Abstract: The present invention provides an underwater wireless communications hotspot comprising an active zone which is circumscribed by a large closed loop antenna and within which wireless communication by means of electromagnetic signals can take place. The wireless communications hotspot of the present invention is suitable for data transfer between a communications node of the wireless hotspot and a receiver mounted on a mobile unit which is located inside the active zone of the hotspot. The wireless hotspot of the present invention provides a means for high bit rate data transfer from the communications node and the mobile unit, due to improved uniformity of coverage within the active zone of the hotspot and due to a reduction in the attenuation with distance compared to communications at positions outside the perimeter of a loop antenna.

Abstract: Methods and apparatus for marine deployment according to various aspects of the present invention may operate in conjunction with a floatable housing adapted to be deployed by a marine vehicle. The floatable housing may be adapted to be launched from a marine vehicle and rise to the surface. Assets, such as an unmanned aerial vehicle, may be deployed from the surfaced floatable housing.

Abstract: The invention as disclosed is of a buoyant cable antenna for use with underwater vehicles having improved bandwidth through the use of discrete distributed loading along the antenna. The buoyant cable antenna is designed with an antenna wire that is divided into N equal length segments of length d/2. A capacitor is coupled between every other segment such that capacitors are separated by a distance d. A shunt inductor is coupled to the antenna wire between the adjoining segments not separated by a capacitor such that the shunt inductors are separated by a distance d. This antenna design provides a substantially improved impedance bandwidth over existing prior art antennas at high frequency without increasing the physical profile of the antenna and without the use of active circuit elements.

Abstract: A linear antenna for operation in the HF frequency range, particularly for naval communications is disclosed, comprising a radiating arrangement (H1, H2, H3, W1, W2), adapted to be operatively associated with a ground conductor (20) and at least one electrical impedance device (Z1-Z4), characterized in that it includes: a plurality of wire radiating elements with a predominantly vertical extension, forming a first and a second conducting branch (H1, H2) adapted to be operatively coupled to a feed circuit, and a return conducting branch (H3) adapted to be operatively coupled to a ground conductor (20); and a plurality of wire radiating elements with a predominantly transverse extension, forming connecting conducting branches (W1, W2) for connecting the conducting branches (H1, H2) adapted to be coupled to the feed circuit (12), to the conducting branch (H3) adapted to be coupled to the ground conductor (20), the radiating elements being positioned in such a way as to form, in a plane in which the antenna lies,

Abstract: An antenna system, with a loop antenna and a loop current, is provided for transmitting an electromagnetic signal through a medium. The loop antenna has an E field transducer that generates an E field, and an H field transducer that generates an H field. The E and H fields are orthogonal in space and have at least one of a magnitude and phase relationship that is matched to an intrinsic impedance of a medium to generate a propagating wave. In an insulating medium the loop current lags an E field plate voltage by 90° to produce in phase E and H fields. In a conductive medium current is applied to the loop with a 135° phase lag with respect to a voltage across the E field plates. The H field is generated by the current component and leads current by 90°.

Abstract: An underwater communication method is provided. EM signals are transmitted via a seabed using an underwater electrically insulated magnetically coupled antenna. By making use of the low loss properties of the seabed, EM signal attenuation can be reduced and consequently the transmission range can be increased. The underwater electrically insulated magnetically coupled antenna may be located within a body of water or may be buried in the seabed.

Abstract: The present invention provides an antenna for underwater radio communications. The antenna of the present invention comprises an elongate section submerged in water and a feed point for feeding electrical signals to the antenna located on the elongate section, the elongate section is attached to an underwater object at a first end thereof, and during deployment hangs downwards there from so that said elongate section is substantially vertical in orientation. A first portion of the elongate section comprises a flexible wire having an electrically conductive core, which is electrically insulated on an outer surface thereof. During operation the flexible wire radiates electromagnetic signals through the water.

Abstract: The present invention provides a buoy supported antenna for underwater radio communications. The antenna of the present invention comprises an elongate section submerged in water and a feed point for feeding electrical signals to the antenna located on the elongate section, the elongate section is attached to an underwater object at a first end thereof, and during deployment is suspended by a buoy at a second end thereof so that the elongate section is substantially self supporting and vertical in orientation. At least a first portion of the elongate section comprises a flexible wire having an electrically conductive core, which is electrically insulated on an outer surface thereof. During operation the flexible wire radiates electromagnetic signals through the water.

