This led to the 1919 introduction of the Adcock antenna ( UK Patent 130, 490 ), which consisted of four separate monopole antennas instead of two loops, eliminating the horizontal components and thus filtering out the sky waves being reflected down from the ionosphere.
12.
The Adcock antenna array has been widely used commercially, and implemented in vertical antenna heights ranging from over 130 feet ( 40 meters ) in the LFR network, to as small as 5 inches ( 13 cm ) in tactical direction finding applications ( receiving in the UHF band ).
