Radio nerd here. (73 y'all)
I've seen pictures of people getting arrested and one thing I've noticed is that every now and again I'll see an FRS/GMRS radio with some of these rioters.
What does that mean? Well, it means they're organized. And you can be too.
As a radio operator, when we do events and such a common thing to do is to set up a "net control" or central command or some sort of base station. This station will have high power and an effective antenna. People can then meander around with an HT (handheld radio) and communicate back to the base.
This is effective in that two HT's, which are lower power and don't have a nice antenna profile, can communicate via the base station (otherwise known as a repeater).
This can work in a couple of different ways. In repeater mode, the HT's can all communicate with the higher power repeater and it rebroadcasts and everybody hears it. Or there might be a net control operator, the HT's communicate with net control (a person) and net control responds with advice or orders or some sort of information they wouldn't otherwise have.
This radio right here is one that is inexpensive and that I've seen used by people getting arrested. https://www.amazon.com/dp/B07BXCF85T/
Knowing radio technology, I can take an educated guess and say they're using GMRS. Here's why, a nice chart that shows the overlap between FRS and GMRS frequencies: https://wiki.radioreference.com/index.php/FRS/GMRS_combined_channel_chart
You'll notice peak FRS power is 2w while GMRS peak power is 50w. If they're following legal operating power, which a lot of radios require in hardware, then that means they're operating between the frequencies of 462.5500 - 467.7250.
What does this mean and what can you do?
Well you can get a GMRS radio and antenna and listen and record. This is evidence if they're coordinating criminal activity and could help in a RICO case.
So what to do... Keep in mind this is a "line of site" radio technology, so everything's within a mile or so.
Option 1: You can spend $20 on the same radio I posted (or any GMRS radio) and set it to scan between the above frequencies. You're free to roam around.
Option 2: You can get a GMRS radio (even the HT) and use a vehicle mounted antenna. This will use the vehicle as a ground plane and have much better reception, around 3.5dBi. Example: https://www.amazon.com/dp/B00NWYVM94
Option 3: You can get a base station antenna and radio, this will have the most gain (up to 6.5dBi) with this antenna, but you're not going to be mobile. Example: https://www.amazon.com/dp/B0784FQ9VB
They're talking to each other and coordinating right under your nose, this is how you go about listening in. Record any crimes. Fuck it, give them false orders too. Don't let them own this technology, we can use it too.
Fellow radio nerd here. Not a HAM, but an Electrical Engi with a focus in Applied Emag/Comms. Theoretically, if we had enough base stations with power measurements, and could get power readings, it should be fairly trivial to triangulate a rough position of where the broadcasts are coming from. Granted, multipath scatter in a city will make any kind of pinpoint situation difficult, however, but given that we have a rough idea of the actual transmit power, mixed with someone on the ground, it should be possible for some kind of combination of techie power and good ole fashioned on the ground surveillance to get an idea of where things are coming from.
Additionally, for folks on the ground wanting to do near-range signal exploration, the low-cost RF Explorer spectrum analyzer paired with a directional antenna could get you an idea. Note, these are uncalibrated devices, so you're not going to be able to get much use from the triangulation perspective, but you will be able to likely perform direction finding (assuming you have a directional antenna).
Oh a get 2-3 people with box or yagi antennas and you can triangulate rather easily. Once you get close attenuate the noise and you can walk right up to the base station. We do fox hunts with much lower power transmitted!
For sure, but it also depends pretty heavily on the terrain. If you've got open line of sight, sure, but if you're in the shadow of a tall metal or brick building, you're a lot less likely to see a signal to start with. It's the major multipath problem if they're trying to Rx at the street level in urban environments. You can in some cases point an antenna in a direction and if there's a large enough building in the way, you might miss it, especially if there's less attenuated diffusion through a semi-adjacent path, say an adjacent street..
Never done the foxhunt thing though it does sound like fun. I'm pretty sure RF explorer makes a signal generator too, if you're ever looking for a tiny inconspicuous Tx for a foxhunt.