CONICAL SCANNING ANTENNAS

Seavey Engineering designs custom tracking antennas including conical scanning types. The following are examples of high-performance antennas using the conical-scanning principal. In many Seavey Engineering designs, conical scanning is accomplished by the mechanical rotation of a "subreflector" located in front of the focus of the reflector. The feed system has a modified Cassegrain geometry with the feedhorn located between the reflector vertex and the subreflector. The beam nutation is accomplished without RF rotary joints so that power handling capability remains high and there is no wow or noise generated by the scanning system. Overall radiation pattern performance is excellent; crossover levels of about 1 dB are found to give good tracking performance. Radiation pattern performance can be accurately predicted; resulting sidelobes are found to be in good agreement with analyses. The scanning mechanism is fully integrated, sealed against the environment and may be readily accessed for maintenance purposes.

Model 8522-800 - 3 foot C-band Conical Scanning Antenna This antenna uses a 36 inch diameter parabolic reflector operating in the 5.4 - 5.9 GHz frequency band with vertical polarization. The antenna conically scans at a rate of 1800 RPM and has a sine/cosine resolver angle output. The feed is a pressurized and sealed modified horn having a polyrod extension for beam narrowing purposes. It handles 1 megawatt peak power and 1 kilowatt average power. Crossover level is 1 dB and gain is 31 dBi. The waveguide port is WR-187 waveguide located at the rear of the reflector.

Model 8522-800 3-foot C-band

Model 9133-800 - 6-Foot C-Band Conical Scanning Antenna Designed for use in the 4.4 - 5.0 GHz frequency band, this 6-foot vertically-polarized antenna has a gain of 36 dBi with a crossover level of 1.0 dB. It weighs 65 pounds. The 3 dB beamwidth is 3.6°. The horn feed’s pattern is shaped with a polyrod. An 1,800 RPM hysteresis-synchronous 115 VAC 60 Hz motor rotates the tilted 8" diameter hyperboloidal subreflector. A size 11, 26-volt resolver is used. Model 9133-800 6-foot C-band

Model 8522-802 - 12-foot X-band Conical Scanning Antenna This antenna utilizes a 12-foot diameter aluminum parabolic reflector, four dielectric subreflector support spars, a high power polyrod feed and a rotating, tilted flat plate which functions as a rudimentary Cassegrain subreflector. It operates in the 9100 - 9400 MHz frequency range with linear polarization. Crossover level is 0.9 dB, gain is 48.1 dBi, beamwidth is 0.62° and sidelobes are better than 20 dB down. The scanning mechanism permits scan rates of either 300 or 1800 RPM (remotely selectable) and the angle output is a simple AC generator giving 26 volts output at the maximum scan rate. The antenna is rated at 2 megawatts peak power; feed pressurization is 10 psig.

Model 9465-830 2-foot Ku-band

Model 9465-830 - 2-Foot Ku-Band DSS Conical Scanning Antenna This small antenna has been designed for DSS Satellite TV applications. It provides enhanced pointing capability for DSS systems which are dynamically stabilized on moving vehicles such as RVs and boats. It uses a vertex-mounted "splash-plate" feed. The tilted plate rotates by means of a plastic sleeve outside the circular waveguide feed tube. This antenna includes a standard 12.2 - 12.7 GHz dual low-noise Block downconverter and is directly compatible with all standard DSS TV receivers. A simple LED sensor gives angular position information. A belted DC motor rotates the beam about 1500 RPM. Crossover level is about 0.4 dB.