[time-nuts] WWVB teensy BPSK early experiments

Tue Nov 10 18:36:01 UTC 2020

Graham that is the alternate approach. The new suggested KD2BD vcTCXO works
very well. Its 10 MHz and readily available. But then the old divider
chains are needed. The KD2BD method works well if you have plenty of solder.
First mixer is 50 KHz LO. Result 10 KHz IF.
10 KHz IF gain
Second Mixer is a 10 KHz LO results in a 0 Hz IF.
But the products are actually phase offset and bit.
The above comments are seriously over simplified.
Having built the KD2BD receiver I am interested in a low solder solution.
:-)
Really have to do far more experimentation. The teensy is very powerful.
Regards
Paul

On Tue, Nov 10, 2020 at 12:56 PM Graham / KE9H <ke9h.graham at gmail.com>
wrote:

> Paul:
>
> It might be easier to relegate that function to hardware.
> A simple TC-VCO that drives the sampling clock for the ADC and is steerable
> for frequency/phase lock from the CPU would allow you to build a
> synchronous receiver without working about locking the CPU clocking system
> to anything.
>
> --- Graham
>
> ==
>
> --- Graham
>
> On Mon, Nov 9, 2020 at 8:06 PM paul swed <paulswedb at gmail.com> wrote:
>
> > No time to experiment the last few days as the weather has been great and
> > have to get outside stuff done. That said trying to tease apart how to
> > create a lockable NCO in the teensy.
> > Its not clear to me that I can create a sine wave oscillator and drive
> that
> > out to a pin to see stability and adjustment effects. It can be done by
> > mixing with another internal signal and measuring the output. But my
> > preference would be direct measurement.
> > With respect to sine and cosine. It seems a second oscillator and a third
> > oscillator that is 90 degrees out can be created. Supposedly these would
> be
> > locked. (To be proven)
> > Regards
> > Paul
> >
> >
> > On Sun, Nov 8, 2020 at 7:59 PM John C. Westmoreland, P.E. <
> > john at westmorelandengineering.com> wrote:
> >
> > > Hello Graham and Fellow Time Nuts,
> > >
> > > I did what Paul had mentioned as well - and that appeared to clear up
> the
> > > immediate screen issues but I will
> > > insert a termination resistor as well as Graham has suggested.
> > >
> > > I looked on the PJRC forum as well - and it appears there has been a
> lot
> > of
> > > discussion and development regarding
> > > the enhancement of the performance of these TFT displays - also -
> > there's a
> > > beta version of the arduino libraries -
> > > Teensyduino 1.54 Beta #4 -
> > > https://forum.pjrc.com/threads/64303-Teensyduino-1-54-Beta-4 - take a
> > look
> > > at that
> > > for those that are experimenting with this platform.
> > >
> > > As far as my current setup - in the wee hours today - the WWVB signal
> was
> > > coming in very strong - my HPSDR rig
> > > using the Clock tool from Multipsk was decoding every minute - the
> Clock
> > > programs' PLL was solidly locked.
> > >
> > > I noticed for the Teensy4WWVBsdr code it appeared to be in sync with
> > WWVB -
> > > it was decoding either a minute or
> > > the hour apparently correctly - but it was shifted - meaning say for:
> > >
> > > 2:38:00 AM it decoded 2 as the minute - which was incorrect but correct
> > for
> > > another time position
> > >
> > > or, for the hour it would say 8 as hour.  This makes me think obviously
> > for
> > > some reason the positions are being
> > > shifted in an otherwise somewhat successful decode attempt.
> > >
> > > I am using the Teensy 4.1 - I need to check all of the libs to make
> sure
> > > nothing incompatible is possibly taking place.
> > >
> > > I've been informed also the antenna from Stormwise is on the way.
> > >
> > > Thanks again Graham - KE9H - for helping out on this.
> > >
> > > 73's,
> > > John
> > > AJ6BC
> > >
> > >
> > > On Sun, Nov 8, 2020 at 8:02 AM Graham / KE9H <ke9h.graham at gmail.com>
> > > wrote:
> > >
> > > > John W:
> > > >
> > > > Regarding your Teensy WWVB receiver display issues.
> > > > The Teensy does not have a source termination resistor on the SPI
> > clock.
> > > > Add a 50 Ohm resistor (value not critical, anything from 33 to 75
> will
> > > > work) in series with the SPI Clock signal, as physically close to the
> > > > Teensy as practical.
> > > > This totally cleared up all of my display issues.
> > > >
> https://www.analog.com/media/cn/training-seminars/tutorials/MT-097.pdf
> > > > Source termination resistors provide a source resistance to absorb
> the
> > > > reflection of fast edges off the slave device input, reducing all the
> > > > bouncing and wiggles on the rising and falling edges of signals,
> > > > particularly important/beneficial on clock signals.
> > > >
> > > > --- Graham
> > > >
> > > > ==
> > > >
> > > >
> > > > On Wed, Nov 4, 2020 at 10:55 AM John C. Westmoreland, P.E. <
> > > > john at westmorelandengineering.com> wrote:
> > > >
> > > > > Paul/Chris,
> > > > >
> > > > > Also - in addition to the white screen, I get this sometimes after
> > > > running
> > > > > for a while - have you guys seen this?
> > > > >
> > > > >
> > > > >
> > > >
> > >
> >
> https://user-images.githubusercontent.com/2308903/98118247-cd4c7b00-1e5f-11eb-8510-aa1ed0beba52.jpg
> > > > >
> > > > > 73's,
> > > > > John
> > > > > AJ6BC
> > > > >
> > > > >
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