[time-nuts] WWVB teensy BPSK early experiments

[John C. Westmoreland, P.E.]

Hello Time Nuts,

I have a question -

Has anyone been successful getting WWVB to decode using the example for
DCF77 and making the changes for WWVB?

Chris has his own approach - it's interesting - but on my setup at least I
haven't been successful with it - maybe it's my antenna - not sure just yet.
Also - my screen eventually 'whites-out' after running that for a while -
meaning - the screen goes completely white and I don't know what's doing
that yet - I suppose it's a bug of some sort.

But, with the DCF77 approach - it appears to identify bits OK - with the
code having only minimal changes - so I'd like to go down that path.

Note - I have a fork here - but it's debug - and not sure it's worth
anything other than looking at some of the data that's being dumped.
https://github.com/jwestmoreland/Teensy-DCF77

For DC7FF - the AM is just 0.2ms (1) and 0.1ms (0) with no AM at the minute
marker, but WWVB is a little more complicated -
0.2ms (0), 0.5ms (1), and 0.8 ms (Marker) - 2 consecutive markers mark the
end of current minute/beginning of next minute.

The DCF77 code seems to take some advantage of the signal level/timing and
the dimensions of the TFT display for
displaying the signaling - at least that's what it appears to me right now
unless I'm looking at this wrong - I guess that isn't
a big deal until you try to deal with the marker timing for WWVB - of
course I could be looking at this wrong right now too.

Maybe trying something like the Goertzel algorithm like KE9NS has done in
his work with WWV is worth taking a look at too with
this setup.

73's,
John
AJ6BC





On Sun, Nov 1, 2020 at 10:50 AM Mike Feher <mfeher at eozinc.com> wrote:

> Too bad I am an old retired hardware engineer and know nothing about these
> new SW controlled devices. Have Fun - Regards - Mike
>
> Mike B. Feher, N4FS
> 89 Arnold Blvd.
> Howell NJ 07731
> 848-245-9115
>
> -----Original Message-----
> From: time-nuts <time-nuts-bounces at lists.febo.com> On Behalf Of paul swed
> Sent: Sunday, November 1, 2020 12:48 PM
> To: Discussion of precise time and frequency measurement <
> time-nuts at lists.febo.com>
> Subject: Re: [time-nuts] WWVB teensy BPSK early experiments
>
> John sent the link on the teensy wwvb AM receiver. It can easily be
> shifted to other frequencies. Using the work Frank dcf77 and then Chris
> wwvb did with the PJRC audio design tool gives quite a bit of insight to
> the work that was done.
> The system assumes a sample rate of 192Khz. That limits the receive range
> to about 98KHz.
> I have not been able to confirm the rate I am using is 192Khz and when the
> set command is used its not recognized. So somethings up.
> The design Chris has essentially is a microphone input with some 38 db of
> gain feeding a bandpass filter around 60 KHz to a multiplier (RF mixer)
> then a low pass filter. Chris and Franks design is much more than these few
> words with spectrum display, signal level, and AGC.
> So without any effort the frontend solution is sitting in the teensy that
> cuts out a bunch of typical wiring. Granted its not as tight as discrete
> components can be. But its a chunk of software code. No digi key orders for
> L & Cs... :-) The output of the chain is 600 Hz audio that does contain the
> phase changes.
>
> But the trick is creating the true I & Q channels. Not an issue to add a
> second multiplier and chain did that last night. But at someplace a 90
> degree phase change or delay needs to occur.
> Or as suggested a hilbert transform.
> Regards
> Paul
> WB8TSL
>
>
>
>
> _______________________________________________
> 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.
>