EFHW Compensation Coil

When tuning an EFHW antenna, when you get the antenna tuned on 40m, the higher bands will be out of tune as the tune for the antenna creeps lower into the band. This coil will help shorten the antenna on the higher bands without affecting the lower ones too much. This form is designed for 3mm diameter antenna wire, but smaller diameters will also work just fine. When calculating the inductance of the coil, it is right around 1.5 microhenries. The coil should be placed 78 inches from the feed point. Coil 9 turns of your antenna wire tightly onto the form and use zip ties to secure it. You can use electrical tape or heat shrink to further keep it in place. If you are permanently mounting this antenna, use ASA for its UV and heat resistance (I used ASA-CF). If making this for a portable antenna, you may get away with using PETG, but I do not recommend it. Boost MeIf you like my models, please give it a boost, it greatly helps me out!