|Emission mode||USB; 62.5Bd DBPSK ACF=9728ms, 62.5Bd DQPSK ACF=4864ms|
|Known counterpart stations||E11, G11, S11, S11a, M03, F11, F03|
P03a and P03b are one-way digital modes that belong to the Polish 11 family. They were introduced circa early 2014, as standalone successors of the F11 + analog voice/Morse combo schedules. Currently, all new digital schedules of this family use a newer evolution of P03, F03, although the P03 schedules are still maintained.
Both modes utilize cosine-filtered PSK modulation, forward error correction, and data scrambling. They have a sound evocative of a wobbly carrier tone, very easy to confuse with the amateur radio PSK** modes. The broadcasts are made in USB. Each variant refers to a different modem configuration:
P03a: 62.5Bd DBPSK, centered at +1000 Hz
P03b: 62.5Bd DQPSK, centered at +1000 Hz
Each of the two variants has minor protocol differences other than the modulation.
Their schedules send twice a week, follow year-round UTC (no DST adjustments), and use one of three different frequencies depending on the month - one from November to February, one from May to August, and one for the remaining months. Each schedule always repeats 5 minutes after the first broadcast begins. On most schedules, each weekday carries a different message, which is repeated throughout the month (re-scrambled every week), and replaced on the first week of the next month.