by Maurizio @ dev.emcelettronica.com:
Using simple wires to measure signals with the oscilloscope would result in unreadable plots on the scope, the main reason being the noise coupled onto the “probe” itself. The first line of defense against that would be to use a coaxial cable as a probe, which would prevent external noise coupling.
An unwanted deterioration of the measured signal is due to the capacitive loading that such a piece of cable adds to the signal. An equivalent schematic of an IC to IC signal is illustrated in figure 1.
Compensation of Oscilloscope Probes – [Link]