Analog hand-held radios, aka. walkie-talkies, are still a viable option to mobile phones in many situations. Their users are generally aware of the drawback that they transmit in the clear, without any encryption.

Some radio manufacturers offer privacy options like 'privacy channels' and voice scrambling to prevent eavesdropping. We'll take a look at how secure exactly some of these legacy techniques are, as well as some ways to use signal processing and visualisations to un-scramble frequency inversion, split-band inversion, and rolling-code scrambling.