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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