[time-nuts] WWVB teensy BPSK early experiments

[John Ackermann N8UR]

Just a thought, Paul --

If the teensy can generate an output that is accurate but jittery, you 
could use a simple PLL to lock a crystal to that with a time constant 
that smooths out the jitter.

John
----
On 10/31/20 1:47 PM, paul swed 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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