[time-nuts] WWVB Dephaser Question

[paul swed]

John had not seen this before. It is a AM decoder. But its an interesting
start if you are less than 1000 miles from wwvb.
Regards
Paul

On Mon, Oct 12, 2020 at 6:52 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
>
>
> On Sun, Oct 11, 2020 at 9:23 AM paul swed <paulswedb at gmail.com> wrote:
>
> > Good morning to the group. Both Rodger and I can answer the last question
> > on the questionable bits very well.
> > I have 7 antique devices spectracoms truetime fluke tracor Dymec etc.
> > They handle it very well each has at least a 2 second integration time.
> The
> > dpskr has always taken advantage of this fact. Literally we have run days
> > without flips in the charts. Even in summer.
> > Some surprises in doing this. Numbers of bits that could change don't
> seem
> > to. Then some of the bits have a really odd pattern but they follow the
> > pattern. Thats been coded into the dpskr. In fact anything over several
> > years we have figured out are coded in.
> > One thing we did not do was automatic change from summer to winter
> offsets.
> > Its really a PIA so just not that excited when this happy switch flipper
> > can do it in 1 second.
> >
> > The other bit of fun for the magical new DPS wwvb receiver is after you
> get
> > the bits you must decode them and its nothing like the AM code. Its a M/N
> > FEC code. Its all in the NIST papers but was fun coding and I imagine
> every
> > bit as fun decoding. The dpskr software at least gives you hints to the
> > process.
> >
> > Here is an offer. Anyone that gets the BPSK bits working through a
> SDR/DPS
> > arduino/STM cheap chip. Please no $100 FPGA development kits.
> > I will be happy to dig into the decoder. The solution needs a 1pps and
> the
> > bit.
> > Whats really funny about the wwvb bpsk is that there has never been sort
> of
> > a open development platform. Anyone who has played with the ES100 will
> run
> > into some issues that are annoying for a time nut to tinker with.
> > Regards
> > Paul
> >
> > On Sun, Oct 11, 2020 at 10:39 AM Bob kb8tq <kb8tq at n1k.org> wrote:
> >
> > > Hi
> > >
> > > The “simple” approach is to generate the full modulation pattern
> > > for the signal based on a “known good” time source. There are a
> > > couple of ambiguous  bits so it will only be close. Feed that into
> > > your inverter and the result will be (near) clean WWVB. Since you
> > > never demodulate the WWVB, there isn’t a lot to the RF side ….
> > >
> > > There will be some drops and pops. The question will be just how
> > > well this or that antique device deals with them.
> > >
> > > Bob
> > >
> > > > On Oct 10, 2020, at 10:01 PM, paul swed <paulswedb at gmail.com> wrote:
> > > >
> > > > The additional article John sent us is a pretty good read. Having
> > > soldered
> > > > all the little wires together with heat shrink, I can see the
> advantage
> > > of
> > > > the epoxy approach.
> > > >
> > > > A consideration for the discussion. So far its been about the various
> > > tried
> > > > and true methods for a RF frontend. But the real challenge that is in
> > > front
> > > > of us is the software that uses that frontend. How about a very easy
> to
> > > > build a phase flipper so that those that are software inclined do not
> > > need
> > > > to deal with the frontend to get going. The dpskr has a phase flipper
> > in
> > > it.
> > > > But it can be even simpler than that.
> > > >
> > > > A 60 KHz logic signal ( divide 6 Mhz down or anything else thats
> easy)
> > > > Feeds an inverter to generate the 180 degree phase. A gate to select
> 0
> > or
> > > > 180 degrees. All of the gates/inverters can actually be a single quad
> > > > nand gate. A D flip flop with the clock from the 0 degree 60 KHz
> logic
> > > > level. Your data into the D input. The D flip flop synchronizes the
> > data
> > > to
> > > > the clock. On the output you can filter the signal or not and cut the
> > > level
> > > > down or not.
> > > > Its a BPSK source.
> > > > Granted in a pure gate approach the actual bpsk flip will not be the
> 2
> > X
> > > 60
> > > > KHz for 1/2 cycle. But in real receivers the 120 KHz never comes
> > through
> > > > the various stages and filters. So no real harm. This also doesn't
> > supply
> > > > the AM signals 14-17 db modulation. But its good enough to allow
> > software
> > > > to be developed and its simple.
> > > > Good luck
> > > > Paul
> > > > WB8TSL
> > > >
> > > > On Sat, Oct 10, 2020 at 2:05 PM John Magliacane via time-nuts <
> > > > time-nuts at lists.febo.com> wrote:
> > > >
> > > >> For WWVB reception, I use a single turn of 40-conductor ribbon
> cable,
> > > >> configured as a 40-turn loop, brought to resonance with a parallel
> > > >> capacitance, that differentially drives an instrumentation
> amplifier.
> > No
> > > >> electrostatic shielding is needed to eliminate e-field pickup with
> > this
> > > >> approach.
> > > >>
> > > >> The antenna hangs in my attic with thumbtacks and does a commendable
> > > job,
> > > >> day or night, 1622 miles east of WWVB.  See attached JPEG image.
> > > >>
> > > >> The March 2017 issue of "Circuit Cellar" magazine described an
> > > "improved"
> > > >> version of my antenna/preamp combination (which I haven't looked
> > into).
> > > >> See attached PDF document.
> > > >>
> > > >> During my early experimentation, I realized that the preamp would
> need
> > > to
> > > >> have a high dynamic range in order to perform well in the high-noise
> > > >> environment that is LF.   And if the preamp is going to feed a
> > receiver
> > > >> through any reasonable length of coax, it will need to be able to
> > drive
> > > a
> > > >> high capacitance load as well.
> > > >>
> > > >>
> > > >> 73.000 de John, KD2BD
> > > >> _______________________________________________
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