[time-nuts] C-Max Receiver Experiment

Justin Pinnix justin at fuzzythinking.com
Mon Oct 31 12:48:15 EDT 2011

On Mon, Oct 31, 2011 at 1:54 AM, David J Taylor <
david-taylor at blueyonder.co.uk> wrote:

> Nuts,
>> I recently picked up a C-Max evaluation kit from SparkFun to see if this
>> $10 board could be used as a precision timing source.  The short answer is
>> no.  The long answer is available at:
>> http://www.fuzzythinking.com/?**page_id=29<http://www.fuzzythinking.com/?page_id=29>.
>> It was a fun experiment and a great excuse to play with test equipment :-)
>> Thanks,
>> -JP
> Thanks for posting that, Justin, it was most interesting, and the
> reference to Brooke Clarke's page, which I did not know.
> It would be interesting to know what the analogue signal looks like, as
> many pieces of electrical and electronic equipment can radiate
> significantly on those frequencies.  I expect you optimised the signal,
> though, as you've mentioned it.
> Are you sure the images are all correct?  To me, your Fig 2 and Fig 3
> images look identical, as do Fig 6 and Fig 7.
> "Precision" - well, that depends, doesn't it?  Perhaps more precise than a
> very poor Internet connection?  Better than no Internet connection at all!
> Certainly not GPS level.
> Cheers,
> David

Hi David,
Thanks for pointing out the problem with the figures in my webpage.  I have
fixed it.  I'm going to attempt to capture the analog signal by probing the
QOut pin.

Good point about "precision" - it's all relative.  This is an extension of
a previous project of mine - a clock I built around an LPro.  Setting it to
the Thunderbolt is a bit of a pain and I was hoping to build in the C-Max
to make it more "fire and forget".  I was hoping for a time signal within
several microseconds of UTC without the need of an outdoor antenna.  Like
most of my projects, the journey is more interesting than the destination,
so even if I don't accomplish that goal I'm still having fun.  Embedding a
consumer GPS is probably the more practical solution.


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