SOTA 3-Band Vertical Antenne with Loading Coil

thingiverse

This is a three-band base-loaded ham radio antenna designed for use on 40, 30, and 20m frequencies. It can be used with a 6m fiberglass mast from lambdahalbe.de; it may also fit other similar masts. You will need two 2mm gold-plated plugs, which are typically used in RC car batteries, as well as 0.6-0.7mm enamel wire for the loading coil. The radiator should be approximately 5m long so that the coil sits about 1m above ground. To achieve resonance, the coil should have between one and two turns for 20m, six to seven more turns for 30m, and eight additional turns for 40m. However, you will need to fine-tune this setup based on your specific needs. You can use the 2mm plugs to shorten the parts of the coil not required for the band in use. Additional details are available at http://reflector.sota.org.uk/t/sota-vertical-antenna-for-40-30-20m/15673. It is also possible to add a small balun behind the BNC plug, using 11 turns of twisted enamel wire on an FT50-43 toroid.