Abstract: A system for mounting a wireless antenna and equipment to a stealth communication tower in coastal areas and inland waterways, camouflaged as a sailboat. The Cellboat is retrofitted to securely and discreetly store wireless transceiver equipment, and an antenna is attached at the top of the mast. Access doors are disposed in the side of the Cellboat to provide access to the equipment for maintenance purposes. The Cellboat is stored at drydock, allowing for access and protection from flooding of the equipment. Alternatively, when the Cellboat is deployed in the water, the access doors will be located on the top deck of the Cellboat.

Abstract: An underwater communication method is provided. EM signals are transmitted via a seabed using an underwater electrically insulated magnetically coupled antenna. By making use of the low loss properties of the seabed, EM signal attenuation can be reduced and consequently the transmission range can be increased. The underwater electrically insulated magnetically coupled antenna may be located within a body of water or may be buried in the seabed.

Abstract: The invention as disclosed is of a buoyant cable antenna for use with underwater vehicles having improved bandwidth through the use of discrete distributed loading along the antenna. The buoyant cable antenna is designed with an antenna wire that is divided into N equal length segments of length d/2. A capacitor is coupled between every other segment such that capacitors are separated by a distance d. A shunt inductor is coupled to the antenna wire between the adjoining segments not separated by a capacitor such that the shunt inductors are separated by a distance d. This antenna design provides a substantially improved impedance bandwidth over existing prior art antennas at high frequency without increasing the physical profile of the antenna and without the use of active circuit elements.

Abstract: A marine multiband antenna array includes a nearly virtual bowtie UHF antenna and a connected VHF/FM antenna that together function as an AM antenna. A diplexer separates the AM/FM radio signals from the UHF/VHF television signals.

Abstract: Apparatus includes a buoyant structure having a central vertical axis when floating in water and having at least one feature to reduce a rotation of the buoyant structure about the central vertical axis when floating in the water. The apparatus further includes an electronic camera assembly coupled to the buoyant structure. The electronic camera assembly is configured to generate an electronic image signal. The apparatus further includes a tubular structure coupled to the buoyant structure and configured to remain under the surface of the water. The tubular structure includes a watertight compartment and an electronic circuit assembly disposed within the watertight compartment. The electronic circuit assembly is coupled to receive the electronic image signal and is configured to generate an optical image signal representative of the electronic image signal. The apparatus further includes a fiber optic cable configured to carry the optical image signal.

Abstract: An antenna stabilizing apparatus for use on a marine vessel comprises a base body, a housing, a carrier, and a limiting member. The housing is mounted on a top of the base body and internally defines a receiving space. The carrier has at least one antenna carried thereon, and is connected to the house via a hanging member to suspend in the receiving space. The limiting member interconnects the carrier and a bottom of the housing to each other and limits a displacement range allowable for the carrier. With these arrangements, the antenna stabilizing apparatus is able to minimize the adverse influence of the rolling and pitching marine vessel on the signal receiving and transmitting via the antenna mounted on the marine vessel. Therefore, the marine vessel can navigate the sea more safely and stable wireless signal transmission via the antenna mounted on the marine vessel can be ensured.

Abstract: A frequency selective surface-based (FSS-based) device (200) for processing electromagnetic waves providing at least a third-order response. The FSS-based device includes a first FSS (202), a second FSS (210), and a high quality factor (Q) FSS (206) interposed between the first and second FSSs. A first dielectric layer (204) and a second dielectric layer (208) separate the respective FSS layers. The first and second FSSs have first and second primary resonant frequencies, respectively. The high Q FSS has a lower primary resonant frequency relative to the first and second primary resonant frequencies. The overall electrical thickness of the PSS device can be <?/10. The high Q FSS has a loaded quality factor of at least thirty at the lower primary resonant frequency.

Abstract: A multi-function, field-deployable resource harnessing apparatus having, in its embodiments, an inflatable reflector apparatus comprising at least one manufactured parabolic mirror made from a pressure-deformable reflective covering of an inflatable ring for focusing electromagnetic energy from radio frequency radiation (RF) through the ultraviolet (UV) radiation including solar energy. A first main embodiment of the inflatable reflector apparatus generally utilizes two pressure-deformable membranes, at least one of which is reflective. A second main embodiment utilizes a reflective membrane and a transparent membrane. In addition to the reflector apparatus, the modular apparatus typically further includes modular assemblies to increase versatility facilitate use, and/or enhance safety such as, for example, a modular support and orienting assembly, a separate support ring, a safety shield or cage, a focal point support assembly, a safety cover, a safety net or mesh, and a stabilizing assembly.

