The most effective device I have for tracking MF noise is a vintage transistor AM radio.  These old radios are available for a dollar or two at garage sales, and for a few tens of dollars on eBay.  Here's a link to photos of my favorite noise-hunting radio:  a Motorola transistor radio from 1971.

It is completely portable and has an internal bidirectional loop antenna.  You can couple the radio close to possible noise sources to hear the sound of the interference and pinpoint the source.  And the nulls off the ends of the radio are quite sharp so you can take bearings and triangulate more distant sources. 

I tune the radio to an unused broadcast channel and listen to the background noise.  I go toward the bottom of the AM band (550 kHz) when I am interested in the noise bothering 630m and the other services below the AM band, and tune toward the high end of the AM band when I am interested in 160m or HF noise sources.  Usually very helpful, and often the noise I am seeking is spewing all across the band so tuning is not critical (other than to be tuned between active broadcast stations on an open frequency).

The horizontally-oriented design radios like this one often have a longer ferrite loop antenna inside which makes for higher performance, deeper nulls, etc.

I describe using this radio to track noise in my presentation: