TURRET MULTIBAND FEED SYSTEMS

To fully utilize large reflector antennas, broad frequency coverage is necessary. One alternative is to employ extremely broadband feeds and to switch communications bandwidth receiving components as necessary. This method results in compromises in performance. Inefficient illumination and focusing of very broadband log periodic feeds and losses in switching circuits and components reduce gain.

An attractive alternative, which has been thoroughly developed by Seavey Engineering, is the use of optimized prime focus feeds which are mechanically indexed to the focus of the reflector. Feeds are optimized by the proper specification of operating frequency band, polarization characteristics, LNA compatibility, and feed primary pattern shaping to achieve maximum antenna system G/T.

When feeds have been selected, they are placed on a mechanical "turret" which uses linear motion technology to remotely position each feed accurately at the reflector focus. In this manner, the antenna can be reconfigured in seconds from one mission to another without performance compromises and without having to physically change feeds.

Multiband Turret Feeds may be used with any reflector. They have particular use as retrofits into existing antenna systems in the 30 to 100-foot diameter class. They are considerably less costly than Cassegrain systems having fixed Cassegrain feedhorns and remotely positioned subreflectors.

The turret mechanism uses a precision lead screw and DC motor drive. A controller senses factory-set optical indices accurately positioned to each feed’s phase center. The controller may be commanded directly by manual push button control, or by an RS-232 data bus. The feed system controller always indicates feed status. Optional local control pendants can be supplied for use at the reflector.

Each Multiband Turret Feed System is custom configured with specified feeds. The following chart shows typical examples of this technology.

We can design and produce many other feed combinations to meet your requirements.

Model 8827-800 3-bands

Model 8859-800 9-bands

Model 8860-800 3-bands

Model 8917-800 3-bands

Model 8948-800 3-bands

Model 9015-800 3-bands

Model 9123-800 4-bands

NOTES: 1) Polarization switch included for each band. Also included is a bandswitch after the LNAs so all output signals are switched to a single RF port 2) Local control pendant and status indicator supplied for installation at reflector.