This section of IEC 835-1 deals with the measurement of basic characteristics common to terrestrial radio-relay systems and satellite earth stations. These basic characteristics apply to all of the frequency ranges employed in the radio systems, i.e: radio frequency; - intermediate frequency; - baseband (e.g. clock frequency of the digital baseband signal). The method of measurement for each parameter (e.g. return loss) is presented, wherever possible, as a single clause which is applicable to any of the above frequency ranges. Where exceptions occur, they will be given in the relevant clauses.