Question about noisetypes and ADEV
For those still interested in GPS to WWVB simulation -- after trying a few antenna designs I found that a 50-foot loop of #26 enameled wire stapled to the rafters in the basement works quite well. Putting 35 ma (rms) of 60 kHz WWVB signal through it lights up the house quite nicely. I don't know yet if it also lights up the neighbor's house. I think I will investigate that question when (and if) they pull the plug in Colorado. But I am prepared.
Not so much for my La Crosse Technology WWVB BPSK clock. I think it will get swamped out. Can't have everything, I guess.
Andy Backus
Andy pretty much what I did also. A loop in the basement as suggested by a
time-nut.
Radiations quite low depending on the floor of the house and walls its
100uv to 30 uv.
Did resonate it with a cap that seemed to improve things. But no matter it
works for what I need and the clocks are happy.
I leave the simulator on all of the time now as no matter the time of the
day or battery change the clocks lock in the 3 or so minutes.
Since I don't own an official lacrosse no issue here though perhaps mid
January I will pick one up cheap... Chuckle.
If I do I guess l'll have to build a BPSK version. Oh hang on there thats
what the de-psk-r is. Just add 60 KHz. Actually depending on the clocks
cost as they get dropped maybe not a bad idea. Have fun with your system.
Regards
Paul
WB8TSL
On Sat, Oct 27, 2018 at 6:04 PM Andy Backus ANDREWBACKUS@msn.com wrote:
For those still interested in GPS to WWVB simulation -- after trying a few
antenna designs I found that a 50-foot loop of #26 enameled wire stapled to
the rafters in the basement works quite well. Putting 35 ma (rms) of 60
kHz WWVB signal through it lights up the house quite nicely. I don't know
yet if it also lights up the neighbor's house. I think I will investigate
that question when (and if) they pull the plug in Colorado. But I am
prepared.
Not so much for my La Crosse Technology WWVB BPSK clock. I think it will
get swamped out. Can't have everything, I guess.
Andy Backus
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I should have credited the loop idea as you did, Paul. I don't know who it was, but thank you.
I would leave my translator on all the time if it weren't for my La Crosse -- whose reception would be ruined.
In my system, BTW, a resonant tank precedes a FET amplifier, which provides the antenna current. I have found, as others have, that the frequency must be good to several Hertz. So I use a crystal controlled CMOS gate oscillator to generate the RF.
Andy Backus
WA2TND
From: time-nuts time-nuts-bounces@lists.febo.com on behalf of paul swed paulswedb@gmail.com
Sent: Saturday, October 27, 2018 4:01 PM
To: Time-nuts
Subject: Re: [time-nuts] WWVB Translation
Andy pretty much what I did also. A loop in the basement as suggested by a
time-nut.
Radiations quite low depending on the floor of the house and walls its
100uv to 30 uv.
Did resonate it with a cap that seemed to improve things. But no matter it
works for what I need and the clocks are happy.
I leave the simulator on all of the time now as no matter the time of the
day or battery change the clocks lock in the 3 or so minutes.
Since I don't own an official lacrosse no issue here though perhaps mid
January I will pick one up cheap... Chuckle.
If I do I guess l'll have to build a BPSK version. Oh hang on there thats
what the de-psk-r is. Just add 60 KHz. Actually depending on the clocks
cost as they get dropped maybe not a bad idea. Have fun with your system.
Regards
Paul
WB8TSL
On Sat, Oct 27, 2018 at 6:04 PM Andy Backus ANDREWBACKUS@msn.com wrote:
For those still interested in GPS to WWVB simulation -- after trying a few
antenna designs I found that a 50-foot loop of #26 enameled wire stapled to
the rafters in the basement works quite well. Putting 35 ma (rms) of 60
kHz WWVB signal through it lights up the house quite nicely. I don't know
yet if it also lights up the neighbor's house. I think I will investigate
that question when (and if) they pull the plug in Colorado. But I am
prepared.
Not so much for my La Crosse Technology WWVB BPSK clock. I think it will
get swamped out. Can't have everything, I guess.
Andy Backus
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Andy agreed I wrote about the requirements for stability when I built mine
up.
I did not need to add a amplifier I simply attenuated the output of the
tristate gate to get to the 1000uv level then filtered and split to 6
outputs. One drives the antenna the others drive coax's to truetime and
symetricom clocks. They really look nice. Silly but what the heck.
I agree if I need more power a FET stage is the way to go. Just don't so
far.
Hmmm maybe mid next year I can build a 100 watt amp to cover our town. Not
really. The antenna would be quite a challenge. But I hear I can pick a few
towers up for shipping costs real soon now. Even with matching networks.
Regards
Paul
WB8TSL
On Sat, Oct 27, 2018 at 8:55 PM Andy Backus ANDREWBACKUS@msn.com wrote:
I should have credited the loop idea as you did, Paul. I don't know who
it was, but thank you.
I would leave my translator on all the time if it weren't for my La Crosse
-- whose reception would be ruined.
In my system, BTW, a resonant tank precedes a FET amplifier, which
provides the antenna current. I have found, as others have, that the
frequency must be good to several Hertz. So I use a crystal controlled
CMOS gate oscillator to generate the RF.
Andy Backus
WA2TND
From: time-nuts time-nuts-bounces@lists.febo.com on behalf of paul swed
paulswedb@gmail.com
Sent: Saturday, October 27, 2018 4:01 PM
To: Time-nuts
Subject: Re: [time-nuts] WWVB Translation
Andy pretty much what I did also. A loop in the basement as suggested by a
time-nut.
Radiations quite low depending on the floor of the house and walls its
100uv to 30 uv.
Did resonate it with a cap that seemed to improve things. But no matter it
works for what I need and the clocks are happy.
I leave the simulator on all of the time now as no matter the time of the
day or battery change the clocks lock in the 3 or so minutes.
Since I don't own an official lacrosse no issue here though perhaps mid
January I will pick one up cheap... Chuckle.
If I do I guess l'll have to build a BPSK version. Oh hang on there thats
what the de-psk-r is. Just add 60 KHz. Actually depending on the clocks
cost as they get dropped maybe not a bad idea. Have fun with your system.
Regards
Paul
WB8TSL
On Sat, Oct 27, 2018 at 6:04 PM Andy Backus ANDREWBACKUS@msn.com wrote:
For those still interested in GPS to WWVB simulation -- after trying a
few
antenna designs I found that a 50-foot loop of #26 enameled wire stapled
to
the rafters in the basement works quite well. Putting 35 ma (rms) of 60
kHz WWVB signal through it lights up the house quite nicely. I don't
know
yet if it also lights up the neighbor's house. I think I will
investigate
that question when (and if) they pull the plug in Colorado. But I am
prepared.
Not so much for my La Crosse Technology WWVB BPSK clock. I think it will
get swamped out. Can't have everything, I guess.
Andy Backus
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time-nuts Info Page - lists.febo.com<
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com>
lists.febo.com
time-nuts is a low volume, high SNR list for the discussion of precise
time and frequency measurement and related topics. To see the collection of
prior postings to the list, visit the time-nuts Archives.. Using time-nuts
and follow the instructions there.
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Hi, Tom!
I have looked at the pages you link to many times, they really are very
good - my goal here was to get down to the nitty-gritty myself, just
understand the details better.
Regarding possible bias in the Excel RNG, this was my first hunch as well,
but when I repeated the experiment with W PM data generated in Stable32 I
got similar results. The box-muller code goes in my toolbox, though! :)
Thanks
Ole
On Fri, Oct 26, 2018 at 9:02 PM Tom Van Baak tvb@leapsecond.com wrote:
Ole,
I'm simulating some noise to try to improve my somewhat sketchy
understanding of what goes on with the various noise types as shown on an
ADEV plot. Nothing fancy, ~3600 points of gaussian random numbers
between 0
and 1 in excel, imported into Timelab as phase data, scaled to ns.
I forgot to mention this page where I use Stable32 and TimeLab to look at
all 5 noise types:
You are correct, my statement was imprecise - I generate numbers between
0
and 1, but then multiply that with a function in Excel that yields a
normal
distribution with a standard distribution of 1.
If you suspect problems with Excel, perhaps try something in Python or C
instead.
That also will make it possible to work with millions of points when
necessary.
For random numbers I use ancient code by George Marsaglia, and also
Mersenne Twister 19937.
To convert uniform [0-1] random to Gaussian I use:
// Get normal (Gaussian) random sample with mean 0 and standard deviation 1
// See https://en.wikipedia.org/wiki/Marsaglia_polar_method
double normal (void)
{
// Use Box-Muller algorithm
double u1 = genrand1();
double u2 = genrand1();
double r = sqrt(-2.0 * log(u1));
double pi = 4 * atan(1);
double theta = 2.0 * pi * u2;
return r * sin(theta);
}
/tvb
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Hi, Magnus!
Thank you for this! I am of course nowhere near really comprehending it
from reading it a couple of times, but I will still show my ignorance by
asking a couple of questions with respect to the power law noise table.
Counting on your day being still non-grumpy.. :D
- I notice the formulas for ADEV is different for W PM and F PM - ADEV
does not distinguish between the two, as is pointed out in the article.
Does this not imply a fixed relationship between the power coefficients h1
and h2, such that the results of those to formulas are the same? Or am I
misunderstanding the point of the table? (Also, what is the parameter
y/gamma in the FPM formulas?) - I am not sure I understand the concept of f_H correctly, particularly as
it applies to synthetic data. What is the corner frequency of a random
sequence [0-1]?
Ole
On Sat, Oct 27, 2018 at 11:26 PM Magnus Danielson <
magnus@rubidium.dyndns.org> wrote:
Hi Ole,
I saw this post and thread, but waited until I had the time to address
it sufficiently, as it is an important topic. As such, I really enjoy
you asking the question as I am sure it will be a relevant question for
many more on this list.
On 10/26/18 11:34 AM, Ole Petter Ronningen wrote:
Hi, all
I'm simulating some noise to try to improve my somewhat sketchy
understanding of what goes on with the various noise types as shown on an
ADEV plot. Nothing fancy, ~3600 points of gaussian random numbers
between 0
and 1 in excel, imported into Timelab as phase data, scaled to ns.
I can recommend you and everyone else to use Stable32. You can download
it for free from IEEE UFFC. It not only do analysis, it also do noise
simulations for you.
There is some work to be done on the source code. Uhm, that time.
I mostly get what I expect; "pure" random noise, gives the expected slope
for W/F PM, -1. Integrating the same random data gives the expected slope
for W FM -1/2. Integrating the same random data yet again gives a slope
of +1/2, again as expected for RW FM.
As expected from ADEV yes.
However, looking at the data, I am somewhat baffled by a difference in
the
starting point of the slopes. Given that this is exactly the same random
sequence, I would expect the curves to have the same startingpoint at
tau0.. Clearly not (see attached), but I do not understand why. Any
clues?
Is this some elemental effect of integration (sqrt(n) or some such), or
am
I seeing the effects of bandwidth and/or bias-functions or other
esoterica?
In case the screenshot does not make it though;
W PM starts at 1.69e-9
W FM starts at 9.74e-10
RW FM starts at 6.92e-10
It depends on how the phase-noise slope as multiplied by the Allan
kernel and integrated over all frequencies behave. Each noise type
integrates up to different values for the same type due to the slope.
I prepared a handy table for you when I completely rewrote the poor
excuse of a Wikipedia article that I found for Allan Deviation:
https://en.wikipedia.org/wiki/Allan_variance#Power-law_noise
As you simulate, you need to be careful to ensure that your simulated
noise matches that of the phase-noise slope so you do not get a bias there.
Take a good look at the right-most column. Assume that h_2 to h_-2 all
have the same amplitude, that is the same energy at 1 Hz and we analyze
at the same tau=1s, the numbers will still be different and those comes
from how the integration of those slope works.
The integration is very important aspect, as a number of assumptions
becomes embedded into it, such as the f_H frequency which is the Nyquist
frequency for counters, so sampling interval is also a relevant
parameter for expected level.
I spent quite a bit of time trying to replicate these formulas, and it
taught me quite a bit. If I where a grumpy university professor holding
class on time and frequency, my students would be tortured with them up
and down to really understand them.
For the not so grumpy and non-uni-professor me, I would easily spend a 2
hour lecture on them.
In short, they are not expected to start of at the same level, as the
homework was done we learned that they are not at all expected to start
at the same point. Do use the table as your reference for expected, and
adjust things to learn how to make numbers match up.
The formulas that pops out from all the different variants of Allan
deviation and friends is different for the same slope, tau and f_H
parameters. As we then use say MDEV instead of ADEV, MDEV would fit the
MDEV expected values, but that would have an algorithmic bias to that of
ADEV, which can be estimated quite accurately separately if needed.
The grumpy professor would say, and I would agree, that there is
fundamental differences and they are probably best understood by
studying the many different forms of representations there is for these
measures. Do study the cause of biases, as a sea of mistakes can be
avoided by understanding them.
