The relationships and measurements of cross-modulation and intennodulation on combined signal working C.C.I.R. system a v.h.f. band III relay systems

In order to extend v.h.f. coverage in Great Britain to areas of relatively poor reception, the Independent Television Authority has recently commissioned a number of hybrid solid-state/valved combined signal working relay stations. Whilst this has led to a high level of performance and reliability, the use of combined signal working has introduced problems peculiar to this system in so far as the measurement of linearity is concerned. The paper describes a typical relay system and the methods of expressing the linearity requirements in terms of intermodulation and cross modulation are defined, together with the empirical relationship between cross-modulation degradation and the standard subjective severity scale.