EDIT: How can one find location of a jammer? I'm interested in the process and equipment needed to find location of active jamming device in a geographic area. E.g. what police uses and how can an average person like me do the same.
There are relatively inexpensive Software Defined Radio devices to enable this sort of thing. See:
https://www.crowdsupply.com/krakenrf/krakensdr
Other related discussions here on HN:
If you wanted to do it cheaply and crudely, you at least need a portable spectrum analyzer that covers the frequency range you're investigating and a rubber ducky antenna that covers the frequency range you're investigating and then drive around watching for where the signal strength increases. (Make sure the antenna is outside the car since the metal of the body will interfere with reception of signals.)
Professional spectrum analyzers used for engineering are quite expensive (I'm told that Rigol's SAs are good for the price) but you might be able to get away with less expensive instruments like the RF Explorer or even an RTL-SDR and one of the software spectrum analyzer packages out there, assuming they cover the frequency range you're interested in. By definition, jamming needs to be powerful enough to drown out any competing signals so it should be obvious if jamming is occurring even to relatively low sensitivity instruments.