The program broadcasts a radio packet that contains the 5-byte string `Hello` over channel 20 (which has a center frequency of 2450 MHz). The `loopback` program running on the Dongle is listening to all packets sent over channel 20; every time it receives a new packet it reports its length and the Link Quality Indicator (LQI) metric of the transmission over the USB/serial interface. As the name implies the LQI metric indicates how good the connection between the sender and the receiver is.