Abstract: The generator device is proposed for seabed survey, comprising a generator line, including electrodes, a hoist, hydraulic pump, air compressor, and at least one hose joined to the generator line, situated optionally inside or outside the line. The hose includes a through hydro-channel therein, a stationary end connected to the pump or alternatively to the compressor, and a running end furnished with a discharge valve. Connecting to the compressor ensures positive floatation of the generator line, whereas connecting to the pump ensures negative floatation thereof. In preferred embodiments, the device comprises a hydraulic clutch and a faucet. The hose communicates with the pump and compressor through the clutch and faucet, ensuring alternative communication of the hose's hydro-channel with water or air for filling thereof. The generator line comprises a dipole including one power braiding, and an initial part including two power braidings, the braidings are connected to the electrodes.

Abstract: An open-ocean fish-growing platform has a submersible cage structure for growing fish, an antenna for receiving positioning signals transmitted from an external source, a position-correction apparatus for calculating a position error signal from a target geostatic position, and an ocean thermal energy conversion (OTEC) system for generating electric power for thruster units to maintain the cage structure in the target geostatic position. The OTEC system inducts colder ocean water from a deeper ocean depth for driving its heat exchange cycle, and is also of hybrid type using a fuel-fired unit as a heat source. The cold water effluent from the OTEC system is directed into the cage for flushing wastes generated by the growing fish. The self-positioning, self-powered open-ocean platform enables unmanned, extended marine deployment in deeper ocean waters without the need for tethering or anchoring to the ocean floor.

Abstract: The invention as disclosed is a recoverable tethered optical fiber buoy and winch assembly that is mounted to the back of the sail or the back of an aft non-moving surface of an underwater vehicle and housed in a configuration to provide very little additional drag to the underwater vehicle when the assembly is not deployed. The invention provides a capability to connect ocean surface visual or radio frequency sensors to an underwater mobile platform with a very high data rate link that is retrievable.

Abstract: A magnetic and/or magneto-electric antenna that has a plurality of conducting loops that each can be resonated at a frequency that is offset from the other loops to provide a composite band-pass response that is broader than that of the individual loops.

Abstract: Methods and apparatus for marine deployment according to various aspects of the present invention may operate in conjunction with a floatable housing adapted to be deployed by a marine vehicle. The floatable housing may be adapted to be launched from a marine vehicle and rise to the surface. Assets, such as an unmanned aerial vehicle, may be deployed from the surfaced floatable housing.

Abstract: A structural antenna system for operation in the HF frequency range, particularly for naval communications, is described, comprising at least one linear radiating arrangement (14) adapted to be operatively associated with a ground conductor (GND) and at least one electrical impedance device (Z1-Z4), in which the aforesaid linear radiating arrangement (14) is coupled to a pre-existing naval structure which has a predominantly vertical extension and is electrically conducting, such as a funnel (F). A structural antenna system with multiple feed comprises a plurality of linear radiating arrangements (114) positioned in meridian planes of the naval structure of the funnel type (F), spaced at equal angular intervals.

Abstract: An antenna structure integrated in a hull or fuselage. The hull or fuselage can be the outer surface of an aircraft, artillery shell, missile or ship. The antenna structure includes an array antenna. The array antenna includes a number of antenna elements. Each antenna element includes a radiator and an RF feed. The antenna elements are arranged in a lattice within an antenna area including a central antenna area and a transition region outside the central antenna area wherein a number of the antenna radiators as well as resistive sheets are arranged in substantially the same plane as a surrounding outer surface of the hull or fuselage.

Abstract: A buoyant cable system and method is provided with a flexible towed platform that may be deployed into the water from a submerged submarine. The flexible towed platform has a memory that returns to a selected shape after deployment. A presently preferred selected shape may have one or more curves that provide a function during towing. For instance, in one embodiment two oppositely extending curves each float and each are pressed by the water in a balanced manner to provide a stable platform for one or more antennas which can be of different types suitable for a wide band of radio frequency reception/transmission. In another embodiment, a keel may be formed from a weighted curved portion that is suitable for vertically supporting an antenna. The flexible towed material may be constructed of coil springs, shaped memory alloys, and the like.

