Radio beacon for a nautical emergency rescue system

Claim 2

In a radio beacon intended for use with a nautical emergency rescue system, the improvement comprising; a waterproof, electrically insulative flotation housing having an upper portion, a lower portion and a central portion, said lower portion being weighted so that when said housing is placed in the water, said lower portion will be submerged, said upper portion will be upright out of the water and said central portion will be at about water surface level, a ground plane mounted within said central portion, an antenna within said housing upper portion including; a conductive rod extending generally perpendicularly upwardly from said ground plane but electrically insulated therefrom, and a conductive cylindrical can extending downwardly, coaxially over said rod, the lower end of said can being open, the upper end of said can being closed and attached at its center to the upper end of said rod, said can being shorter than said rod, and a radio transmitter mounted with said housing and electrically connected to said antenna and to said ground plane.

Claim 3

A radio beacon according to claim 1 further comprising; electrical conduction means extending through said housing for providing electrical connection between said ground plane and said water.

Claim 4

A radio beacon according to claim 1 wherein said radio transmitter is frequency modulated, and including a modulator for alternately shifting the transmitter frequency between two values at a controllable repetition rate.

Claim 5

A radio beacon according to claim 3 wherein said modulator alternately shifts the transmitted frequency at first and second repetition rates, and including modulator control circuitry, cooperating with said modulator, to establish the time duration at which said modulator alternates between said first and second repetition rates.

Claim 6

A radio beacon according to claim 1 together with a direction finding receiver system for receiving the signal transmitted from said transmitter and for finding the direction of said beacon with respect to the receiver system.

Claim 7

A radio beacon according to claim 5 further comprising; duty cycle control circuitry for establishing a duty cycle during which said radio transmitter is on, the off time of said duty cycle being sufficiently long to permit reception and direction finding of the transmitted signals from at least one other like beacon during said off time.

Claim 8

A radio beacon according to claim 1 wherein said radio transmitter is frequency modulated by a modulator to provide a beacon identification code, said receiver system including means for verifying individual beacon identification codes.

Claim 9

A radio beacon according to claim 1 wherein said transmitter is powered by battery, said battery being mounted in said housing lower portion to provide the weight therefor.

Claim 10

A radio beacon according to claim 1 further including insulative material, within said housing upper portion, for maintaining a stable, coaxial relationship between said rod and said can.

Claim 11

A radio beacon according to claim 9 wherein said insulative material is a plastic foam filling the entire area within said housing upper portion.

Claim 12

A radio beacon according to claim 1 wherein said housing upper portion is of inverted truncated conical shape, wherein said central portion is generally disc-shaped with a diameter greater than the maximum diameter of said upper portion, and wherein said lower portion is generally cylindrical.

Claim 13

A radio beacon according to claim 2 wherein said electrical conduction means comprises metal contacts extending through openings in said housing central section and exposed for contact with said water, said openings being sealed to prevent water entry therethrough.

Claim 14

A radio beacon according to claim 2 wherein said ground plane is a planar metal disc having a diameter greater than said housing central portion and extending therethrough, said electrical conduction means comprising the annular peripheral section of said disc that extends beyond said housing.

Claim 15

A radio beacon according to claim 2 further comprising a channel region within said housing central portion in fluid communication with said water, a portion of said ground plane extending into said channel region to establish electrical contact between said ground plane and said water when said beacon is in use.

Claim 16

A radio beacon according to claim 1 together with a modulator for providing a coded modulation of the transmitted beacon signal, and switch means connected to said modulator for selecting different modulation codes.

Claim 17

A radio beacon according to claim 1 together with; a magnetic switch mounted within said waterproof housing and connected to turn on power to said transmitter, and moveable means, including a magnet, mounted on the outside of said housing opposite said switch and including a magnet to actuate said switch when said means is moved.

