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:
“That reality is ‘independent’ means that there is something in every experience that escapes our arbitrary control. If it be a sensible experience it coerces our attention; if a sequence, we cannot invert it; if we compare two terms we can come to only one result. There is a push, an urgency, within our very experience, against which we are on the whole powerless, and which drives us in a direction that is the destiny of our belief.”
—William James (1842–1910)
“One of the many reasons for the bewildering and tragic character of human existence is the fact that social organization is at once necessary and fatal. Men are forever creating such organizations for their own convenience and forever finding themselves the victims of their home-made monsters.”
—Aldous Huxley (1894–1963)
“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)