FM/TV interference into rate 1/2 FEC encoded SCPC/QPSK

This paper presents some results obtained in laboratory measurements of interference caused by FM television signals to encoded SCPC/QPSK carriers. Certain parameters, such as the TV energy dispersal excursion, the frequency spacing between wanted and interfering carriers, the SCPC bit rate, etc., were varied during the measurements in order to study their influence on the amount of interference suffered by the SCPC channel. Computer simulations were also carried out in order to analyze and interpret measurement results obtained in some cases. Conclusions are drawn on the use of a possible interference criterion when rate 1/2 convolutional encoding and soft decision Viterbi decoding is used in the SCPC system as well as on the expected improvement with frequency offset.