US PATENT SUBCLASS 342 / 389-- .~.~.~.~.~ Loran-C

US PATENT SUBCLASS 342 / 389
.~.~.~.~.~ Loran-C

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}
389		.~.~.~.~.~ Loran-C {1}
390	DF	.~.~.~.~.~.~> With cycle selection

DEFINITION

Classification: 342/389

Loran-C:

(under subclass 388) Subject matter wherein the loran system provides a coarse measurement of time-difference through the matching of pulse envelopes, and a fine measurement by the comparing of phase between the carrier wave.

(1) Note. Loran-C is generally useful to distance of 1,000 to 1,500 nautical miles (1,850 to 2,800 kilometers) over water; it uses a baseline of about 500 nautical miles and operates at approximately 100 kilohertz.

(2) Note. A typical example of Loran-C system would include a master station nine at a repetition rate of 10 to 25 groups per second with a spacing of 1,000 micro sec between the pulses of a group; a slave station which after a delay of at least the one-way time from master to slave, plus and additional 2,000 micro sec transmits an eight pulse group, also spaced 1,000 micro sec and later still another slave station which transmits a similar group, and wherein the apparatus receiving these pulses conducts the following operations. (1) Searching for the master signal; (2) Identifying it by repetition rate and phase code; (3) Locking a local reference oscillator onto the master signals; (4) Locking onto the two or more slave signals; and (5) Determining their time difference from the master (commonly these differences are manually translated to hyperbolic lines on a chart).