SATCOMM ANTENNAS

The antennas shown in figures 2-27 and 2-28 are used for satellite communications. The 0E-82C/WSC-1(V) antenna (figure 2-27) is used with the AN/WSC-3 transceiver and designed primarily for shipboard installation. Depending upon requirements, one or two antennas may be installed to provide a view of the satellite at all times. The antenna is attached to a pedestal. This permits the antenna to rotate so that it is always in view of the satellite. The frequency band for receiving is 248 to 272 MHz and for transmitting is 292 to 312 MHz.

The AN/SRR-1 receiver system consists of up to four AS-2815/SSR-1 antennas (figure 2-28) with an amplifier-converter AM-6534/SSR-1 for each antenna. The antennas are used to receive satellite fleet broadcasts at frequencies of 240 to 315 MHz. The antenna and converters are mounted above deck so that at least one antenna is always in view of the satellite.

The newer satellite systems use the SHF band. One of the major advantages of these systems is that they use a very small parabolic antenna measuring only 12 inches in diameter.

A satellite antenna must be pointed at the satellite to communicate. We must first determine the azimuth (AZ) and elevation (EL) angles from a fixed location. Figure 2-29 illustrates how these angles are derived,

Figure 2-29.-Equatorial Satellite Antenna Pointing Guide.

using a pointing guide called the Equatorial Satellite Antenna Pointing Guide. This guide is normally available through the Navy Supply System.

The antenna pointing guide is a clear plastic overlay, which slides across a stationary map. It indicates AZ and EL angles in degrees to the satellite. The values obtained are useful to the operator in setting up the antenna control unit of a satellite system.

To use the guide, follow these procedures:

1. Center the overlay directly over the desired satellite position on the stationary map.

2. Mark the latitude and longitude of the ship on the plastic antenna pointing guide with a grease pencil.

3. Determine the approximate azimuth angle from the ship to the satellite.

4. Locate the closest dotted line radiating outward from the center of the graph on the overlay in relation to the grease dot representing the ship's location. This dotted line represents degrees of azimuth as printed on the end of the line. Some approximation will be required for ship positions not falling on the dotted line.

5. Determine the degrees of elevation by locating the solid concentric line closest to the ship's marked position. Again, approximation will be required for positions not falling directly on the solid elevation line. Degrees of elevation are marked on each concentric line.

Example: Assume that your ship is located at 30 north and 70 west. You want to access FLTSAT 8 at 23 west. When we apply the procedures above, we can determine an azimuth value of 115 and an elevation angle of 30.

RHOMBIC ANTENNA

The rhombic antenna, usually used at receiver sites, is a unidirectional antenna. This antenna consists of four long wires, positioned in a diamond shape. Horizontal rhombic antennas are the most commonly used antennas for point-to-point HF naval communications. The main disadvantage of this antenna is that it requires a relatively large area.