The RTL-SDR devices (V3 and V4) have gained popularity among radio amateurs because of their very low cost and rich features. A basic system may consist of a USB based RTL-SDR device (dongle) with a suitable antenna, a Raspberry?Pi?5 computer, a USB based external audio input-output adapter, and software installed on the Raspberry?Pi?5 computer. With such a modest setup, it is possible to receive signals from around 24?MHz to over 1.7?GHz.