A recent online discussion contained an analysis of the radiation efficiency of a vertical monopole over real ground.
The poster dismissed the values calculated by 4NEC2 and proposed his own formula \(RadiationEfficiency=\frac{35.6}{\mathbb{R}Z_f}\) where 35.6 is the radiation resistance Rr of a quarter wave monopole over a perfectly conducting earth (PCE).
The reasoning seems to depend on Rr being independent of the ground type, but that is quite flawed.
NEC insight
Let us look at an example of a quarter wave monopole with 120 shallow buried radials, average ground, at 3.8MHz.
Above is the model geometry. Continue reading NEC – vertical monopole radiation resistance study