120-Mbit/s QPSK signal transmission tests via Intelsat V and Andover II link

An experimental investigation has been carried out to examine the performance of the 120-Mbit/s QPSK channel using a 72-MHz-bandwidth transponder of the Atlantic basin spare Intelsat V satellite (channel 5-6) and Andover II antenna link. The tests included a systematic equalization of the overall link and bit error rate optimization by trial and error using an adjustable transversal equalizer to 'fine tune' the link response. Channel sensitivity was evaluated by perturbing the up- and the down-link equalization. Interference analysis was performed by injecting a CW and an 1872-channel FDM/FM interferer in the up- and down-links, first individually and then simultaneously. Cycle skipping phenomena were observed under different channel conditions. The latest test data for 120-Mbit/s QPSK transmission through a 77-MHz transponder (channel 1-2) are also included.