To the Moon!

摘要

You can go to any electronics store and buy a length of RG58 coaxial cable. The description written on the shelf reads "50 Ω cable." But what does this really mean? If you take an ohm meter to the cable, will it read 50 Ω? If you snipped off a three-foot length and touched one lead of the ohm meter to the center conductor and the other lead to the adjacent shield, what would the ohm meter read? If the ohm meter doesn't read 50 Ω, what does it mean to have a 50 Ω cable or a 50 Ω trace on a circuit board?