Portable software defined radio.
https://www.amazon.com/Software-1MHz-6GHz-Frequency-Bandwidth-Adapters/dp/B0BKH7Z2NJ
https://www.amazon.com/RTL-SDR-Blog-RTL2832U-Software-Defined/dp/B0CD7558GT
https://www.onesdr.com/best-sdr-for-raspberry-pi/
A lot more online on how to build and use.
@corlin
Way over my pay grade. But others?