The accurate measurement of high attenuation at radio frequencies

Techniques are described which allow the traceable measurement, at low uncertainty levels, of changes in attenuation value in excess of 140 dB at frequencies from 0.5 MHz to 100 MHz. The coherent nature of the dual channel techniques employed allows the changes in the path length through an attenuator, produced when its setting is changed, to be measured accurately even at high attenuation levels.<>