Hello I'm now studying transmission line theory. I got to know how impedance matching between characteristic impedance of transmission line and electrical load is important to achieve maximum power transfer and minimize power reflection which causes danger for the system. But the textbook doesn't tell one thing: Impedance matching between source impedance and the line impedance. Is this also important as much as impedance matching between the line and the load? And also I had some experiment to see impedance matching effect by myself. Our delay generator (DG535, Standford Research) generates TTL signal and output channel impedance can vary between 50 Ohm and High Z. Our lab only has BNC cable of 50 ohm of its characteristic impedance. In experiment, I connected such BNC cable to DG535 and Oscilloscope (OSC). DG535 is set to get source impedance of High Z. When I set OSC impedance of 50 Ohm, I remembered signal was distorted or reduced in amplitude while High Z set gave clean shot. This is what I really don't understand. The cable and OSC impedance is not matched (50 Ohm, High Z) and why I can get clean signal? It seems contradiction of what I've learned in textbook! And even source impedance and the cable is also not matched (High Z, 50 Ohm). It is like I have double unmatched points. Could you tell me how signal can be clean in this case?