What you see with nearfield probes ...

Here's a helpful article on using nearfield probes with a spectrum analyzer to fix EMI problems on PCBs.

In EMI/EMC troubleshooting, near field probes (NFPs) are great tools. But do you understand what you really see at the screen of your instrument with a magnetic near field probe?

EMI/EMC problems (radiated and conducted emissions) are usually related with current in circuits: high frequency currents (i.e. high di/dt currents) are responsible of radiation from PCBs, cables, slots and apertures, ground noise, crosstalk, etc.   A magnetic field probe (loop) is a great help in identifying where the culprit signal is being created (ringing, parasitic oscillations, harmonics, etc.). 
And it is common to use near field probes with spectrum analyzers. In this way, you see the spectrum of the signals close to the probe and it is easy to measure the frequencies involved in the test.

Read on here:

 http://snip.ly/je6yt9