Slim Jim / J Pole antenna calculator. Frequency MHz Velocity Factor (see text*) vf Actual wavelength metres Wavelength considering velocity factor metres A. Overall length (λ*0.75)*vf (plus gap for Slim Jim) cm (J Pole) cm (Slim Jim) B. Half wave radiator section (λ/2)*vf cm C. Quarter wave matching section (λ/4)*vf cm D. 50Ω feed point. … Continue reading Slim Jim and J Pole calculator