Abstract: An automatic radio direction finding system having inputs for a circular array with a plurality of directional antennas, each being switched in sequence producing a directional pattern in azimuth. The combined RF signal is carried through the receiver as a normal AM modulated signal and the intermediate frequency output of the receiver is detected and the added modulation is recovered, filtered, and accumulated in such a manner that random signals will cancel and any repetitive signals will increase in amplitude and be stored. The vector information of this stored modulation, when decoded with respect to the phase of the original modulation, contains the actual bearing information. The signal is then averaged over several cycles and displayed on a numerical readout in degrees azimuth. The averaging techniques are employed to eliminate jitter in the last digit.

Abstract: This cavity-backed top-loaded annular slot directional antenna is particularly well suited for radio direction-finding applications. Its unique properties allow it to be flush mounted for camouflage use with three or more symmetrical outputs which may be sampled continually. Each output has a symmetrically related unidirectional beam pattern and is nearly constant in impedance. The radio frequency voltages at these outputs are symmetrically phase related, and when combined they produce a circular pattern. All of the antenna elements are in a single structure and the combined outputs are extremely uniform, thus producing reliable patterns such that amplitude comparison for radio direction-finding purposes will be of good accuracy. A single cardioid pattern can be obtained by simply terminating the other ports in a matched load. In this form the antenna would be well suited for use as one antenna in a large aperture array.

Abstract: A three input device which accepts signals from a two port antenna system having opposing cardioid patterns, and a third input for a figure eight pattern that is at right angles to the first cardioids. The first antennas cardioids are combined by a zero-phase hybrid combiner into an omnidirectional pattern. This omnidirectional pattern is combined in a second hybrid combiner with the figure eight pattern so that the sum and difference patterns are present at the outputs. These signals are fed to a processor which decodes the front/rear directional information. To decode left/right directional information, switches bypass both hybrid combiners and feed the first antennas basic cardioid patterns directly to the processor.

Abstract: A plurality of antennas attached to the glass of the rear window of a vehicle produces patterns that may be combined to give directional pick up patterns. The first basic antenna is two spaced vertical whip antennas connected by parallel horizontal delay lines. Each whip output has a cardioid pick up pattern in the direction of the other antenna, in this case to the right and left. The second antenna is connected vertically across the window opening. Its output has a figure eight pick up pattern, typical of a slot antenna, with the lobes to the front and rear of the vehicle. The phase relationship of these three pick up patterns are such that if properly combined, then either of two sets of pick up patterns can be obtained. The first pattern is the basic right and left cardioid, and the second pattern is the front and rear cardioids. When used in combination with a communications receiver and processor, the direction of the transmitter can be determined, regardless of which quadrant it lies.

Abstract: A yagi antenna having a director element, a half-wave active dipole element, and a reflector element mounted on an antenna boom. All antenna elements are rods that are telescopically adjustable in length from a collapsible position to an operating length for a predetermined frequency of operation, and removable from threaded mounting for storage. The director element and reflector element are slidably adjustable on the antenna boom for independent spacing with respect to the half-wave active dipole element. The antenna boom has two mast support holes; one for horizontal polarization and the other for vertical polarization. A ferrite core member surrounds a coaxial cable connecting the half-wave active dipole element to a coaxial connector, and provides balun action between the coaxial cable and a balanced antenna feed point.

Abstract: A Mobile Directional Comparator (MDC) used in combination with a communications receiver to process received signal information from a two port antenna system to drive a directional indicator. A radio frequency modulator modulates two received cardioid antenna signal patterns with two low frequency sine wave signals at a low modulation percentage and out of phase with each other. The two modulated cardioids are then combined in a hybrid circuit to produce a non-directional radio frequency signal pattern with respect to the antennae center axis. The combined modulated rf signal is carried through the receiver as a normal signal, and the intermediate frequency output of the receiver is processed by a phase demodulator in the MDC to extract from the signal phase and amplitude information to drive the directional indicator.

Abstract: An Isolation Differential Combiner which accepts signals from two spaced vertical whip antenna elements and which are then combined through delay lines so that the resulting said reception pattern is a cardioid signal pattern at the combiner outputs. The isolation of the two signals is accomplished by connecting wide-band balanced transformers as hybrids. The differential component of the two signals present at the hybrid combiner is available at each secondary winding of each wide-band balanced transformer.

Abstract: A cavity tuning assembly for use in a tuned cavity having provisions for coarse tune adjustment and fine tune adjustment for changing the frequency of the cavity's resonance. Coarse tune adjustment is obtained by sliding an unthreaded cavity tuning rod of the cavity tuning assembly up and down through a threaded bushing to obtain rough tune whereupon the unthreaded rod is locked into place by way of a knurl nut compressing a split end portion of a shaft lock screwed onto the threaded bushing into friction engagement around the cavity tuning rod. Fine tune adjustment is obtained by rotating the unthreaded rod into engagement with the shaft lock and the threaded bushing causing the threaded bushing and engaged structure to screw into or out of a pipe reducer to obtain fine tune which is then locked against the threaded bushing by a lever lock nut.