Simple Transmission-Line Experiments

38 SIMPLE TRANSMISSION-LINE EXPERIMENTS by Roy C. Whitehead, C.Eng., MIEE This article describes some simple transmission-line experiments that were developed for the UNCLE scheme. Under this scheme, which was initiated by the IEE, but later joined by other learned societies, members (usually retired) volunteer to go to schools to help teachers to bridge the gaps that exist between the academic world and the world of practical engineering. The material used in the experi- ments consisted of: • a known length of coaxial cable of which both ends were accessible; • a twin-beam oscilloscope; • an HF generator with 75 SI output; • three 100 fl non-inductive potentiometers; • an ohmmeter. Measurement of velocity ratio The equipment should be con- nected as shown in Fig. 1. Set P1 to its maximum resistance value and the two Y sensitivity con trols of the CRO to produce equal values of Y sensitivity. Set the signal generator to its minimum available frequency and note the small ...