[time-nuts] wwvb d-psk-r updated general purpose reciever

Clint Turner turner at ussc.com
Fri Nov 1 22:06:12 UTC 2013


When I was messing with my SkyScan WWVB clocks to determine if something 
that WWVB's signal had done "broke" them, preventing them from setting 
properly and so-doing, I wanted to see what the receiver module was seeing.

(Spoiler:  They didn't - they just break if the date is something later 
than approx. August, 2012 - I mentioned this some months ago on this 
list, providing a link to a blog entry where this was discussed in detail.)

What I did to see what the clock chip was seeing via a 'scope was to 
hang a JFET source follower on the "narrow" (downstream) side of the 
60.003 kHz bandpass filter crystal coupled with a small value cap and a 
with a 10 meg resistor from the gate to ground:  That didn't seem to 
adversely affect performance, and I could see the phase flopping back 
and forth.  (The signal was pretty low - but usable.)

At that point the AM was still present, so the "key up" portions of the 
waveform were expectedly weaker - but it seemed to me at the time that I 
could have used it for something more complicated down the line.

What I was thinking at the time, were I to proceed farther, would have 
been to take that buffered signal off-board, amplify it a bunch and then 
run it through a limiter.  In theory, this - along with the demodulated 
time code - would have provided both the amplitude and phase components.

Clint
KA7OEI

On Fri, 1 NOV 2013 saul swed said:
> Hello to the group. It has been a while since I have sent anything. The
> last was the wwvb regenerator for time clocks.
> However I have been working on a general purpose wwvb receiver. One that is
> inexpensive, uses parts available today, is inexpensive, single supply, low
> power, and uses parts I don't need a microscope for. There are lots of
> older designs out there and at least one quite nice design is by one of our
> fellow time-nuts that started me thinking. But many of the designs use
> inductors that have become difficult to obtain.
> As much as I would have loved to hack one of the one chip wwvb clock chip
> wonders they simply did not work out. They are hot receivers actually
> because there was no way to pull the amplified wwvb signal out. Tried a
> number of schemes like 2 chips in parallel. One detecting the AM signal and
> providing AGC control to chip 2 that had no AGC or demod caps.
<snip>





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