[time-nuts] WWVB teensy BPSK early experiments

Tue Nov 3 14:49:35 UTC 2020

John
Yes I have used Chris's code to decode the wwvb AM timecode. I am in Boston
so just about as far away as you can get. Though maybe Florida is further.
But Boston is in more of a null from wwvb.
Granted the antenna is a tuned 10' X 10' 800 ft of wire loop and preamp
mentioned numerous times on time-nuts. It reliably during the day delivers
100 uv at the end of the coax.
I found the teensy wwvb sdr really worked best during the day. With respect
to power for the antenna its just a power inserter I built, 8 Mh choke, 100
ohm resistor, .47 uf coupling cap to the teensy. No magic at all.
One very serious issue with the teensy is that the audio module must be
directly stacked on to the cpu. I originally used 3" leeds those little
jumpers. It makes a mess of the clock signals.
Regards
Paul.

On Mon, Nov 2, 2020 at 10:55 PM John C. Westmoreland, P.E. <
john at westmorelandengineering.com> wrote:

> Paul,
>
> Have you successfully decoded WWVB with Chris's code?
>
> I haven't gotten that to work.
>
> I'm using the same antenna set up I've used that works with the multipsk
> Clock program to decode WWVB that will decode fairly reliably as long as
> atmospheric conditions are favorable.
>
> Note, if using the Arduino IDE and you're connected to a PC; it will
> sometimes set the clock on the TFT to the PC's clock; I'm mentioning that
> since some that try this could think their set up is synced to WWVB when it
> actually grabbed time from the PC.  Maybe the loader from Teensy does that;
> I haven't looked close enough yet to know for sure what's setting that.
>
> Glad you're making progress with your approach.
>
> 73's,
> John
> AJ6BC
>
>
> On Mon, Nov 2, 2020, 18:20 paul swed <paulswedb at gmail.com> wrote:
>
> > John thats exactly what Chris did. Its the teensywwvb.ino. It decodes the
> > AM timecode just as the DCF code does. In fact Chris's code is derived
> from
> > the DCF code with the changes you are asking about and it works. Download
> > his solution and read the comments throughout. The original DCF comments
> > are in it also.
> >
> > Its the starting point for the tinkering I am doing towards a BPSK SDR.
> > Thats a big leap for me.
> > What the code gives you is the frontend gain, followed by a bandpass
> > filter. Multiplier that mixes the LO and incoming signal to a lowpass
> > filter. Then on to AM detection and AGC.
> >
> > If you don't care to install the arduino IDE with teensy extension just
> use
> > notepad ++ to look at the code. Pretty exciting.
> >
> > Regards
> > Paul
> > WB8TSL
> >
> > On Mon, Nov 2, 2020 at 8:24 PM John C. Westmoreland, P.E. <
> > john at westmorelandengineering.com> wrote:
> >
> > > 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
> > > >
> > > >
> > > >
> > > >
> > > > _______________________________________________
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