[time-nuts] Allouis 162 kHz time signal [was: Re: new WWVB BPSK dev board]

[Pieter-Tjerk de Boer]

On Wed, Dec 05, 2018 at 08:23:59PM +0000, Poul-Henning Kamp wrote:
> --------
> In message <D1E866D9-3A6E-472F-A780-61CB03DE3FCB at club-internet.fr>, Club-Intern
> et Clemgill writes:
> 
> >- One bit only is coded per second in each minute =>  59 bits available because...
> >- 59th second is silent (no phase modulation)
> 
> I belive this is wrong.
> 
> The timecode (substantially the same as DCF77) occupies only one
> bit (the first) in each second, but more bits are encoded each
> second after the first one, I belive for some kind of "telecontrol"
> scheme.

Yes, that's correct.
In the remaining part in each second, more bits are transmitted, using
a more complex three-level modulation scheme, with a data packet format
defined for it.
However, it has never been used for actual user data (so I was told by
someone from CFHM, the organisation behind this time signal).

So effectively it is only transmitting idle frames, which boils down to a
1-minute-long ever repeating pseudo-random sequence.
Being completely predictable, this sequence could be used to improve timing
receiver accuracy.

The Allouis signal can be seen live here: http://websdr.ewi.utwente.nl:8901/tdf/

And here's another, perhaps even more nutty, example of decoding the signal:
http://www.pa3fwm.nl/signals/clock-lille-flandres/

Regards,
  Pieter-Tjerk, PA3FWM