 for transportation. Cost is the main driver for small Earth station antennas for mass-market applications. Receive-only terminals in the 4/6-GHz band for data or TV reception are usually symmetric prime-focus paraboloid; they are made by spinning an aluminium sheet. In the 11-GHz communication band or the 12-GHz DBS band, prime-focus offset reflectors made from fiberglass molds are popular. A simple open-ended waveguide feed is incorporated on a sturdy feed support with the first-stage low-noise, converter incorporated directly into the feed. There is considerable interest in making flat-plate array antennas that can be mounted flush against buildings and that incorporate electronic scanning to receive the satellite signals. The technology for electronic scanning is available from military radars but not, far, at a price that is acceptable to the domestic market. Satellite Antennas for Telemetry, Tracking, and Command The ideal Telemetry, Tracking, and Command (TT&C) antenna would give omnidirectional coverage SO that the orientation of the satellite is irrelevant. Wire antennas are used for VHF and UHF coverage, but the spacecraft is a few wavelengths across at these frequencies and therefore considerable interaction between the antenna and the satellite distorts the radia- tion pattern. An alternative approach is to use a low-gain antenna to provide full Earth coverage. This is particularly useful for spin-stabilized spacecraft. The earth subtends 17 degrees from a geostationary satellite, which can be met with a small conical horn. Spot Beams Spot beam antennas are required to produce a beam covering a small region of the Earth's surface. The angular width of the beam is inversely proportional to the diameter of the antenna. Size considerations virtually dictate that some form of deployable mechanism is needed on the satellite, and this leads to the use of offset reflectors with a dual-mode or corrugated feed horn. The constraints of the launcher mean that the maximum size for a solid reflector is about 3.5 m