[time-nuts] Alternative WWVB Spectracom solution

[Chris Albertson]

The software already exists to do this.  It is included with the standard
NTP source code in a directory called (from memory) "test".   It was
designed to test the time code clock driver.

You are right it is not complex, you can read the code and see how it was
done.


On Fri, Jun 14, 2013 at 6:45 PM, Tom Van Baak <tvb at leapsecond.com> wrote:

> Since the topic of WWVB came up again, here's another idea.
>
> A number of people still want to use (hp, or Tracor, or) Spectracom WWVB
> receivers as frequency standards or to maintain NIST traceability. As has
> been discussed on the list, these receivers no longer work now that the
> enhanced WWVB format is in effect 24/7. Paul Swed's Costas loop project is
> a nice hardware solution.
>
> I'm wondering if anyone wants to help on a mostly software solution.
> Here's the idea -- if you already know the time of day to a few
> milliseconds (from NTP, GPS, etc.) it should be simple to generate the live
> 1 baud data of the new PM code. The only hardware you need is an analog
> inverter/switch which then applies either a 0 or 180 degree shift to the
> antenna signal, based on the predicted state of the PM code for that second.
>
> In this case, every second, your local phase shifting neatly cancels the
> Ft Collins phase shifting. The PM bit prediction and edge timing don't have
> to be perfect, just close enough that the 60 kHz PLL stays happily locked.
>
> The advantage of this approach is that the existing WWVB phase tracking
> receiver can remain completely unmodified. You would simply insert the
> programmable inverter inline between the antenna and the receiver. For
> testing even a DPDT reed relay might do the job.
>
> It would be a good project for a RPi (running an NTP client) or an Arduino
> (using a cheap GPS NMEA+1PPS receiver). If you can spot holes in the design
> let me know. It seems too simple to be true.
>
> /tvb
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>



-- 

Chris Albertson
Redondo Beach, California