[time-nuts] WWVB Dephaser Question

[paul swed]

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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