New timecode on Poland's 225 kHz signal

[phase plot] Since late 2023, Poland's longwave broadcast transmitter on 225 kHz additionally sends a time code as phase modulation. Many other longwave transmitters have been doing this for years, like the longwave broadcasters BBC on 198 kHz and France on 162 kHz (see also here and here), and dedicated transmitters MSF on 60 kHz and DCF77 on 77.5 kHz.

Still, it's surprising to see such a service start in 2023, when there are so may other ways to receive time information, and many longwave transmitters are being shut down. (However, looking in old recordings, it turns out that the phase modulation of this carrier with "Enea lighting control" messages has been going on for at least 8 years; only the time code is a recent addition.)

Documentation of the data format can be found at; only in Polish, but Google translate does a good job of translating it to English. Using this, I've implemented a simple decoder to go with my WebSDR at

While implementing this, I ran into a couple of unclarities, errors and omissions in the published specification ("version 1.0"), as documented here.
(Note: this list is not meant as criticism, but to help other potential implementers, and perhaps the authors of the specification to improve it.)


Some further remarks:

Comments are welcome, at