thank you for that info, 2kHz bandwidth is a big problem for me, since a
very strong -- approx 20dB above the desired -- and not so stabile
carrier is just 700 Hz away --upward -- from the desired 60kHz, a to
narrow bandwidth is also a problem since it converts the phase
modulation into amplitude modulation -- the filter has to change the
phase, for 180° phase change it needs approx two times the Q times
period time....that "trick " makes the "atomic clocks" with crystal
filter also crazy., the "see" some unexpected characters
Apropos atomic clocks, there is no usable available chip on the market
which would work....
Question, what was the goal to introduce that new modulation schema?
Since the new modulation scheme caused more trouble than usable result,
could it happen, that it will disappear?
73
Alex
On 6/29/2014 10:08 AM, John Reed wrote:
Thanks Paul. I thought that this would be a simple project. But, I'm
seeing that random phase jump problem on every method I've tried so
far. My first attempt was a 2N2222 that would go into saturation on
the plus cycle, then into a flip-flop. I ended up with the phase
problem on the 60 KHz output. Then I tried using a pulse generator
into a flip-flop. Same problem. The puzzling thing is the 120 KHz
output from the 2N2222 or pulse generator look fine, but the 50 KHz
output of the flip-flop is not.
By the way, my 5 section synchronous filter is an LC with op-amps
between each stage to bring the gain up for the squaring chip. It has
a 2 KHz -6 dB bandwidth at 60 KHz.
John
-----Original Message----- From: paul swed
Sent: Sunday, June 29, 2014 9:34 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Dephasing WWVB
John welcome to time nuts. This won't be a super long post have other
things to do.
Search for d-psk-r and you can see a few of my exploits. Summation. "It
ain't easy".
It appears to be really easy unless you are far away like the east coast.
Then the propagation gods enter into the picture along with the 60 KHz
station in England that shows up most nights.
The simplest of approaches was indeed the old doubling trick and the many
flavors of it. I built most along with regenerative dividers and other
trickery. Fact is it simply drops a count and that flips the phase quite
annoying.
I finally created two approaches. One specifically for spectracom devices
essentially adding a third mixer and checking for the flip. Works but
requires internal hacking of the spectracom.
The other pretty much a freestanding receiever using a classic costas
loop
approach. All details were released to time nuts over a year ago.
My next stab is more of a digital approach using the STM discovery board.
Have to say I seem to get lost in some of the basics of getting all of
the
crazy registers set.
However its value is it can run very very fast. So you can do some nice
sampling.
Regards
Paul
WB8TSL
On Sat, Jun 28, 2014 at 5:38 PM, Charles Steinmetz
<csteinm...@yandex.com>
wrote:
John wrote:
I discovered an article on the web that uses an AD835 multiplier
chip to
square the WWVB signal * * *. I built a five section synchronous
filter
tuned to 60 KHz to get rid of interference and its output feeds the 835
chip. This all works fine. * * * the 599J won't tune that high
so I
have to divide this 120 KHz frequency by 2. * * * I've tried to
generate a pulse train from the 120 KHz signal and then use a
flip-flop to
divide the frequency. This does not work well. Apparently
generating the
pulse train picks up noise and I end up with a 60 KHz signal with
fluctuating phase. Now I'm trying to get a Miller frequency divider
working
Why are you trying to generate pulses, rather than just squaring
(clipping) the output of the 835 in a saturated amplifier? Pulses have
less energy and therefore higher noise. All you need is a
signal-conditioning squarer matched to the level coming out of the
835 (see
Bruce Griffith's pages at <ko4bb.com> for ideas, as well as the Wenzel
site and any number of illustrations in Experimental Methods in RF
Design
-- for example, both Figures 5-46 and 4-45 show complete simple squarers
with FF dividers). Even a CMOS gate biased to half-voltage should work
fine. I like the NC7SZ74 Dflop for the divider. Half of a 74HC74 works
fine, too.
This should be the kind of thing you throw together in 15 minutes and it
works first time.
Best regards,
Charles
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