Although much classical HF and mobile equipment is still in use by many amateurs, the use of computers and digital techniques has now become very popular among amateur radio operators. Nowadays, anyone can purchase a Raspberry Pi computer and run almost all amateur radio software on the 'RPi', which is slightly bigger than the size of a credit card. The RTL-SDR devices have become very popular among hams because of their very low cost and rich features. A basic system may consist of a USB-based ...