Abstract: A buoyant cable system and method is provided with a towed platform that is flexible for deployment into the water from a submerged submarine. The towed platform has a memory that returns to a selected shape after deployment. In one embodiment the biasing member is a spring acting against and anchored to Kevlar® strands running through the blocks such that the blocks are compressed into a desired shape during operation but remain sufficiently flexible for deployment and retrieval. In another embodiment, a keel may be formed from a weighted curved portion that is suitable for vertically supporting an antenna above the surface of the water to prevent signal interference due to water washing over the towed transmission line.

Abstract: A buoyant cable antenna element is taught that employs a specific double-negative meta-material sheath with a negative permeability. The double-negative meta-material sheath is disposed over the insulated wire portion of the buoyant cable antenna element. The double-negative meta-material sheath enables a deliberate reduction in the antenna wire inductance to a zero value at a desired critical frequency. Reducing the antenna wire inductance to zero creates a traveling wave structure antenna having enhanced bandwidth.

Abstract: Multifunctional structures and methods of manufacturing multifunctional structures which function as both electronic devices and load-bearing elements are disclosed. The load-bearing elements are designed to have electronic functionality using electronics designed to be load-bearing. The method of manufacturing the multifunctional structure comprises forming an electronic element directly on at least one ply of arbitrarily shaped load-bearing material using conventional lithographic techniques and/or direct write fabrication techniques, and assembling at least two plies of arbitrarily shaped load-bearing material into a multifunctional structure. The multifunctional structure may be part of an aerospace structure, part of a land vehicle, pan of a watercraft or part of a spacecraft.

Abstract: A buoyant cable system and method is provided with a towed transmission line and antenna platform that may be deployed into the water from a submerged submarine so that the antenna extends above the surface of the water. The cable system preferably utilizes a flexible weighted keel formed in a section of the transmission line. A buoyant section of transmission line extends upwardly from the depth of the weighted keel to support one or more antennas above the surface of the water. In another embodiment, a plurality of weighted keels may be formed in sections of the transmission line whereby an inverted U-shaped buoyant portion extends upwardly from the depth of weighted keel to act as the support for a horizontally oriented antenna.

Abstract: A vibration isolation system for the antenna of a vehicle, such as a maritime vessel. The vibration isolation system has a staged construction that slidably attaches the maritime antenna to a maritime vessel along up to three independent axes of translation. This staged construction is adapted for independently decreasing movement of the antenna along the independent axes of translation. Accordingly, the staged construction prevents the antenna from rotating due to induced translational vibration and thus enhances the pointing performance for the antenna.

Abstract: An modular, inflatable, multifunction, multipurpose, parabolic reflector apparatus having a plurality of manufactured parabolic mirrors made from a pressure-deformable reflective covering of an inflatable ring for focusing electromagnetic energy from radio frequency radiation (RF) through the ultraviolet radiation (UV) and solar energy for (1) heating and cooking, for (2) electrical power generation, for (3) enhancing the transmission and reception of radio signals, for (4) enhancing vision in low-light environments, and for (5) projection of optical signals or images. The device also has non-electromagnetic uses, such as the collection of water. A first main embodiment utilizes two reflective membranes. A second main embodiment utilizes a reflective membrane and a transparent membrane. Portability is enhanced by complete collapsing of the inflatable device.

Abstract: A device for controlling steering of a towed underwater object, in particular a towed linear acoustic antenna. The device comprises a body having a longitudinal axis, the body being provided with a fastener for fastening it releasably to the towed object, and a plurality of stabilizer fins, each of which is coupled to the body and extends along an axis that is transverse to the longitudinal axis of said body, the angular position of each fin relative to the body being pivotable about its transverse axis by control, so as to modify the angles of inclination of said fins.

Abstract: A system and method for automatically positioning an antenna aperture on a mobile platform in a manner to avoid blockages created by other components/subsystems on the mobile platform between the line of sight of the antenna aperture and a satellite and to avoid interference with other systems that share the mobile platform. In one embodiment, one or more linear support elements are moved by one or more corresponding motors to allow the antenna aperture to be re-positioned between a plurality of different positions. Methods for creating and using a blockage database are also disclosed.

Abstract: An underwater communication method is provided. EM signals are transmitted via a seabed using an underwater electrically insulated magnetically coupled antenna. By making use of the low loss properties of the seabed, EM signal attenuation can be reduced and consequently the transmission range can be increased. The underwater electrically insulated magnetically coupled antenna may be located within a body of water or may be buried in the seabed.

