[time-nuts] WWVB PM Time Questions

[rcbuck at atcelectronics.com]

Paul,
"The new de-psk-r I built has no raw wwvb outputs." What do you mean by
raw?

I have been thinking about how the phase shift could be detected in
software instead of hardware. Could something like this maybe work:

If a micro is able to detect the zero crossing of a sine wave it should
be able to determine if the phase shifts. When a new second starts
(which is easy to determine), delay for 300 msec and then watch for the
next zero crossing. Store the time at that point. Then wait 1000 msec
which would put you at the same point in the next second. Wait for the
next zero crossing and determine the time between that crossing and the
first crossing. You can compute the phase difference based on the time
difference. If the phase difference is between 100 degrees and 180
degrees, you know a phase shift has taken place. The reason for using
100 as the low number is in case the zero crossing on one sine wave was
at the leading edge and it was on the trailing edge of the other one.

You would want to use the output of the PLL to perform those operations
since it is local and not subject to ionospheric interference or delays.
A 100 MHz STM32 should be able to easily handle the calculations in a
couple of microseconds.


Ray,
AB7HE

-------- Original Message --------
Subject: Re: [time-nuts] WWVB PM Time Questions
From: paul swed <paulswedb at gmail.com>
Date: Wed, July 29, 2020 8:07 pm
To: Discussion of precise time and frequency measurement
<time-nuts at lists.febo.com>

John
Thanks for jumping in and sharing what you have done. OK just maybe I
can
get the receiver online with a TCXO class oscillator. Or just go buy the
digikey unit and follow what you have done. What the heck all of the
rest
of the receiver is the same.
That leaves just one problem. A terrible one to have. The new de-psk-r I
built has no raw wwvb outputs. I debated about adding one. Woulda
shoulda.
Appreciate you jumping in.
Regards
Paul
WB8TSL

On Wed, Jul 29, 2020 at 10:00 PM John Magliacane via time-nuts <
time-nuts at lists.febo.com> wrote:

> Greetings to the group!
>
> I've been an FMTer for years, and an occasional "lurker" here, but as I
> find my ears occasionally "whistling" from time to time, I thought it was
> time to join in. :-)
>
> > On Jul 22, 2020, at 3:51 PM, paul swed <paulswedb at gmail.com> wrote:
> >
> > Ray watch out for my comment on the KD2BD solution. That oscillator isn't
> > available and I have not been able to map something else into it. Tried
> > several good grade Oven oscillators. Just be aware of that issue.
> > Would need to do more tinkering and simply don't have that time right
> now.
> > Also it would be great if the oscillator was something that could be
> > obtained at a reasonable cost. I do not believe at all it has to be a
> > OCXO as the older true time and spectracoms were not and they locked
> solid.
> > So its a case of getting the control voltages right.
>
> As Paul correctly stated, the Bomar VCTCXO used in my WWVB Frequency
> Standard is no longer available, at least in single quantities.
> Fortunately, there are MUCH better alternatives available, but they require
> a little "finagling". Hopefully, this information will help.
>
> I have successfully used a Taitien model TTEAMCSANF-10.000000 High
> Precision VCTCXO in my frequency standard with excellent results. This
> oscillator operates on 3.3 volts, and produces about a 1 volt p-p clipped
> sinewave output. It has a +/- 5 ppm pulling range, and is controlled by a
> positive slope tuning voltage between 0.5 and 2.5 volts.
>
> I've used two of these oscillators so far (in different projects), and
> both seem to tune exactly to 10 MHz with a tuning voltage close to 1.551
> volts. However, YMMV. Use these numbers as a guide if your oscillator
> should have different specs.
>
> The attached schematic shows the original circuit at the top with the
> modified circuit at the bottom. A 3.3 volt LDO powers the oscillator, and a
> simple MFP-102 JFET amplifies the output to drive the subsequent 5-volt
> CMOS logic.
>
> The original oscillator was temperature sensitive, and took several
> minutes to warm up and settle down. I often had to manually tune the
> oscillator on power-up using the front panel tuning control to get it in
> the ballpark where it would eventually lock to WWVB.
>
> Now when I turn it on, the new oscillator locks to WWVB in about 30
> seconds, and just stays there. :-)
>
> Digikey carries it for $13.81.
>
>
> 73.000 de John, KD2BD_______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
_______________________________________________
time-nuts mailing list -- time-nuts at lists.febo.com
To unsubscribe, go to
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.