W8JK Bi-directional Antenna
The W8JK is a famous and effective DX antenna first built by John Kraus, W8JK, in 1937.
Kraus built the first W8JK beam antenna with two parallel dipoles driven with opposite phase, with the unprecedented close spacing of an eighth of a wavelength.
The W8JK antenna is a classical antenna in our series of HS4 Legendary Multiband Wire Antennas. It covers 5 bands, 10-12-15-17-20m. Unlike typical antennas, this is a non-resonant, center-fed antenna. The performance characteristics are absolutely outstanding. The antenna consists of two symmetrical length horizontal radiating elements being driven at 180 degrees out of phase at a common feedpoint through a 450 Ohm slotted ladder transmission line (TL). The principle of a W8JK utilizes the radiating elements and the ladder line section of pre-defined length for taming the SWR to workable limits.
This antenna needs an antenna tuner for proper operation. The overall gain on all bands is very good with adequate low angle radiation for great DX. This antenna is deployed at a height of 12m (40 ft.) above average quality ground and the design accounts for ground absorption losses, antenna wire insulation dielectric losses, other structural losses, etc.
The most important feature of this antenna is that it produces very well defined bidirectional and broad width azimuth pattern with good gain on all bands. The original W8JK was only meant for regular HF amateur radio bands and did not cover the WARC bands of 17m and 12m. The modified W8JK presented here includes the intermediate WARC bands too... Happy DXing!