[time-nuts] WWVB New Modulation five cent demodulator / carrier regenerator ?

Dale J. Robertson dale at nap-us.com
Sun Oct 21 23:20:57 EDT 2012


Paul,
Did you move the frequency up by driving it with a function generator or by using a 4.56 or 9.12 MHz crystal? I'm thinking that maybe the quadrature phase lock is accomplished by an internal varacter or some other mechanism for 'pulling' the on-chip oscillator. That wouldn't work if you were  injecting the clock
Dale

Sent from my iPhone

On Oct 21, 2012, at 11:08 PM, paul swed <paulswedb at gmail.com> wrote:

> Jameco had them on sale for 20 cents each so I purchased some.
> Moved the clock up frequency for 60 Khz and injected the 60Khz BPSK. (I
> built a simulator) It did not track and in general produced noise. I
> understand you can use 2 frequencies to drive it and I tried both from
> synth gens.
> I was looking at the RDS decoders and the data seemed to be differential.
> Set it aside at that point. I am curious as to why it did not work. Like
> everyone here would be great if it worked....
> Regards
> Paul
> WB8TSL
> 
> On Sun, Oct 21, 2012 at 10:55 PM, Dale J. Robertson <dale at nap-us.com> wrote:
> 
>> Paul,
>> I'm trying to understand your reference to 'differential BPSK'  all the
>> RDS references I've looked at indicate a 180 degree phase shift just like
>> WWVB. I'm thinking that differential and antipodal are just different words
>> for the same thing
>> Regards,
>> Dale
>> 
>> Sent from my iPhone
>> 
>> On Oct 21, 2012, at 10:03 PM, paul swed <paulswedb at gmail.com> wrote:
>> 
>>> Because it use differential BPSK. I have a number of them and was trying
>>> it. There is a test pin that might make it useful.
>>> Regards
>>> Paul
>>> WB8TSL
>>> 
>>> On Sun, Oct 21, 2012 at 9:14 PM, Dale J. Robertson <dale at nap-us.com>
>> wrote:
>>> 
>>>> While looking for other stuff I came across the data sheet for the NXP
>>>> Semi SAA6579.
>>>> The chip is a purpose built demodulator for RDS (which utilises a 57 KHz
>>>> ABPSK subcarrier on FM broadcast that is) used for traffic, song info
>> etc.
>>>> This chip has an anti-aliasing front end low pass filter and an 8th
>> order
>>>> bandpass filter followed by a costas loop and provides a phase
>> synchronous
>>>> regenerated carrier. What's interesting is that the switched cap
>> bandpass
>>>> filter and the synchronous detector are both driven by clocks derived
>> from
>>>> a local crystal oscillator which is spec'd at 4.332 or 8.664 MHz (76 or
>> 152
>>>> X carrier chosen by a mode select pin) I'm thinking it should be
>> possible
>>>> to use a 4.56 or 9.12 MHz crystal or external clock to use this chip
>> as-is
>>>> on 60 KHz.
>>>> Have a look at the data sheet and tell me why I'm full of it.
>>>> Jameco is closing out these chips in DIP-16 at a nickel apiece,
>>>> $3.00/hundred.
>>>> 
>>>> Dale NV8U
>>>> 
>>>> 
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