Dear Gilles,
If I understand you correctly you will take the French time signal at
162 kHz and divide the frequency with 81 in an attempt to compare two 2
kHz signals, one originating from the time signal, and another from an OCXO.
However, I would advice not to take the 162 kHz signal and try to divide
it with 81. The 162 kHz signal you pick off the air is an analog signal,
and it will suffer from all kinds of unwanted noise, dips and multipath
phenomena. I assume you plan to condition the signal so that you can
feed it to a digital divider. However, this is an invitation to cycle
slips and jumps.
An off-air frequency reference receiver like the Halcyon OFS-1 fed an
amplified and filtered 162 kHz signal directly to a divider, and the
resulting performance was awful. Take a look at
https://dabbledoo.weebly.com/halcyon-ofs-1.html
If you live very close to the transmitter site, it may work to condition
and then divide the 162 kHz signal, but if not, you will not be happy.
Best regards
Ole
Den 21-06-2020 kl. 09:30 skrev Gilles Clement:
Hi,
Comparing a reference signal at 162kHz with local 10MHz ocxo. Expected Adev
10E-11 at 10sec.
162kHz / 81 = 2kHz = 10MHz / 5000
GC
Le 21 juin 2020 à 05:49, Bob kb8tq <[email protected]> a écrit :
Hi
*Any* divide approach followed by a flip flop clocked by the input clock will
meet
that same basic requirement. While it *sounds* like it would improve things, it
very much depends on the details.
What are you trying to do? What is the input frequency? What is the phase noise
requirement?
Bob
On Jun 20, 2020, at 2:22 PM, Gilles Clement <[email protected]> wrote:
Hi Robert,
You are right, its the lambda divider that was discussed. Need to better
understand this approach....
74HC40103 could also do the 81 Pi-divide easily, but I tend to prefer the
PICDIV concept where the controller is clocked by the signal to divide (So
limited or no noise is added). AVR family could do it, as most of the
instructions take only one clock.
Gilles.
Le 20 juin 2020 à 19:48, Robert LaJeunesse <[email protected]> a écrit :
Gilles, if I read the Calosso-Rubiola paper correctly a Pi divider is pretty
much your standard square-wave producing digital divider, such as a 74163 (for
even divides). There's odd-value (3,5,7) Pi dividers shown at
https://www.theremin.us/Circuit_Library/symmetrical_digital_dividers.html. What
the Calosso-Rubiola paper promotes is the Lambda divider, which is depicted in
figure 2 of the paper.
Bob L.
Sent: Friday, June 19, 2020 at 10:27 AM
From: "Gilles Clement" <[email protected]>
To: "Poul-Henning Kamp" <[email protected]>
Cc: "Discussion of precise time and frequency measurement"
<[email protected]>
Subject: Re: [time-nuts] Frequency division by 81
Hi,
Could you point me to a practical design example of a Pi divider ?
Envoyé de mon iPad
Le 19 juin 2020 à 08:56, Poul-Henning Kamp <[email protected]> a écrit :
--------
I need to divide the output of an OCXO by a factor D=81 for testing purposes.
So with minimum added phase noise.
Two stages of divide by 9 PI-dividers ?
http://rubiola.org/pdf-articles/conference/2013-ifcs-Frequency-dividers.pdf
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
[email protected] | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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