Viewing a Network Signal; Physical level

I have looked around, but I can’t find out what exactly is on a 10baseT or coax wire for a network. What frequency is it? FM,AM? Is the signal pulsed on a wire, CW? Does it ride a DC offset? If I were to draw on a blackboard, a signal with data on it, for CAT 5 ethernet, or coaxial wire, what would it look like? For any that have viewed the wire, do you find it better to see with an oscilloscope, or a spectrum analyzer? (I only have enough budget for 1!)