[time-nuts] WWVB teensy BPSK early experiments

[rcbuck at atcelectronics.com]

Thanks John.

Ray,
AB7HE

-------- Original Message --------
Subject: Re: [time-nuts] WWVB teensy BPSK early experiments
From: "John C. Westmoreland, P.E." <john at westmorelandengineering.com>
Date: Sat, October 31, 2020 9:06 pm
To: Discussion of precise time and frequency measurement
<time-nuts at lists.febo.com>

Ray,

https://github.com/chris-elfpen/Teensy4WWVBsdr

73's,
John
AJ6BC


On Sat, Oct 31, 2020, 18:31 <rcbuck at atcelectronics.com> wrote:

> Bob,
>
> "Things already accomplished by Chris in the wwvb AM receiver"
>
> Is there a link to the AM receiver? Curious as to what that looks like.
>
> Ray,
> AB7HE
>
> -------- Original Message --------
> Subject: Re: [time-nuts] WWVB teensy BPSK early experiments
> From: Bob kb8tq <kb8tq at n1k.org>
> Date: Sat, October 31, 2020 11:42 am
> To: Discussion of precise time and frequency measurement
> <time-nuts at lists.febo.com>
>
> Hi
>
> …..errr…..
>
> Can you pull the clock oscillator off the Teensy board? (Yes, the
> soldering
> iron would be involved).
>
> Will the clock input to the MCU accept something like 10 MHz? If so
> solder
> on a cable ….
>
> At that point whatever the Teeny does is locked to the 10 MHz. If that
> comes
> from one of the $3 eBay OCXO’s, steer that with a DAC output … now
> you
> have a WWVB GPSDO.
>
> Indeed, if the Teensy needs 28 MHz, then the OCXO will not be quite as
> cheap.
>
> Bob
>
> > On Oct 31, 2020, at 1:47 PM, paul swed <paulswedb at gmail.com> wrote:
> >
> > Hello to the group. Wanted to update the everyone thats interested in
> > what I have learned so far on the Teensy and audio codec. No complete
> > solution yet. Much of my experimentation and knowledge has come from
> Frank
> > and Chris, who built the complete wwvb AM time receiver. In addition
> > and important is Johns KD2DB BPSK receiver. There is a reason this
> matters.
> >
> > The teensy combination is powerful and somewhat easy to use. (Has to be
> for
> > me). So over the week or so it's been getting used to the audio libraries
> > and how pieces are connected in software and then seeing the results. All
> > of the base experiments worked very quickly. Simple things like signal
> > generators, multipliers and filters. Things already accomplished by Chris
> > in the wwvb AM receiver.
> >
> > But the question really is what to accomplish?
> > If its the wwvb bpsk timecode. Simply buy an ES100 and be done.
> >
> > The interest that I have is a locked reference. Minimizing soldering and
> > construction. This is the point things get interesting.
> > A NCO can be created in Teensy but it tends to be low frequency and a
> > multiple of 60 KHz. Stability sort of isn't. But if it could be created
> > then a complete frequency reference in the teensy could be accomplished.
> > That makes for a heck of a low power receiver 1 watt, inexpensive, and
> > little soldering.
> > The above path literally follows the old Spectracoms and Truetime direct
> > conversion receivers.
> > Have to look at their schematics because they do lock a useful reference.
> > But that means something external has to come into the teensy. Get the
> > soldering iron hot.
> >
> > The other approach is essentially Johns KD2BD receiver in software with
> an
> > external reference chain delivering 50KHz and 10 KHz to the teensy. Well
> > this is getting ugly now because that external chain is made up of a
> > classical divider 10 MHz to 50 KHz etc. But does give a very nicely
> locked
> > useful wwvb reference. Its really a hybrid because it significantly
> reduces
> > the soldering required in a true KD2BD receiver but isn't the pure in
> > a chip solution.
> >
> > All of this is just for fun because the fact is the GPDSOs we use are
> > better.
> > If a receiver is built a natural by-product is the time message. Its just
> > not my focus or interest.
> > Much more to learn.
> >
> > Next steps
> > Start to reuse the wwvb teensy AM receiver.
> > Chop out all of the display software. Its all very nice but for me at
> this
> > stage gets in the way of understanding things.
> >
> > With respect to I&Q generation several suggestions have been made. But
> the
> > teensy supports multiple multipliers. Sort of thinking, use the sine
> > wave oscillator and add a 90 degree delay to a second path to a second
> > multiplier. An alternative inject the delay in the wwvb signal also. How
> > fine a delay is a serious question.
> > Much to learn and potholes to fall into.
> > Regards
> > Paul
> > WB8TSL
> > _______________________________________________
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