VK4FUQ’s optimised sloper antenna for 3.5MHz. Radiator and counterpoise radial are both one-quarter-wave in length (length in metres = 71.37/(frequency in MHz) or in feet 234/MHz). The radial should be at least 5ft (preferably about 8ft) above ground and immediately underneath the radiator. Good quality insulators are need at the top of the preferably non-conductive mast and at the end of the radial.