14.2 Single Access

With single access, a single modulated carrier occupies the whole of the available bandwidth of a transponder. Single-access operation is used on heavy-traffic routes and requires large earth station antennas such as the class A antenna shown in Fig. 8.7. As an example, Telesat Canada provides heavy route message facilities, with each transponder channel being capable of carrying 960 one-way voice circuits on an FDM/FM carrier, as illustrated in Fig. 14.1. The earth station employs a 30-m-diameter antenna and a parametric amplifier, which together provide a minimum [ G/ T] of 37.5 dB/K.

Figure 14.1: Heavy route message (frequency modulation single access). ( Courtesy of Telesat Canada, 1983.)