On Fri, 2006-12-08 at 21:06 +0000, Peter P wrote:
> I know a lot of projects use DCF77 in Europe. But I discovered that
> the French
> run a 2MW station on 162 kHz. This should be much easier to receive. I
> could
> never receive 77 kHz in a city (fairly far away from DCF77). Is anyone
> using
> this ? Reference:
> 
> http://en.wikipedia.org/wiki/T%C3%A9l%C3%A9_Distribution_Francaise
> 

There is a similar phase mod signal on the BBC Radio 4 signal on 198kHz.
I used a Crystal oscillator  at 12.288Mhz as the starting point.

12288kHz / 64 = 192kHz
198 - 192 = 6kHz
192 / 32 = 6kHz

Put the two 6kHz signals into a phase comparator and you get the
recovered phase shift data out as the DC component.  I fed this into an
ADC input on a PIC and decoded the data from there.  The eye diagram for
the data can be seen at the bottom left in this picture
http://www.btinternet.com/~Peter.Onion/PhaseData/p002107.jpg


Feed a low pass filtered version back to a varicap diode on the crystal
and you have a very accurate frequency source.

It was a bit of a lash up, but it did work.
http://www.btinternet.com/~Peter.Onion/PhaseData/p002127.jpg


I havn't worked out if a similar scheme can be used for 162kHz but it
may require a non-standard crystal frequency to start from. 


Peter

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist