US PATENT SUBCLASS 342 / 391
.~.~.~.~.~ Loran-A

Current as of: June, 1999
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342 /   HD   COMMUNICATIONS: DIRECTIVE RADIO WAVE SYSTEMS AND DEVICES (E.G., RADAR, RADIO NAVIGATION)

350  DF  DIRECTIVE {10}
385  DF  .~ Beacon or receiver {2}
386  DF  .~.~ With transmisson of bearing or position determinative signals {6}
387  DF  .~.~.~ Iso-chronic type {2}
388  DF  .~.~.~.~ Loran {2}
391.~.~.~.~.~ Loran-A

DEFINITION

Classification: 342/391

Loran-A:

(under subclass 389) Subject matter wherein the Loran system provides time-difference measurement by matching the leading edges of the pulses (usually with an oscilloscope).

(1) Note. Loran-A is generally useful to distances of 500 to 1,500 nautical miles (900 to 2,800 kilometers) over water and it uses a baseline of about 300 nautical miles 550 kilometers) while operating at approximately 2 megahertz.

(2) Note. A typical example of a Loran-A system would include a master station transmission of pulses which are received and rebroadcast by the slave stations to be ultimately received by the vehicular receiver which measures the differential delay between reception of the master pulses and slave pulse (usually by oscilloscope observation of the time difference), and for each such differential time, there is a hyperbolic line of position with master and slave as foci, wherein the intersection of two such lines, one from each slave, provides a fix (commonly the oscilloscope readout is manually translated to a chart on which the hyperbolic lines are already printed).

(3) Note. Various chains or Loran-A systems are distinguished from each other by using three carrier frequencies and twenty four sets of pulse repetition rates.