Enigma ID ...

Name F11
Frequencies Many different frequencies spanning 4 to 20 MHz
Status Active
Voice N/A
Emission mode USB AFSK, 100 bd, 620 Hz, ACF=16/96
Location Poland
Activity pages

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Known counterpart stations E11, G11, S11, S11a, M03

Run by one of Polish intelligence agencies. Its active counterparts are E11 and S11a. Its defunct counterparts are G11, S11, and M03.


It is a continuous audio FSK system, using the configuration of 100 baud and the shift of 620 Hz. This mode carries 5-digit group messages with attached 4-digit schedule ID to them, using a custom protocol without any error correction mechanisms. Both non-traffic and traffic formats exist. For a detailed reverse-engineered specification of the protocol, see this page.


All F11 schedules are weekly, follow year-round UTC (no DST adjustments), and use three different frequencies depending on the month - one for November to February, one for May to August and one for the remaining months. For most of the time there is no traffic, and one random week of the month a message is sent that always consists of 30-38 groups (excluding "88888"). Those always have a repeat transmission in the same week.

Each F11 transmission is followed 5 minutes by a repeat of it on the same frequency. Normally 10 minutes after the repeat, an E11, S11a, or M03 transmission comes up, carrying the same message, always on a nearby frequency, normally up to 1 MHz away.

However, not every single analog schedule has a digital equivalent.

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