Transmission Line Demonstration
Here I demonstrate a simple “model” of a transmission line, which consists of a string of inductors and capacitors distributed in a linear fashion. I placed LEDs and their current-limiting resistors across each capacitor to act as simple “visual voltmeters” to show the peaks and nodes of the standing waves of voltage in the line. The line is fed by a DDS function generator which is set to sweep across frequencies from about 10 kHz to 1 MHz during several seconds. As the frequency changes, the positions of the nodes and peaks of the standing waves travel along the line, and this is visualized by the fading and brightening of the LEDs.