XPB is a digital mode of the Russian 7 operator. It utilizes a custom 16-tone MFSK system.

All XPB schedules are twice weekly and consist of 6 identical transmissions 10 minutes apart. Each successive transmission is 1-2 MHz lower or higher in frequency. The frequencies are typically changed on a monthly basis.

History

The on air tests of what would later become XPB took place sporadically from late 2014 until mid 2018. The tests took form of transmissions made every 10 or 20 minutes for many hours in a row. The waveform has undergone multiple iterations during its development, as shown in the below recordings.

The first regular schedule of XPB appeared in November 2018, followed by the second in September 2019.