A 2.2 GHz IceConeFeed in a 3 m prime-focus dish for LEO tracking

A customer operates a rooftop ground station for S-band LEO downlinks in the 2200–2290 MHz space-operations band. The reflector is a KTI/SAMI SI 10: a 10 ft (3.05 m) aluminium mesh dish from Judsonia, Arkansas, built in the US home-satellite era. The original installation manual came with it: prime focus, focal length 45 5/8 in (1159 mm), f/D 0.38. It was built for C-band TV at 4 GHz, so the mesh is a solid reflector at 2.2 GHz. The dish sits on an az/el rotator and follows LEO passes.

3 m KTI/SAMI mesh dish with a 2.2 GHz IceConeFeed at the prime focus — The SAMI SI 10 with the new feed at the prime focus.

Close-up of the expanded-aluminium mesh of the 3 m SAMI dish, with the 2.2 GHz IceConeFeed visible through it — The mesh up close, feed behind it. At 2.2 GHz the aperture spacing is a small fraction of a wavelength, so the mesh acts as a solid reflector.

The task was the feed. The IceConeFeed is designed for 2.4 GHz and an offset dish; for this installation we built a customised unit tuned to 2200 MHz (IceConeFeed Customized, 2200–2500 MHz on request), with the turn count chosen to illuminate a deep prime-focus reflector: at f/D 0.38 the rim sits 67° off axis seen from the feed. Measured before shipping: SWR < 1.1 at 2200 MHz.

IceConeFeed radome and LNA housing at the prime focus, side view — Feed from the side: printed radome toward the dish, LNA and filter housing behind it.

Mechanically the feed drops into the original SAMI feed plate. A 3D-printed adapter plate (PETG) carries the IceConeFeed base and bolts to the four SAMI studs; the N connector faces the rear of the plate, where a short pigtail runs into the black cylinder behind the feed. That cylinder is a radome housing the LNA and band filters right at the feed, so the noise figure is set before the long coax down the mount.

3D-printed adapter plate on the SAMI feed plate with the feed pigtail — The adapter plate on the SAMI feed plate, pigtail to the LNA housing.

IceConeFeed and adapter plate seen from below the dish — Feed and adapter seen from below.

Front view of the mesh dish with the feed at the focus — Front view: the feed at the focus, radome toward the reflector.

Hub plate of the SAMI dish, Made in the USA — The original hub plate.

The dish slewing in elevation on its az/el mount:

Eight seconds of an elevation slew.

If you have an old C-band mesh dish and want to use it for S-band or L-band satellite work: the geometry is the same problem, and we tune the feed to your frequency. Get in touch.