SPECIAL DUAL BAND FEEDS

Seavey Engineering develops more than one hundred special purpose antennas each year. Our company delivers innovative solutions to your antenna problems. Your particular antenna requirements will be quickly addressed by our engineering staff.

The following shows examples of some of the design problems given to us and our response to the specification requirements. In all cases, the technical solution was done in a "quick-reaction" time frame of several days to several months.

Model 8942-800 - Dual frequency (1200 & 3100 MHz) feed with coincident phase centers
A dual frequency (1200 & 3100 MHz) feed with coincident phase centers; 30 dB maximum cross-polarization and antenna sidelobes better than 22 dB down. The structure is optimized for minimum primary pattern interaction and best isolation. Polarization and frequency band switching was provided with a remotely-actuated coaxial switch.  The delivered antenna is being used as part of antenna range instrumentation for testing modern radars.
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Model 8942-800
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Model 8365-800

Model 8365-800 - UHF Feed for Existing Reflector
Requirements specified that the antenna would be an existing 5-meter diameter reflector and that the feed should have vertical polarization in the 200 - 300 MHz band and horizontal polarization in the 300 - 400 MHz band. The design also allowed the feed to mount easily to the vertex of the reflector.A set of broadband dipoles was attached to a metal support spar. Tuned reflecting elements optimized the primary patterns. Coaxial cables were led from each dipole feed point to the base of the spar support, where a coaxial switch was installed for bandswitching. The completed feed was tested in the 5-meter reflector. 
 

Model 9836-800 - Special Prime-Focus Dual-band Feed for 60-foot Reflector
The 225 - 400 MHz low band is dual circular polarized and is rated at 2KWCW. The 1.2 - 1.6 GHz high band is circularly polarized to receive both L1 and L2 GPS signals. Both bands have coincident phase centers.

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Model 9836-800

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Model 9802-800

 Model 9802-800 - Dual-band Monopulse Feed for 4.5M Axisymmetric Reflector
The 1.452 - 1.492 GHz downlink feed receives Worldspace satellite signals and incorporates a five-element monopulse circuit. The 7.025 - 7.075 GHz uplink feed is circularly polarized and handles 500 watts CW. The monopulse circuit allows the antenna to accurately point to the satellite using the downlink signal null. Both feeds have coincident phase centers.

 
Model 9821-800
Similar in function to Model 9802-800, except for 2.4M and 3.8M offset reflectors.

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Model 9821-800

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Model 8536-800

 Model 8536-800 - Dual Frequency and Constant (same) 
Beamwidth Cassegrain Feed System
The customer requirement was for a replacement feed system for a 40-foot precision antenna. The new application demanded that the antenna have the same beamwidth at 5 GHz and 15 GHz. A special concentric feedhorn was developed and delivered. It used the existing Cassegrain subreflector, but under-illuminated the subreflector at 15 GHz and defocussed the 15 GHz phase center.  The resulting antenna was used in a series of tropospheric scatter propagation studies.
Model 9014-800 - High G/T Telemetry Feed System
Used with an accurate 24-foot reflector, this feed system was specified for demanding G/T performance. The feed system included a broadband (400 - 500 MHz) turnstile-type radiating element in a cavity.  Two 1 dB noise figure Low-Noise Amplifiers with 30 dB gain are provided in each feed output channel. RF filters are also provided to reject strong on-site VHF communications and S-band radar signals. A BIT signal injection probe is placed within the feed cavity so that the receive chain components could be calibrated and verified. 

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Model 9014-800

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Model 9702-800

Model 9702-800 - A Special-purpose,
Coaxial-Aperture Dual-band Feed
The low-band is 1.665 - 1.700 GHz and is right-hand circular polarized. The high-band is the DSS band of 12.2 - 12.75 GHz. The feed is designed to interface with the circular waveguide port of standard DSS LNBs. This prime focus feed enables the antenna to receive all DSS entertainment signals and to receive all weather imagery signals at L-band.
Model 9702-820 - A Special-purpose, Coaxial-Aperture Dual-band Feed
The low-band is 1.525 - 1.661 GHz and is right-hand circular polarized. The high-band is the DSS band of 12.2 - 12.75 GHz. The feed is designed to interface with the circular waveguide port of standard DSS LNBs. This prime focus feed enables the antenna to receive all DSS entertainment signals. The low-band port interfaces with INMARSAT, AMSC and other communications satellites.

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Model 9702-820