40M Reversible Moxon
Build a reversible 40-meter Moxon rectangle with high F/B and directional switching.
Description
A 40-meter reversible Moxon rectangle antenna project details its construction and performance, featuring 51-foot long sides and 7.7-foot turned-in sections. The design incorporates a 16.5-foot boom, with elements spaced 1.1 feet apart, constructed from #14 covered wire. It utilizes two double-pole relays for switching between NE and SW directions, achieving F/B ratios up to 40 dB on CW and 30 dB on SSB, with distinct reflector stub settings for each mode.
This antenna replaced a full-size 2-element Yagi, demonstrating comparable forward gain while offering superior F/B ratios and directional flexibility. EZNEC modeling indicates only 0.2 dB less forward gain than the Yagi. The system uses no baluns, relying on half-wave feedlines and switched stubs for impedance matching. The antenna is tree-supported at 45 feet, with its effective radiation height modeled at 80 feet due to local terrain, enhancing its performance over a nearby lake.