Sky loop antenna
From HF Underground
A loop antenna in the horizontal plane. Typically at least 1 wavelength in circumference, for receiving purposes any size will work, the larger the better. Due to the high impedances involved, the antenna is often fed with a balun, such as 9:1, 12:1 or even 16:1. It could also be fed with balanced line, such as twin lead.
Being a loop antenna, the noise pickup is generally much lower than other antennas such as the dipole.