Hi Paul -
If you can spend time on that:
1. Look for the different modulation spectrum between BPSK and RDS. The
phase modulation angle is different, the bits are manchester encoded or
such to get a hole on the carrier frequency (For the ARI carrier), the
baseband is DBPSK.
2. Carefully adjust the clock generator. Very sensitive to it!
3. The demodulator can lock on two different phase states. But the
difference is just where the clock transition is positioned in the
data-bit. In locked state this should be constant and can only change
the next time the chip switches von search to lock state (with a 50%
probability).
4. Yes, often such chips are interesting but poorly documented.
Sometimes it helps to look for similar devices like the SAA6588, TDA7330
, etc. Older datasheets often show more details.
5. I don't think you can use the chip with 1bit/sec. It is made for
1200bits/sec. I don't know if the internal digital part of the circuit
is fully static. But surely the capacitors of the filter are to small
for a 1200:1 dynamic range. Maybe I misunderstood this in your application.
Have fun -
Henry
paul swed schrieb:
> Henry
> Its been a while since that thread and I have not done anything with the
> chip. But to answer your questions.
> Really good signal to noise. The modulator is 6" from the saa6579. Its a
> home brew BPSK modulator and the transitions are programmable. But I am
> following wwvbs 1sec per bit. So the phase is quite stable for long
periods
> of time. Signal level is 1000uv but again that can be adjusted.
> Were is someone. My comment was someone on time-nuts suggested that
you had
> to use the clock and a flip flop to properly see the data. Thats what you
> are also saying.
> As to the wwvb modulation scheme I fully understand that. But I
actually do
> not know a lot about RDS and how it might be different from wwvbs
method of
> transmission.
> I believe there is plenty of information on RDS. I just don't have a
lot of
> time to figure it out.
> I will get back to the chip at some point it is really interesting
but very
> poorly documented unfortunately.
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