Abstract: An antenna system utilizing an electrically conductive portion (16) of an aircraft structure to radiate and receive very-high-frequency (VHF) and ultra-high-frequency (UHF) radio signals over a wide frequency range without the need for an active tuner to accommodate frequency changes. An antenna element (22) is housed in a tail fin endcap section (20) and is positioned and shaped to form an elongated notch (26) between one edge (24) of the element itself and one adjacent edge (18) of an electrically conductive tail fin (16). The notch (26) is uniform over part of its length and is flared to a wider spacing over the remainder of its length. A feed point (30) along the notch (26) is selected for optimum performance. Matching electronics (14) couple the antenna system to a transceiver (15), which can operate either in a VHF/FM band, or in a UHF band, or in a VHF/AM band. The antenna system provides relatively good gain over the frequency range and provides a practically omnidirectional radiation pattern.

Abstract: In the preferred embodiment of the invention, a broadband dipole antenna 10 for transmitting and receiving electromagnetic energy constructed of coaxially aligned radiating elements 14 and 16 is provided. Each of the radiating elements 14 and 16 has a charge collector 40 and 42 affixed to its free end, that function to collect charges forming a current sink for collecting the current generated by the radiating elements. Coupled with the radiating elements is an isolation choke 44 to isolate the radiating elements against electrical disturbances caused by the antenna support platform 130 and 138 effecting a match of the impedance between the radiating elements and the transmission lives. Another preferred embodiment is a monopole 86 equipped with a charge collector 96. The dipole 10 and monopole 86 are provided pairs of open-sleeves 28 and 26 and 92 and 94 to enhance the instantaneous bandwidth of the radiating elements.

Abstract: A compact high frequency multi-turn loop antenna is provided for use on a conductive structure such as the airframe of an airborne vehicle. The antenna employs a plurality of interconnected conductive loops which are magnetically coupled to a conductive structure. One end of the conductive loops is coupled via tuning and impedance matching circuits to a transceiver for transmitting and receiving signals therefrom. The other end of the conductive loops is coupled to ground. When transmitting a signal, the transceiver excites a current on the conductor which induces a magnetic field that excites the conductive structure. Upon receiving a signal, the conductive structure is excited which in turn generates a magnetic field through the plurality of loops and induces a current on the conductor. The antenna may advantageously be mounted within a conductive cavity structure which in turn is connected to the conductive structure.

Abstract: A generally planar antenna structure having at least six radial antenna elements, each of which uses log-periodic principles to provide a broad bandwidth of operation. Each antenna element has a radial arm and integral, arcuate teeth extending in opposite directions from the radial arm, such that the spacing, width and length of the teeth increases with increasing radial distance from the center of the structure. The teeth are preferably interleaved with teeth in adjacent antenna elements. A feed region of the structure is provided near its center, to connect the antenna elements through a connection matrix to input/output terminals and provide operation in multiple modes and multiple polarization senses.

Abstract: A plurality of dual feed half square wave antenna element (each of U-shaped onfiguration) are arranged in a log-periodic structure. The antenna elements are feed at the current loops; i.e., at the corners of the U-shaped antenna elements. A dual inphase feed produces vertical polarization signals of low angle radiation, and a dual antiphase feed produces horizontal polarization signals of high angle radiation.

Abstract: Two cosited omnidirectional biconical antennas are respectively tilted plus nd minus 45 degrees (.+-.45.degree.) with respect to the vertical and, therefore, are perpendicular (90.degree.) with respect to each other to effect polarization mismatch and near field decoupling. In combination with the described antennae orientation, high impedance cable chokes are added in series with the coaxial cable antennae feed lines to suppress induced parasitic rf currents.

Abstract: A vertically polarized array comprised of both bottom fed and top fed conurations having a driven element comprising at least one but, when desirable, two generally horizontal wire conductor segments of a length substantially equal to one half the operating wavelength of the array and with the ends of the half-wave conductor segments being connected to or extending into generally vertical quarter wavelength wire conductor segments. In a bottom fed configuration the feedpoint is at the bottom end of one vertical quarter wavelength conductor segment while in a top fed configuration one vertical quarter wavelength segment comprises a quarter wavelength of coaxial transmission line having one end configured into signal isolation means, comprising a cable choke, while the feedpoint is located at the other end.

Abstract: A high voltage protection device for protecting personnel from injury or th as well as damage to radios and vehicles when a whip antenna comes in contact with overhead high voltage power lines or the like and comprises a high voltage coaxial capacitance device which is coupled in series between the upper and lower section of a whip antenna. The capacitive reactance of the capacitance device is very high at power line frequencies and relatively low at RF frequencies. The capacitance element is comprised of two concentric cylindrical conductors formed in a fiberglass shell and separated from one another by a dielectric such as polytetra fluorethylene.

Abstract: A VHF monopole antenna unit, particularly adapted for operation in the 30 MHz frequency range, yet capable of embodiment in a compact structure only approximately 11/2 feet in height is described. Coarse tuning is accomplished in a number of switched bands, for each of which is provided a specially designed matching network comprised of inexpensive L-networks of inductors and capacitors. Tuning is accomplished through adjustment of inductor elements. The simple, inexpensive design of the matching circuits eliminates need for intricate mechanisms typically used for automatic impedance matching over a wide band and also for a broadband impedance matching transformer. The compactness made available by the unique top-load structure design is further made possible by provision of a specially designed dielectric filled vertical antenna element, accomplishing the same range and efficiency in an even more compact antenna.

Abstract: A unitary broadband high impedance isolation section for a plurality of cely spaced antennas as well as other electrical apparatus wherein the respective separate coaxial cables feeding the antennas and the shielded multi conductor cable for the other electrical apparatus are wound in the same direction on a common core and have the same number of turns, with the shields or outer conductors of all the cables being respectively connected together at the beginning and the end of the windings. The multiport cable choke thus configured can be provided with respective connectors at each end of the choke for facilitating ease of installation into the electrical system, that is, a single multiport cable choke can be inserted in the feed lines of multiple antennas and other electrical equipment simply by means of making suitable interconnections by way of the connectors on both sides of the multiport cable choke assembly.

Abstract: A phase front homing system airborne antenna array which employs portions the airframe as two antenna elements and wherein each antenna element includes a coaxial sleeve coupler.

Abstract: A center-fed VHF dipole antenna structure particularly adapted for 30-80MHz peration wherein one half of the radiating structure comprises the outer conductor of a coaxial feedline which includes a low-loss cable choke at the lower end of the half dipole length of the feedline while the other half of the dipole consists of a conventional radiating conductor element. Additionally, remotely controlled variable impedance elements are included at the feedpoint to provide selective coarse and fine tuning of antenna resonance.

Abstract: A VHF radio frequency antenna for a homing receiver suited for airborne aications and comprising a pair of right angled antenna elements of like configuration terminating in a common non-conductive joint of insulator material while their opposite ends terminate in dielectric supports mounted on an electrically conductive ground plane such as an aircraft skin. The ends of the elements terminating in the dielectric supports additionally connect to signal coupling means which feed to a homing receiver or other utilization device through equal length transmission lines.

Abstract: A phase front homing system airborne antenna array employing portions of airframe as two antenna elements.

Abstract: An isolation system adapted to permit simultaneous operation of at least colocated radio transceivers operating at different frequencies into at least one antenna by means of a single hybrid transformer having said at least one antenna coupled to one conjugate port, at least one broadband impedance simulator coupled to the other conjugate port and wherein said transceivers are respectively coupled to sum and difference ports of the hybrid transformer.

Abstract: A broadband isolation section comprised of a plurality of series connected able chokes having respective damping resistors shunted thereacross located between at least two dipole antennas mounted one above the other in a generally vertical plane. The isolator section is particularly adapted to be utilized with dipole antennas having respective pairs of radiating elements substantially aligned in a common vertical axis and being fed from respective radio signal sources by feedlines directed along the common vertical axis through the various radiating elements. The cable chokes included in the isolator section are formed from coaxial cable feedlines and the respective damping resistors shunted thereacross are connected to the sleeve or outer conductor of the feedline(s) feeding the upper antenna(s). Thus adjacent antennas have intermediate broadband isolator sections separating them.