Which of the following is a common way to adjust the feed point impedance of an elevated quarter-wave ground-plane vertical antenna to be approximately 50 ohms?
Why A quarter-wave vertical over perfectly horizontal radials shows a feed point impedance near 36 ohms, which is a poor match for 50-ohm coax. Drooping the radials downward, typically around 45 degrees, raises the feed point impedance to roughly 50 ohms and gives a good match. The sloped radials also make the radiation pattern a bit more like a half-wave dipole fed at the center.
Watch out Sloping the radials upward moves the impedance the wrong way, lowering it further below 36 ohms; radial length and coiling are used for tuning resonance or for trap/loading tricks, not for setting the 50-ohm match this way.
Radials droop down to bring 36 ohms up to 50. Down for up.