I mostly fiddle with software-defined radios, Linux, computers and digital electronics when I am not diving. Here is an enclosed R820T Usb-dongle with a 433 MHz quarter-wave ground plane antenna with almost straightish elements. The dongle picks up all kinds of noise because of the antenna cables passing straight above the oscillator and the tuner-chip. Oh well. We learn something new every day.
Why 433 MHz? I want to see when the neighbour opens his car and when my father turns on the RF-controlled devices in the house. Now you know. Don't tell him.