Hi,
Actually, even with some unknown fields, as you have the majority know
through prediction, much of the gain is being had that way.
The actual information rate of even GPS is very low.
Cheers,
Magnus
On 03/06/2017 08:26 AM, Bob Camp wrote:
Hi
One way to “cheat” at recovering a time signal is to demodulate it with
known information. Once you know the information from the first “frame”
of data (time, date, etc) you can predict what the information in the next
frame will be. Yes it does take a little work. If the signal is completely
defined
(no extra data about the weather forecast or something like that) you can
reduce your bandwidth significantly.
Bob
On Mar 5, 2017, at 11:42 PM, Iain Young <[email protected]> wrote:
On 05/03/17 20:23, paul swed wrote:
Gilles what signal is that at 162KHz. A European station? Nice thats its C
controlled.
That's TDF from France. Their equivalent of WWV/MSF/DCF. Used to carry
the AM Station France Inter as well, but that went when France turned
off all LW, MW, and LORAN stations at the end of 2016.
The Time Signal is Phase Modulated (I have a gnuradio decoder which
works very well if anyone is interested)
See https://en.wikipedia.org/wiki/TDF_time_signal and
https://en.wikipedia.org/wiki/Allouis_longwave_transmitter
With no AM modulation, there are obvious benefits with regards to using
it as a frequency reference. Average phase and frequency deviation is
zero over 200msec (see link above for details)
Iain
PS, The signal is used by the French railways SNCF, the electricity
distributor ENEDIS, airports, hospitals according to the Allouis link
above
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