Abstract: There is provided an electronic amplification apparatus (40) comprising a travelling wave tube amplifier (20) and a limiter (10), wherein the configuration of the amplifier (20) is optimised whilst maintaining signal linearity for operation with improved DC power efficiency at an operating point below saturation, and the limiter (10) is arranged to prevent the output power of the amplifier from going beyond a predetermined limit. This can prevent possible damage. There is also provided a multiport amplifier system (50) containing the electronic amplification apparatus (40), and a multi-feed, multi-amplifier phased array type antenna system (130) containing the electronic amplification apparatus (40), and a satellite communications system comprising the electronic amplification apparatus (40) or the multiport amplifier system (50) or the multi-feed, multi-amplifier phased array type antenna system (130).

Abstract: There is provided an electronic amplification apparatus (40) comprising a travelling wave tube amplifier (20) and a limiter (10), wherein the configuration of the amplifier (20) is optimised whilst maintaining signal linearity for operation with improved DC power efficiency at an operating point below saturation, and the limiter (10) is arranged to prevent the output power of the amplifier from going beyond a predetermined limit. This can prevent possible damage. There is also provided a multiport amplifier system (50) containing the electronic amplification apparatus (40), and a multi-feed, multi-amplifier phased array type antenna system (130) containing the electronic amplification apparatus (40), and a satellite communications system comprising the electronic amplification apparatus (40) or the multiport amplifier system (50) or the multi-feed, multi-amplifier phased array type antenna system (130).

Abstract: A process or the liquid phase carbonylation of methanol or a reactive derivative thereof comprises contacting carbon monoxide with a liquid reaction composition comprising methanol or a reactive derivative thereof, a halogen promoter and a rhodium catalyst system comprising a rhodium component and a bidentate phosphorus-sulphur ligand, the ligand comprising a phosphorus dative center linked to a sulphur dative or anionic center by a substantially unreactive backbone structure comprising two connecting carbon atoms or a connecting carbon and a connecting phosphorus atom. Novel rhodium ligand complexes of formula [Rh(CO)L].sub.m and Rh(CO)LY] wherein Y is a halogen, m is a number less than 10 and L is ##STR1## wherein the R groups are independently selected from C.sub.1 to C.sub.20 alkyl, cycloalkyl, aryl, substituted aryl and optionally substituted aralkyl; the R.sup.5 groups are selected from hydrogen, C.sub.1 to C.sub.