[time-nuts] WWVB PM Time Questions

[paul swed]

Mark you really are in the right place. The fact is Time-nuts has a huge
range of skill sets.
To your question. Can't resist "No pain no gain".
The KB2DB design is a good and very real design. I have built it and it is
whats needed when you are receiving 60 KHz covered in all kinds of noise
these days. Also look at some of the older designs like spectracoms. You
can get those schematics online.
My antenna in Boston is a 10' X 10' square loop and preamp some 800' of
wire or 400? Been a bit of time. It gives me very nice signals in the day
time 100 uv or more level and at night crazy high levels 300-600 to 1000 uv.
The loop can be turned to reduce noise.

You don't need a loop that big. But I have been very happy with it over the
last 7 years.
The challenge today is that way back when you could buy real transformers
and crystals to make very good TRF radios. Thats all gone so OP-amps it is
and a hot soldering iron. Ah the smell of flux in the morning.
I did build a radio with the little 60 KHz crystals you can buy for $2 or
so from China. A bag of 20. Sorted through them looking for a reasonable
unit to use. The bandwidth required is about 2 Hz. You can go wider and a
pure opamp solution will be wider. It just allows more noise in.
So get that soldering iron out and feel the pain. I for one want to watch
the dsp side of what you do on a STM32. Good luck.
Regards
Paul
WB8TSL

On Thu, Jul 23, 2020 at 3:56 PM Mark Haun <mark at hau.nz> wrote:

> On 23-Jul-20 4:35 AM, Detlef Schuecker via time-nuts wrote:
> > Hi,
> >
> >> principles.  The STM32L4 series which I often use has a pretty decent
> >> ADC: fast (5 MSPS), with about 11 good bits in differential mode, and
> >> "proper" hardware downsampling (called the DFSDM in the manual).  If the
> > Yes, the STM32 series also have built-in OPAmps, so one could hook up a
> > loop or a ferrite directly to the uC without too much external
> components.
> > Sampling at 160ks/s should suffice to get the phase and DCF77 is in
> reach
> > as well. At this rate you have ~500-1000 processor ticks per sample
> which
> > should be enough to do real time demodulation.
>
> Are there any examples (schematics) out there for the front-end
> electronics?  I haven't found much by googling except the KD2BD design
> which is more involved than I would like.  The integrated designs used
> in "atomic" clocks seem very simple, but I am unsure how to duplicate
> them.  I would like to use a crystal filer, but I'm at a bit of a loss
> to start.  For example, would one choose series or parallel resonance?
> I believe the impedance of these tuning forks is quite high at series
> resonance---tens of kohms.  I didn't make much progress the last time I
> tried doodling op-amp circuits to use one.
>
> My general impression of this list is that a lot of folks are pretty
> comfortable with analog and discrete digital design, but find DSP and
> algorithms "hard."  I'm exactly the opposite so maybe I am in the right
> place ;)
>
> Mark
>
>
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