from 20m to 10m, and a significant 10dB (1.5 S-meter points) advantage on 15m. The antenna features a 2.70m boom and a turning radius of less than 3 meters, making it suitable for limited space installations while maintaining bi-directional performance on most bands.

Originally designed by John Kraus, W8JK in about 1940, this antenna has some interesting properties. The W8JK antenna is 2 (Two) centre-fed double-dipole fed by a pair of anti-phase signals. Small size, simple antenna, offer nice performance but need a tuner. Tested in this project from 30m to 6m bands

The PA0FRI Unbalanced/Balanced ATU is a home-built antenna tuner designed to efficiently match a W8JK 2-element beam antenna fed with a 450-ohm twin lead. Based on PA0FRI’s S-Match design, it optimizes energy transfer while maintaining balance, reducing losses, and ensuring proper radiation. The tuner uses a roller inductor, air variable capacitors, and a T200 iron powder coil, allowing fine-tuning across 14-50 MHz. Extensive lab tests confirm minimal attenuation and precise impedance matching, making it a reliable and efficient ATU for balanced antennas.