|Name||F03a, F03b, F03c|
|Emission mode||USB; Various BFSK and MFSK-4 modulations|
|Known counterpart stations||E11, G11, S11, S11a, M03, F11, P03|
The F03 designator refers to the BFSK and MFSK-4 modes. The following flavors have been spotted on the air so far:
F03a: BFSK, 100 Bd/200 Hz, Center +600 Hz, 448-bit blocks
F03b: BFSK, 200 Bd/400 Hz, Center +800 Hz, 448-bit blocks
F03c: BFSK, 400 Bd/960 Hz, Center +1120 Hz, 448-bit blocks
BFSK, 200 Bd/800 Hz, Center +800 Hz, 496-bit blocks
BFSK, 400 Bd/800 Hz, Center +1200 Hz, 496-bit blocks
MFSK-4, 100 Bd/200 Hz, Center +800 Hz, 448-bit blocks
MFSK-4, 200 Bd/400 Hz, Center +1000 Hz, 448-bit blocks
However, only F03a and F03b have multiple stable schedules that use those modes year round. The remaining modes' schedules tend to shuffle to different F03/P03 modes along with seasonal frequency changes.
All F03 schedules are twice weekly, follow year-round UTC (no DST adjustments), and use one of three different frequencies depending on the month - one from November to February, another from May to August, and yet another one for the remaining months. However, a very small minority of schedules follows this frequency usage pattern less strictly. There are always two identical broadcasts 5 minutes apart.
Each weekday typically carries a different message, which appears at the beginning of the month and is repeated throughout it; sometimes, both weekdays carry the same message, and sometimes a new message arrives in the middle of the month. Every week, the message is rescrambled, retaining only the headers and the length.