[time-nuts] WWVB Measurements using DSP recovery

[Shawn Tayler]

If I could suggest a shorter and perhaps simpler solution.  Rather than reinventing the wheel, simply insert each value as read into a SQL database engine,  there are numerous free ones available, i.e. MySQL or Postgresql.  You could include a timestamp either with your code or the system can do it automatically for you.  To get your result a simple query against the table:

Select count(*), value from [table] group by value order by count desc limit 1;

A simple shell script up to something graphical could be used, the KISS principle would yield the best results I'd suggest.

It could provide your result Every few milliseconds with a properly built system and indexing of the table.



Sent from my iPhone

On Mar 29, 2011, at 6:57, paul swed <paulswedb at gmail.com> wrote:

> Now you see I like these up to date solutions with cheap components. I
> recently home brewed "YAGPSDO"  yet another GPSDO, just to see how its done.
> When I look at things like a frontend  and maybe a mixer thats easy stuff.
> Even adding a nice A/D converter etc is easy if you can solder the darn
> things.
> What gets tricky is indeed the programming of the processor. I would have to
> say on the GPSDO its really not much more then a single loop pid with just a
> drop of smarts.
> So back to this.
> I have read the high level comments. But can we get deeper detail. Can it be
> done lets say in basic language etc. The comment I read that struck a cord
> was that all you did was sample and put the information in roughly 1000
> bins. Then I assume look for the bin with the most counts and called that
> center frequency. Perhaps plotting that number out.
> Is that really it??? Sure various filtering could also be done.
> But if the above scenario were correct for me at least it gets interesting
> and do-able.
> By the way for definition my interest is indeed an alternate comparison
> method to GPS. Kind of a second reference since we lost loran.
> 
> Having just wrapped up my project with VE2ZAZ for the HP3586 DSS its time to
> move on to the tracor 599 and wwvb.
> Regards
> Paul
> 
> On Tue, Mar 29, 2011 at 2:54 AM, Poul-Henning Kamp <phk at phk.freebsd.dk>wrote:
> 
>> In message <4D9129D8.4060609 at comcast.net>, Greg Broburg writes:
>> 
>>> Can you show a circuit of what you have done?
>> 
>> Basically I have a 20MSPS PCI card in a PC and do it all in
>> software.
>> 
>> I did use similar principles to implement a LORAN-C receiver
>> in a aduc7216 (http://phk.freebsd.dk/AducLoran/) but that is
>> passe for US people now.
>> 
>>> Would you recommend the 7200 again or something
>>> else that is better suited?
>> 
>> The most user friendly way to do it, would be to have a small FPGA
>> which takes data from the ADC and averages it into a small piece
>> of multiplext or dual port RAM, and a microcontroller (ARM ?) on
>> the other port, doing all the high level stuff.
>> 
>> That way there is no real-time component to deal with in the
>> programming, and anybody should be able to play with the code.
>> 
>> The alternative is to use a DSP to read the ADC, do the
>> averaging and perform the high level functions.  That would
>> be a lot harder to program for most people.
>> 
>> The ADC could be 16 bits, and run directly from a house standard
>> of 5 or 10 MHz (looks like that would cost $4 from analog.com, isn't
>> this future amazing ?)
>> 
>> Add a high resolution DAC for steering OCXO's and a serial port
>> or USB interface and we're done...
>> 
>> --
>> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
>> phk at FreeBSD.ORG         | TCP/IP since RFC 956
>> FreeBSD committer       | BSD since 4.3-tahoe
>> Never attribute to malice what can adequately be explained by incompetence.
>> 
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