There's a fun toy I just got called 'TinySA' (tiny spectrum analyzer). For $60, plus an adapter + some wire (another $20 maybe), you can get a live battery pow

There's a fun toy I just got called 'TinySA' (tiny spectrum analyzer). For $60, plus an adapter + some wire (another $20 maybe), you can get a live battery powered little receiver that shows noise across the whole spectrum from less than 1mhz through 350mhz. A really basic loop of wire is a directional antenna, so you can narrow down exactly what is causing issues too. I'm doing it to find noise issues for my ham radio setup, but it can be generally fun. Not quite an SDR, but to find noise sources it's pretty amazing for so cheap.