With that being said, good you caught me on a non-grumpy day. :)
Cheers,
Magnus
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In message CAG15_6tUVY6KvBp=Zt+OP2oP-rORFz16ihDeYGYQUBNYs-ikGQ@mail.gmail.com, Ole Petter Ronningen writes:
- I notice the formulas for ADEV is different for W PM and F PM - ADEV
does not distinguish between the two, as is pointed out in the article.
When we say ADEV does not distinguish those, we mean that the slope of
the ADEV with respect to tau is the same, not that the ADEV is the same.
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
Hej Ole!
On 10/28/18 9:19 AM, Ole Petter Ronningen wrote:
Hi, Magnus!
Thank you for this! I am of course nowhere near really comprehending it
from reading it a couple of times, but I will still show my ignorance by
asking a couple of questions with respect to the power law noise table.
Please ask.
Counting on your day being still non-grumpy.. :D
:-D
- I notice the formulas for ADEV is different for W PM and F PM - ADEV
does not distinguish between the two, as is pointed out in the article.
Does this not imply a fixed relationship between the power coefficients h1
and h2, such that the results of those to formulas are the same? Or am I
misunderstanding the point of the table? (Also, what is the parameter
y/gamma in the FPM formulas?)
The trouble is that the mathematical difference as you see in the table
is very very hard to make use of, as you have two functions with almost
the same shape, and the difference between them is small, so small that
the confidence interval for the noisy type of data make it hard to
extract the difference with any form of useful trust in the numbers. Add
that you have other forms of disturbances which isn't pure noise. For
most practical purposes they are indistinguishable using ADEV and this
annoyed David Allan for 15 years until he finally could present the
modified Allan, which is "the one" for him, as it is more complete in
the noise separation aspect, which was the driver for his work in the
first place.
So, the table is correct, but not very useful in this regard.
Remember that it is noisy data, and for any finite series of noisy data,
there is practical limits to how much we can derive out of them. We keep
inventing better tools to gain precision, reduce processing, reduce
length of measurement etc. Thus, theoretical differences may turn out
not be very useful in the practical world, so we need to do things in a
way that is practical.
When using MDEV you has an algorithmic bandwidth that change, which so
for higher tau you have a more narrow-band filter, which makee white
phase noise change amplitude much faster than flicker phase noise, and
hence the distinction can be made.
As you move over to parabolic deviation, it has even steeper filter and
thus suppress noise even more. This helps to explain the improved
performance of regression based frequency estimation.
So, ADEV is far from the right tool for everything. In fact, it is
greatly misused.
- I am not sure I understand the concept of f_H correctly, particularly as
it applies to synthetic data. What is the corner frequency of a random
sequence [0-1]?
If you say that your samples is at tau_0=1s, then the sample-rate
becomes f_S = 1/tau_0 = 1 Hz and the f_H becomes f_H = f_S * 1/2 = 1/2 Hz.
Cheers,
Magnus
I made a revised figure with a few improvements:
- the PSDs now cross at 1Hz
- the theoretical ADEV/MDEV pre-factors are now explicitly stated
http://www.anderswallin.net/2018/10/noise-colours-again/
source:
https://github.com/aewallin/colorednoise/blob/master/example_noise_slopes2.py
I forget where the MDEV-coefficients come from - maybe the Dawkins et al.
paper? (worth adding to wikipedia also?)
Also for flicker-PM there seems to be (slightly) different versions of the
ADEV pre-factor in different references.
Anders
On Sat, Oct 27, 2018 at 10:08 AM Anders Wallin anders.e.e.wallin@gmail.com
wrote:
Is this some elemental effect of integration (sqrt(n) or some such), or am
I seeing the effects of bandwidth and/or bias-functions or other
esoterica?
FWIW the python "colorednoise" (aka. Kasdin-Walter) repo has a figure:
https://github.com/aewallin/colorednoise
and code that generates the figure:
https://github.com/aewallin/colorednoise/blob/master/example_noise_slopes.py
Good morning all,
Some people may remember the Arduino code I wrote for controlling and
monitoring the TruePosition GPSDO I wrote in mid-2017.
I've updated that code to include a couple of new things:
- now gets the store LAT/LONG/ALT and displays it
- adds an LED that lights up when STAT=0 (locked)
- adds in the ability to command a survey, and monitor the survey
If interested, it can be downloaded here:
http://www.kd5byb.net/TruePosition/TruePosition_rev_21.zip
As usual, keep in mind I'm not a professional programmer, the code is
probably full of bugs, errors, and silly things that a profession
programmer would look at and say "what the heck is he doing?" ;)
thanks,
ben