A Cardioid Small Transmitting Loop

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AN-SOF Antenna Simulator Group

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Dec 6, 2022, 8:04:08 AM12/6/22
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Keith Rawlings, G4MIU, drew my attention to the so-called "Loop on Ground (LOG)", which is a small transmitting loop antenna with a cardioid-shaped radiation pattern in the horizontal plane. Keith is the author of the AerialsNow! column in RadioUser Magazine and has already posted about this loop.

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: 2m (average real ground)

This design is not self-resonant, it presents an inductive input impedance that must be matched to the feed line.

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.

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AN-SOF_CardioidLoop.png

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