Abstract: A technique for boresighting an antenna mounted on a moving platform is described. The technique uses a concurrently moving calibration target. Target navigation data and platform navigation data are used to compensate for movement of the target and the platform. The antenna pointing direction is biased in a direction which provides a best signal quality, and the bias used to determine antenna boresight calibration factors. The boresight correction factors can be used for open loop pointing.

Abstract: The invention provides an antenna system for operation near a ground plane, for example, at or near the surface of a body of water. The antenna system includes, for example, an array of filar elements attached to one or more spiral elements. The system also includes, for example, a buoyant support and/or housing for transporting the antenna to and/or maintaining the antenna at or near the surface of a body of water.

Abstract: A speedometer and communication device for boats includes a hand-held GPS unit, mounting member and antenna ring. The mounting member has a flange that extends and secures the mounting member to a cavity located in the dashboard of the boat. The mounting member may further have a power plug to supply power and mounting posts to secure the hand-held GPS unit. The antenna ring contains a receiver for receiving GPS signals and a transmitter for re-sending GPS signals. The hand-held GPS unit receives, calculates, and displays data relating to speed, location, time and includes user-selectable buttons for contacting emergency services.

Abstract: The present invention involves an inflatable antenna system including an inflatable antenna and a mounting plate. The inflatable antenna includes an inflatable cone or cylinder and a plurality of conductors integrated therein. The mounting plate can be incorporated into a protective enclosure that holds and protects the inflatable antenna during transport, supports it during use, and provides a means for mounting it to a mast. The mounting plate serves as a mounting surface for the inflatable antenna, a radio frequency (RF) connector, an air intake valve, and an impedance matching network. Selected surfaces of the protective enclosure can be coated with conductive materials. An air intake valve allows for inflation and deflation of the inflatable antenna. Inflatable support members can be used in conjunction with a stabilizing portion comprised of a vertical member and attached weight, to allow the inflatable antenna system to be deployed in water.

Abstract: An antenna assembly for mounting on a backstay of a sailboat. An insulative support apparatus includes a slotted center tube that can be forced over the backstay for mounting thereon. First and second outer tubes are attached on opposite sides of the center tube for holding first and second elongated radiators. Proximal ends of the radiators are electrically joined together and to a lead in-wire for connection to a receiver and/or transmitter. Distal ends of the radiators are secured at distal ends of the outer tubes by attachment to eyelets on the bottoms of plugs inserted into the distal ends of the outer tubes, which serve additionally to prevent water from entering the tubes. The outer tubes each include a water drainage channel to allow moisture accumulating to run out a bottom, proximal end of each tube.

Abstract: An antenna linear extension and retraction apparatus and method of use for a submersible device is provided. The apparatus includes a body having a cavity formed at an external surface. A bladder containing a core material is arranged within the cavity. The core material contracts and expands the bladder depending upon a pressure that surrounds the bladder. An antenna is operatively connected with the bladder and moves between a retracted position and a deployed position as the bladder contracts and expands.

Abstract: A sea surface antenna comprises a cylindrical tube of metallic material 13 on a dielectric former. The tube has a longitudinal slot shorted at each end and coupled at its midpoint to a coaxial feed. The slot is bridged by two groups of capacitances each group being distributed along a respective half of the slot. The length of the antenna is less than 0.25 ? and the diameter of the antenna is less than 0.02 ?, where ? is the free space wavelength at the operating frequency. The antenna is dimensioned so as to operate in an evanescent mode at a resonant frequency less than the cut-off frequency.

Abstract: A remotely controllable, tiltable platform supports a radar transmitter/receiver for rotational movement of the radar relative to a mounting on a vessel, such as a mast of a sailboat or the superstructure of a power boat. A cowling extends upward from the foundation plate and a stationary hinge plate, parallel to the foundation plate, is secured to the top of the cowling. A top antenna mounting plate is hingedly secured to the stationary hinge plate. An actuator is positioned within the cowling to controlled movement of the top antenna mounting plate to maintain the radar level with the horizon. Alternatively, an A-frame structure mounts the leveling system to a mast of a sailboat.

