Ground plane questions

[david.baker]

I found one of the discussion about angle of the legs and impedance. There are probably more if you want to look.

Tweaking of Groundplane (Spider) Antenna

It is well known that in a Groundplane antenna, the slope of radials affects its impedance, and hence affects SWR. If slope = 0 degrees (i.e. radials are horizontal), Antenna Impedance is around 30 ohms If slope = 45 degrees down (i.e. radials are slanting), Antenna Impedance is around 50 ohms If slope = 90 degrees down (i.e. radials are vertical), Antenna Impedance is around 75 ohms Before the advent of ADS-B, the Groundplane/Spider was mainly used by Hams. Since the defacto standard of ham …