[time-nuts] WWVB Dephaser Question

Tue Oct 13 19:50:04 UTC 2020

Hello Time Nuts,

Paul, I haven't gone over in fine detail of how the multipsk software is
working - so I'd like to answer with that caveat if that's OK.

I thought it was more interesting that I got anything working as far as
60kHz with my existing OpenHPSDR rig AND my default antenna.
The system wasn't really designed for that - and it worked.

I'll dig into some of the details and report back - since the time
information is all that is needed for clock synchronization - I think the
easiest method available is more than likely what was done.

It agrees with the GPS feed from Themis - so, that's a good check.  Also,
Themis is driving the reference clock for the HPSDR rig.

73's,
John
AJ6BC

On Tue, Oct 13, 2020 at 12:20 PM paul swed <paulswedb at gmail.com> wrote:

> John I looked at what you sent. I assume its decoding the am time signal is
> that correct?
>
> On Tue, Oct 13, 2020 at 1:19 PM Chris Howard <chris at elfpen.com> wrote:
>
> >
> > That's a fair assessment.  I'm really not very far into SDR programming,
> > would like to learn more.
> >
> > I was working with someone who gave me a way forward toward
> > using the same hardware to do the BPSK demodulation, but I want
> > to get his OK before I spread his stuff into this group or other places.
> > And I have not yet done anything with it yet myself.
> >
> >
> > Chris
> >
> >
> > On 10/13/20 9:06 AM, paul swed wrote:
> > > The teensy is on order and downloaded the arduino plugin.
> > > In looking at the code I should mention it does not appear to be a I&Q
> > > sampling. Just a single stream I AM sampler. Though at 60 Khz. Its
> > > essentially a diode with AGC and a slicer to determine a 1 or 0. No
> > matter
> > > a good start in the world of SDR. (At least I do not see an I&Q
> approach)
> > > Regards
> > > Paul
> > >
> > > On Tue, Oct 13, 2020 at 2:47 AM John C. Westmoreland, P.E. <
> > > john at westmorelandengineering.com> wrote:
> > >
> > >> Paul,
> > >>
> > >> Sure - even on my OpenHPSDR system using my vertical antenna - I am
> > almost
> > >> able to decode WWVB (reliably) using the clock
> > >> program from:
> > >>
> > >> http://f6cte.free.fr/index_anglais.htm
> > >>
> > >> with no changes whatsoever.  If I 'fix' the antenna - I'm sure it'll
> > work
> > >> more reliably.
> > >>
> > >> Teensy is Arduino compatible - pretty sure you can use the tools/libs
> > >> fairly easily from Arduino - I don't have a Teensy (yet) but I will
> > >> probably
> > >> get a kit like what's outlined in Chris's post and also here for the
> > people
> > >> that may not be in the US:
> > >>
> > >> https://github.com/DD4WH/Teensy-DCF77 (referenced by Chris in his
> > post).
> > >>
> > >> that describes the antenna circuit in more detail.
> > >>
> > >> 73's,
> > >> John
> > >> AJ6BC
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >> On Mon, Oct 12, 2020 at 8:20 PM paul swed <paulswedb at gmail.com>
> wrote:
> > >>
> > >>> John
> > >>> I would simply use any number of receivers and grab 60 KHz out of one
> > or
> > >>> could use the IF at 10 KHz or 1 KHz. But more fun to use 60 KHz. The
> > cost
> > >>> on the teensy components is very reasonable.
> > >>> Regards
> > >>> Paul
> > >>>
> > >>> On Mon, Oct 12, 2020 at 7:44 PM John C. Westmoreland, P.E. <
> > >>> john at westmorelandengineering.com> wrote:
> > >>>
> > >>>> Hello Time Nuts,
> > >>>>
> > >>>> Chris - maybe you can share that if that's something you can share
> > >> right
> > >>>> now.
> > >>>>
> > >>>> Jim and Paul,
> > >>>>
> > >>>> Like Chris pointed out - on that audio board in the design he's
> worked
> > >>> on -
> > >>>> the Line In has L and R channels - the input resistance is higher
> than
> > >>> for
> > >>>> the mic input -
> > >>>> but I suppose it's possible to try a BPSK implementation using that
> as
> > >> a
> > >>>> starting point.  There's no separate gain stage for the Line In
> inputs
> > >>> like
> > >>>> for the mic - but
> > >>>> it could work - a small preamp that works with the input impedance
> of
> > >> the
> > >>>> Line In circuitry may be necessary to get a good input signal - but
> > >> that
> > >>>> shouldn't be too hard
> > >>>> to add.  Also - do the internals of that chip - the
> > >>>>
> > >>>> https://www.pjrc.com/teensy/SGTL5000.pdf
> > >>>>
> > >>>> really allow the L/R Line In channels to be treated independently?
> If
> > >>> so,
> > >>>> it should be good to go at least for experimentation.
> > >>>>
> > >>>> 73's,
> > >>>> John
> > >>>> AJ6BC
> > >>>>
> > >>>>
> > >>>>
> > >>>>
> > >>>> On Mon, Oct 12, 2020 at 12:07 PM Chris Howard <chris at elfpen.com>
> > >> wrote:
> > >>>>> I received a good pointer about doing the BPSK implementation
> > >>>>> but have just not gotten it done.
> > >>>>>
> > >>>>> Chris Howard
> > >>>>>
> > >>>>>
> > >>>>>
> > >>>>> On 10/12/20 11:02 AM, jimlux wrote:
> > >>>>>> On 10/12/20 7:40 AM, paul swed wrote:
> > >>>>>>> John really appreciate the pointer. Though it doesn't help wwvb
> > >> BPSK
> > >>>>>>> its a
> > >>>>>>> really good intro to SDR and DSP super simple. A good way to get
> > >>> your
> > >>>>>>> feet
> > >>>>>>> wet. Hmmm is there a parts order soon? :-)
> > >>>>>>> Regards
> > >>>>>>> Paul
> > >>>>>>> WB8TSL
> > >>>>>>
> > >>>>>> And the teensy has plenty of space and speed to implement a PLL
> for
> > >>>>>> doing BPSK demodulation.
> > >>>>>>
> > >>>>>>
> > >>>>>>> On Mon, Oct 12, 2020 at 10:33 AM Bob kb8tq <kb8tq at n1k.org>
> wrote:
> > >>>>>>>
> > >>>>>>>> Hi
> > >>>>>>>>
> > >>>>>>>> The “ideal” antenna solenoid would be a bit longer ( say 2 X to
> > >> 5X
> > >>> ).
> > >>>>>>>> The turns should be spaced apart by a few percent of the length.
> > >>>>>>>> ( so turns over 30 or so … not so much …).
> > >>>>>>>>
> > >>>>>>>> How much better is “ideal” compared to “just get it done?”. At
> > >>> least
> > >>>>>>>> from the stories that are told, it is significant. Since all
> > >> these
> > >>>>>>>> antennas
> > >>>>>>>> are very small (so non-ideal) it’s a bit of a snail race.
> > >>>>>>>>
> > >>>>>>>> Bob
> > >>>>>>>>
> > >>>>>>>>> On Oct 12, 2020, at 3:42 AM, John C. Westmoreland, P.E. <
> > >>>>>>>> john at westmorelandengineering.com> wrote:
> > >>>>>>>>> Paul,
> > >>>>>>>>>
> > >>>>>>>>> Doesn't the post by Chris Howard above appear to be a
> good/great
> > >>>>>>>>> starting
> > >>>>>>>>> point?
> > >>>>>>>>> Seems like that approach could be extended.
> > >>>>>>>>>
> > >>>>>>>>> https://github.com/chris-elfpen/Teensy4WWVBsdr
> > >>>>>>>>>
> > >>>>>>>>> 73's,
> > >>>>>>>>> John
> > >>>>>>>>> AJ6BC
> > >>>>>>>>>
> > >>>>>>>>>
> > >>>>>> _______________________________________________
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