Abstract: A light weight antenna system and corresponding lightweight transmission lines are disclosed that are characterized as having an extremely light weight relative to prior such systems and lines. An inflatable body having an inner surface connected to an outer surface with a plurality of support structures, such as connecting tubes. Antenna elements are disposed on the outer surface of the inflatable body to form, for example, a phased array antenna. Coaxial transmission lines are used to transmit signals to and from an antenna element and are, in one embodiment, created by disposing an inner conductor within the aforementioned connecting tubes. Such a transmission line may be utilized in a number of applications, such as to connect a base station to an antenna system of a wireless communications network. In another embodiment, quasi coaxial transmission lines are formed by disposing flexible membrane shields around a transmission elements.

Abstract: The mast device for a submarine comprises a guiding means, a vertically traversable mast guided therein and information means which are provided at the mast upper end and which are in electrical interaction with the inside of the submarine for emitting and receiving information. The information means are arranged in a buoyant unit held on the mast upper end without connection to this. The buoyant unit is fastened to a flexible coupling means which may be let out and retracted and which is of the length essentially of the maximum desired observation depth of the submarine.

Abstract: An apparatus including a gimbal and an antenna with a hollowed frustum having a closed end and an open end. The antenna includes a feed stem at the closed end extending as an internal rod into the hollowed frustum. The opposite end of the rod connects to a receiver section extending from an edge of the open end beyond a longitudinal axis of the antenna. The antenna is supported by the gimbal attachable to a container suitable for towing. A pivot at the open end in relation to the center-of-gravity of the frustum allows a swinging arc in relation to the attached gimbal in that the frustum moves by gravity toward the axes of the gimbal such that the receiver section maintains a facing position to the force of gravity.

Abstract: The mast device for a submarine comprises a guiding means, a vertically traversable mast guided therein and information means which are provided at the mast upper end and which are in electrical interaction with the inside of the submarine for emitting and receiving information. The information means are arranged in a buoyant unit held on the mast upper end without connection to this. The buoyant unit is fastened to a flexible coupling means which may be let out and retracted and which is of the length essentially of the maximum desired observation depth of the submarine.

Abstract: An antenna assembly for mounting on a backstay of a sailboat. An insulative support apparatus includes a slotted center tube that can be forced over the backstay for mounting thereon. First and second outer tubes are attached on opposite sides of the center tube for holding first and second elongated radiators. Proximal ends of the radiators are electrically joined together and to a lead in-wire for connection to a receiver and/or transmitter. Distal ends of the radiators are secured at distal ends of the outer tubes by attachment to eyelets on the bottoms of plugs inserted into the distal ends of the outer tubes, which serve additionally to prevent water from entering the tubes. The outer tubes each include a water drainage channel to allow moisture accumulating to run out a bottom, proximal end of each tube.

Abstract: A slotted antenna comprises a plurality of loop structures and interconnecting conductors that define a slot. The antennas can operate in a single band or over multiple bands. Flexible or inflatable substrates enable easy storage aboard an underwater craft and facilitate deployment and towing behind an underwater craft with minimal chances of detection.

Abstract: An antenna including a feed tube with radial fins and circular plates at the ends of the tube and fins thereby forming a boundary for a plurality of resonant cavities. Curved plates, connected to the tube by switches of a switching system, partially encompass and subtend to the length of the tube. Interior to the tube, a transmission line from an end plate terminus conducts radio-frequency energy from the terminus to a hub and onto a switch of the switching system in which the switch is mechanically reactive to and actuated by a righting action of the curved plates when the curved plates encounter a sea state. When actuated, energy from the switch distributes to a proximate resonant cavity and curved plate to form a radiation pattern based on the difference in phase of the resonant cavity and curved plate.

Abstract: Integrated antenna coupler element, in particular for a multiband terminal of a mobile radio system, with an operating voltage connection, an antenna input/output, a transmit signal input, a received signal output, a transmit/receive control signal input, a required transmit power input and a control voltage transmit output stage output.

Abstract: A collision avoidance system mountable on an aircraft for providing to the pilot of that aircraft an early warning of the presence of another nearby threat aircraft within the surrounding air space. The system operates autonomously from that aircraft and does not require the presence of any matched system on board the threat aircraft. The system includes an omni-directional L-band microwave antenna formed by a dielectric sphere cut into eight equal “orange wedge” sectors covering eight distinct beam patterns. Eight L-band microwave signals are transmitted simultaneously from all eight dielectric sectors to provide a sphere of detection around the aircraft. The sectors also act as receivers for detecting a microwave signal reflected back from the threat aircraft, and indicating means provides information to the pilot regarding the direction, closeness and rate of closure of the threat aircraft.