Here's a naive question: When two countries have specified (as in NET 4) different reference impedances for measuring return loss (in a modem), how likely is it that the network equipment in one country is actually differerent from the equipment in the other country?
Another way of asking might be this: Could it be true that network line cards are really 600 ohms resistive worldwide, and that the complex reference impedance specified was chosen to approximate the impedance presented by the combination of the network equipment and the real-world loop? (With the intent that equipment designed to provide a complex source impedance would peform better than equipment designed for 600 ohms) Don RCIC - http://www.rcic.com Regulatory Compliance Information Center
