Direction Finding With Loops
Since the directional response of small loop antennas includes a sharp null in the direction normal to the plane of the loop, they are used in radio direction finding at longer wavelengths. The loop is thus rotated to find the direction of the null. Since the null occurs at two opposite directions, other means must be employed to determine which side of the null the transmitter is on. One method is to rely on a second loop antenna located at a second location, or to move the receiver to that other location, thus relying on triangulation.
A second dipole or vertical antenna known as a sense antenna can be electrically combined with a loop or a loopstick antenna. Switching the second antenna in obtains a net cardioid radiation pattern from which the general direction of the transmitter can be determined. Then switching the sense antenna out returns the sharp nulls in the loop antenna pattern, allowing a precise bearing to be determined.
Read more about this topic: Loop Antenna
Famous quotes containing the words direction, finding and/or loops:
“Exaggeration is in the course of things. Nature sends no creature, no man into the world, without adding a small excess of his proper quality. Given the planet, it is still necessary to add the impulse; so, to every creature nature added a little violence of direction in its proper path, a shove to put it on its way; in every instance, a slight generosity, a drop too much.”
—Ralph Waldo Emerson (1803–1882)
“The great problem of American life [is] the riddle of authority: the difficulty of finding a way, within a liberal and individualistic social order, of living in harmonious and consecrated submission to something larger than oneself.... A yearning for self-transcendence and submission to authority [is] as deeply rooted as the lure of individual liberation.”
—Wilfred M. McClay, educator, author. The Masterless: Self and Society in Modern America, p. 4, University of North Carolina Press (1994)
“In the labyrinth of a difficult text, we find unmarked forks in the path, detours, blind alleys, loops that deliver us back to our point of entry, and finally the monster who whispers an unintelligible truth in our ears.”
—Mason Cooley (b. 1927)