A Cardioid Small Loop
The so-called “Loop on Ground (LoG)” is a small loop antenna with a cardioid-shaped radiation pattern in the horizontal plane, used for reception.
The loop has a 110 Ohm resistor connected to its top, while the antenna terminals are located at the bottom. One of the terminals is connected to ground by a vertical wire, forming a monopole. This is the secret to getting this antenna, despite being small, to be directional.
The image below shows the radiation patterns obtained with and without grounding.
Frequency: 4.5 MHz
Loop diameter: 1 m
Height above ground: 2 m (average real ground)
The segmentation used in the Conformal Method of Moments is observed over the antenna. Very few segments are needed because it is a small antenna in terms of the wavelength.