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:
“Your Englishman, confronted by something abnormal will always pretend that it isn’t there. If he can’t pretend that, he will look through the object, or round it, or above it or below it, or in any direction except into it. If, however, you force him to look into it, he will at once pretend that he sees the object not for what it is but for something that he would like it to be.”
—James Agate (1877–1947)
“There comes a point in many people’s lives when they can no longer play the role they have chosen for themselves. When that happens, we are like actors finding that someone has changed the play.”
—Brian Moore (b. 1921)
“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)