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

Tue Oct 23 00:35:22 UTC 2012

Dale I guess a couple of comments to you and everyone. I am not an expert
on the chip. I downloaded what was available and thats not all that much.
So if someone has the experience to know whats actually correct and how to
turn this magical 20 cent chip into something useful, I am all ready to
hear the answer.

I do not believe that the system uses a varicap or VTO to tune things
instead I will speculate they drop cycles in the count chain. But thats
simply a guess. No matter what I simply could not get the system to put out
the 1s and 0s I was putting in. But spent only a few nights on it because
the reality is its only a part of the answer. The costas loop is the nice
piece. But ahead of that it needs a somewhat healthy signal to drive it so
there is more to the puzzle like agc and such.

To the easier part of your 2 questions.

The BPSK modulator was reasonable. It can be created a lot of ways but we
are talking 60Khz and that opens up things like opamps etc. But real simple.
I take a 60 khz sig generator, locked to a RB reference at 1 volt pp. Run
that to a xformer primary. These are radioshack class they work great at 60
Khz who would have thought. The secondary center tap is grounded and I
select plus or minus phase with a CD 4016 analog switch. Using a single
supply everything is biased at 1/2 VCC and then isolation caps for the
signals.
To switch correctly at the zero point I sample the plus of the secondary
with a LM339 comparator (only using 1 section) and feed that to a SXB micro
running at 40 Mhz. Detect the zero and switch if I want. The micro programs
in basic and screams along. So I can flip at any rate or create patterns as
easily as I can think them up. Its seriously dumb, simple, and stupid. But
it lets me run tests without waiting for wwvb. I do attenuate the output
signal to about 60 uv. Generally what I see on the east coast during the
day.
Regards
Paul
WB8TSL

On Mon, Oct 22, 2012 at 9:18 AM, Dale J. Robertson <dale at nap-us.com> wrote:

> Paul,
> I would also be interested in how you built your simulator.
> I'm considering building a simple one myself.
> I'll probably have mine just toggle the phase every 100 ms initially.
> Dale
>
> -----Original Message----- From: paul swed
> Sent: Sunday, October 21, 2012 11:08 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] WWVB New Modulation five cent demodulator /
> carrier regenerator ?
>
>
> 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
>> >>
>> >>
>> >> ______________________________****_________________
>> >> time-nuts mailing list -- time-nuts at febo.com
>> >> To unsubscribe, go to https://www.febo.com/cgi-bin/****<https://www.febo.com/cgi-bin/**>
>> >> mailman/listinfo/time-nuts<
>> https://www.febo.com/cgi-bin/**mailman/listinfo/time-nuts<https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts>
>> >
>> >> and follow the instructions there.
>> > ______________________________**_________________
>> > time-nuts mailing list -- time-nuts at febo.com
>> > To unsubscribe, go to
>> https://www.febo.com/cgi-bin/**mailman/listinfo/time-nuts<https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts>
>> > and follow the instructions there.
>>
>> ______________________________**_________________
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to
>> https://www.febo.com/cgi-bin/**mailman/listinfo/time-nuts<https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts>
>> and follow the instructions there.
>>
>>  ______________________________**_________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/**
> mailman/listinfo/time-nuts<https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts>
> and follow the instructions there.
>
> ______________________________**_________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/**
> mailman/listinfo/time-nuts<https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts>
> and follow the instructions there.
>