Abstract: A microwave antenna for transmitting and/or receiving electromagnetic waves of at least one predefined frequency and a predefined polarization, the antenna comprises a support with upper and lower faces; at least one pair of substantially identical upper and lower radiating elements disposed on said upper and lower faces; in each pair of said radiating element in the upper face and the corresponding radiating element in the lower face, the phase center of the lower radiating element substantially coincides with the phase center of the upper radiating element.

Abstract: A microwave antenna for transmitting and/or receiving electromagnetic waves of at least one predefined frequency and a predefined polarization, the antenna comprises a support with upper and lower faces; at least one pair of substantially identical upper and lower radiating elements disposed on said upper and lower faces; in each pair of said radiating element in the upper face and the corresponding radiating element in the lower face, the phase center of the lower radiating element substantially coincides with the phase center of the upper radiating element.

Abstract: A conduction cooled electronic card module is designed for insertion into a chassis of an electronic device so as to transfer thereto a heat generated by electronic components of the module. The module comprises a circuit card of a convection cooled type, and a thermally conductive frame carrying the circuit card. The circuit card has a front surface carrying at least a part of the electronic components, and a rear surface at least edge areas of which are adapted to be in thermal contact with the chassis. The frame is in thermal contact with the part of the electronic components and with the front surface of the circuit card at least at edge areas thereof, so as to conduct heat generated by the electronic components, via the edge areas of the front surface to the edge areas of the rear surface of the circuit card.

Abstract: A fluid impeller, such as a fan for moving air or gases, includes one or more rotatable fluid impelling blades; a flow guiding member adjacent to an edge of the blades, and at least one blade facing surface of the flow guiding member being formed substantially as a segment of a sphere of radius r1 about a center of curvature. Each blade has a flow guiding member abutting edge curved substantially to fit against a sphere of radius r1.

Abstract: A conduction cooled electronic card module is designed for insertion into a chassis of an electronic device so as to transfer thereto a heat generated by electronic components of the module. The module comprises a circuit card of a convection cooled type, and a thermally conductive frame carrying the circuit card. The circuit card has a front surface carrying at least a part of the electronic components, and a rear surface at least edge areas of which are adapted to be in thermal contact with the chassis. The frame is in thermal contact with the part of the electronic components and with the front surface of the circuit card at least at edge areas thereof, so as to conduct heat generated by the electronic components, via the edge areas of the front surface to the edge areas of the rear surface of the circuit card.

Abstract: A conduction cooled electronic card module is designed for insertion into a chassis of an electronic device so as to transfer thereto a heat generated by electronic components of the module. The module comprises a circuit card of a convection cooled type, and a thermally conductive frame carrying the circuit card. The circuit card has a front surface carrying at least a part of the electronic components, and a rear surface at least edge areas of which are adapted to be in thermal contact with the chassis. The frame is in thermal contact with the part of the electronic components and with the front surface of the circuit card at least at edge areas thereof, so as to conduct heat generated by the electronic components, via the edge areas of the front surface to the edge areas of the rear surface of the circuit card.

Abstract: When prospecting for geological formations, a feeding electrode 2 is grounded in the centre of a circle formed by uniformly grounded feeding electrodes 3. The feeding electrodes 3 are connected by lengths of supply lines 4 to current generators 1 via regulators 5. A first stage of investigations involves a preliminary sounding. Current pulses are applied from the generators 1 to the lengths of supply lines 4 which are connected to diametrically opposite feeding electrodes 3. A current pulse period is synchronized with a reference signal received by a receiver 7 from the global radio navigation system. Upon turning the current off, a signal of a field magnetic component transient is measured by a meter 8 that is coupled to a magnetic component sensor 9.

Abstract: A multi-antenna element in the form of a narrow strip and including a dielectric substrate in the form of a narrow strip, a substantially continuous thin metallic layer coated onto one side of the dielectric substrate, at least one generally elongated discrete thin metallic layer coated onto the other side of the dielectric substrate and containing within its surface at least one void of predetermined location, size and shape, and each such void present in said discrete layer containing therewithin in noncontacting and in substantially coplanar relationship with the discrete layer at least one further discrete thin metallic coated layer of predetermined location, size and shape.

Abstract: A gyrotron backward wave oscillator device is described which can be operated in a controlled and predictable manner. The device includes an evacuated waveguide section, an electron source at one end providing a spiral electron beam, a collector at the opposite end, means for producing a magnetic field parallel to the longitudinal axis of the waveguide section, and an output window, the parameters of the device being such as to support backward wave oscillation therein and to output same through the window.

Abstract: An electron gun producing a spiral electron beam for gyrotron devices comprises means for producing an axial magnetic field propagating the beam axially beyond the anode of the electron gun, and separate electromagnets for producing a transverse "kicker" electromagnetic field beyond the anode and perpendicular to the magnetic propagation field such as to apply a transverse impulse of short duration, imparting a transverse motion, to the electrons to cause them to spiral as they are propagated axially beyond the anode.

Abstract: A cutter for a lawn mower has a rotating disc for mounting on a driving mechanism, the disc having a cavity therein and two openings at diametrically opposite points in the periphery of the disc and opening out of the disc from the cavity. A guide member is provided on the opposite side of the each opening and each pair of opposed guide members defines the opening therebetween. The disc has holes therein inclined outwardly from a surface of the disc other than the periphery and extending into the cavity, one hole being provided adjacent each of the openings. A plurality of flexible wire-shaped cutting members, each having a wire-shaped portion of a flexible material and a stop on one end thereof, extending through the inclined holes and through the cavity and out through the openings and project beyond the periphery of the disc, with the stops against the surface of the disc for preventing the cutting members from being flung outwardly of the disc during rotation thereof.