[time-nuts] WWVB Dephaser Question

Sat Oct 17 09:53:27 UTC 2020

Hello Time Nuts,

Maybe this should be added to this thread - this page is actually pretty
good:

https://en.wikipedia.org/wiki/WWVB

73's,
John
AJ6BC

On Tue, Oct 13, 2020 at 12:50 PM John C. Westmoreland, P.E. <
john at westmorelandengineering.com> wrote:

> 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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