Minimum Signal to Interference Ratio Required for Broadcasting

Abstract

In order to determine the level of maximum interference at which a satisfactory broadcasting service is possible, a large number of listening tests were conducted. The study has been confined to the determination of protection required for a speech modulated broadcast signal against interference from speech and music and also against CW Morse. The experimental set-up is described in detail in the paper. More than 750 recordings were made and about 12,000 individual opinions collected. The analysis of the listener's opinion indicates that minimum protection of about 33 db is required for zero-beat operation and 52–54 db at frequency separation of 2–3 kc./s. Beyond 3 kc./s. the protection becomes gradually lower and after 5 kc./s. it drops down sharply. Other factors influencing the desired protection have been discussed.