Resources Contact Us Home
High sensitivity portable radio direction finder

Image Number 3 for United States Patent #4475106.

A simple inexpensive, very effective high to ultra high frequency radio direction finder is disclosed utilizing two parallel antenna units with switching means for alternately connecting the antenna units to a conventional unmodified FM or NBFM receiver at an audio frequency rate. If the centroids of the antenna units are not on a line normal to the path of the monitored input signal, the amplitude of the audible tone output signal resulting from the difference in phase of the alternately received input signals at the time of switching will vary with the angle of deviation of the antennae from this normal position. The slight alternations of phase are demodulated as slight frequency changes and produce a tone in the FM receiver output having the audio frequency of the antenna switching device. When the line between the electrical centroid of the two antennae is rotated to lie normal to the path of the monitored signal as it passes a point midway between the two antennae, the receiver tone output is a null or minimal, whereas it increases in amplitude as the antenna units are rotated further from normal. The apparatus includes automatic circuitry for resolving the ambiguity of the monitored signal source fore or aft of the operator when the output is at null. This is done by providing a positive indication of which way to rotate the antennae to reach the preferred null, and includes both aural and visual output displays.

  Recently Added Patents
Evaluating programmer efficiency in maintaining software systems
Active and progressive targeted advertising
Semiconductor integrated circuit
Fingerprinting apparatus, system, and method
System and method for detecting executable machine instructions in a data stream
Method and device for authenticating transmitted user data
Fibrous laminate interface for security coatings
  Randomly Featured Patents
Hospital bed
Cookware article with internally flush rivets
Method and apparatus for control of content based rich media streaming
Angularly self-aligned optical subassembly
Integrated IR, visible and NIR sensor and methods of fabricating same
Laser link structure capable of preventing an upper crack and broadening an energy window of a laser beam, and fuse box using the same
Solid electrolyte particles comprising MAg4I5
Building panel
Weather tight blind fastener
Automatically inserting relevant hyperlinks into a webpage