Claim 18

A nautical emergency rescue system comprising; a plurality of beacons each having an antenna, a ground plane, a transmitter connected to said antenna and ground plane, and a modulator for said transmitter all contained in a flotation case, said modulator providing frequency modulation of said transmitter with a repetitive, selectable pattern including a component at audio frequency, the pattern of each beacon being uniquely different from the pattern of the other beacons, a duty cycle control circuit for said beacon, contained within said case, for alternately turning on said transmitter for a time duration sufficient to permit detection and direction finding of said beacon and for turning off said transmitter for a time duration sufficient to permit detection and direction find of other like beacons operating on the same frequency, and a direction-finding receiver system for detecting and finding the direction of plural such beacons, the unique modulation pattern facilitating identification of each detected beacon.

Claim 19

A nautical emergency rescue system comprising; a plurality of beacons each having an antenna, a ground plane, a transmitter connected to said antenna and ground plane, and a modulator for said transmitter all contained in a flotation case, said modulator providing frequency modulation of said transmitter with a repetitive, selectable pattern including a component at audio frequency, the pattern of each beacon being uniquely different from the pattern of the other beacons, a duty cycle control circuit for said beacon, contained within said case, for alternately turning on said transmitter for a time duration sufficient to permit detection and direction finding of said beacon and for turning off said transmitter for a time duration sufficient to permit detection and direction find of other like beacons operating on the same frequency, and a direction-finding receiver system for detecting and finding the direction of plural such beacons, the unique modulation pattern facilitating identification of each detected beacon.

Claim 20

A system according to claim 17 wherein said flotation case includes an upper section containing said antenna, a central section containing said ground plane, and a lower section containing batteries to power said transmitter, said batteries weighting said lower section so that when placed in a body of water said lower section will be submerged and said upper, antenna-containing section will be above the water surface, and wherein each beacon further includes an emergency indicating code selector switch and associated circuitry for modifying the modulation pattern so as to provide both identification of said beacon and a code indicating the nature of the emergency causing use of the beacon.

Claim 21

A system according to claim 18 wherein said beacon also includes means for providing electrical conduction between said ground plane and said water, and wherein the duty cycle includes an on-time on the order of about 15 seconds followed by an off-time on the order of about 60 seconds.

Claim 22

A nautical emergency rescue system comprising: a beacon having an antenna, a ground plane, a transmitter connected to said antenna and ground plane, and a modulator for said transmitter all contained in a flotation case, said modulator providing frequency modulation of said transmitter with a repetitive, selectable pattern including a component at audio frequency, a duty cycle control circuit for said beacon, contained within said case, for alternately turning on said transmitter for a time duration sufficient to permit detection and direction finding of said beacon and for turning off said transmitter for a time duration sufficient to permit detection and direction find of other like beacons operating on the same frequency, a direction-finding receiver system for detecting and finding the direction of plural such beacons, and wherein said ground plane is a metal disc, and said antenna includes a rod extending perpendicularly to said ground plane and an inverted can having one open end mounted coaxially with said rod, said rod being attached to the center of the can closed end, said can being shorter than said rod, and insulative means for maintaining said can concentric with said rod and in spaced relationship above said ground plane.

Claim 23

A nautical emergency rescue system comprising: a beacon having an antenna, a ground plane, a transmitter connected to said antenna and ground plane, and a modulator for said transmitter all contained in a flotation case, said modulator providing frequency modulation of said transmitter with a repetitive, selectable pattern including a component at audio frequency, a duty cycle control circuit for said beacon, contained within said case, for alternately turning on said transmitter for a time duration sufficient to permit detection and direction finding of said beacon and for turning off said transmitter for a time duration sufficient to permit detection and direction find of other like beacons operating on the same frequency, a direction-finding receiver system for detecting and finding the direction of plural such beacons, and wherein said ground plane is a metal disc, and said antenna includes a rod extending perpendicularly to said ground plane and an inverted can having one open end mounted coaxially with said rod, said rod being attached to the center of the can closed end, said can being shorter than said rod, and insulative means for maintaining said can concentric with said rod and in spaced relationship above said ground plane.