17 Meter Coaxial Moxon Antenna
Build a compact 17-meter coaxial Moxon rectangle with an MFJ-259B.
Description
Constructing a reduced-size coaxial Moxon rectangle antenna for the 17-meter band is detailed, presenting a method to achieve a compact directional antenna. The resource outlines the use of RG-58/U coaxial cable for elements, enabling a substantial reduction in physical dimensions compared to traditional wire or tubing Moxon designs. It provides specific instructions for tuning coaxial elements using an MFJ-259B antenna analyzer, including a formula to calculate trimming lengths based on measured resonance and desired frequency. The article explains how to prepare the coaxial cable for both driven and reflector elements, specifying connections for testing and final assembly.
Performance data from an MFJ-259B shows SWR readings between 1.0 and 1.2 across 18.068 MHz to 18.168 MHz, with R values from 51 to 59 ohms and X values of 0 or 6 ohms. The antenna's power handling is approximately 500 watts continuous, limited by the RG-58/U coax. Comparative receive testing against an All-Band Sterba Curtain at 50 feet indicated a 2 S-unit reduction for the coaxial Moxon at 9 feet, suggesting optimal performance at a height of 34-40 feet for a 15-18 degree take-off angle. The design achieves an electrical quarter wavelength with over 30 percent size reduction.