On 1/12/17 10:52 PM, Ole Petter Ronningen wrote:
Hi, all
The question of phase shifts in cables pops up every now and then on this
list - I stumbled across a good table of measured phase shifts with
temperature in different cable types in this paper:
http://www.ira.inaf.it/eratec/gothenburg/pres
Hi
There’s an interesting comment buried down in that paper about limiting ADEV to
< 300 samples per point. Their objective is apparently to better highlight
“systematic
errors”. I certainly agree that big datasets will swamp this sort of thing. I’m
not quite
sure that I’d recommend ADEV to fi
While probably not tight enough for time nuts use, there is a new WiFi
technology shown at CES that provides time sync between nodes to allow audio to
be simulcast over many locations. the info (in short form) is here for those
interested:
http://electronicdesign.com/embedded/upgrade-wi-fi-pr
they were really short on hard details about this new technology.
the *WiFi alliance* website only shows this off-site article link I found under
NEWS:
http://www.rcrwireless.com/20170104/test-and-measurement/20170104test-and-measurementwi-fi-alliance-to-certify-timesync-among-multiple-devices-
Hi
A lot depends on how much “less than a microsecond” the chip sets really
deliver in the real world. If they get down into
the sub 100 ns range (which they might), it’s a very useful thing for relaying
GPS data from a roof antenna down to an
NTP server in the basement. 1588 is a “less than a
Hi Corby,
I an looking your Pressure Compensation for the HP5065A ad I have a question
about the preliminary adjustment of R3.
Can you give me the alignment procedure you have used?. I suppose you have
used the Pressure chamber looking at the frequency offset.
thanks,
Luciano
Hi
Just for reference, I happen to be running a ping over my local WiFi to one of
the switches
on the LAN. The ping response is anywhere from 2 ms out to 400 ms. Most of the
time it’s
in the 3 to 9 ms range. Simply taking that down to < 1 us would be a really big
deal.
Bob
> On Jan 13, 2017
On Fri, January 13, 2017 10:59 am, Bob Camp wrote:
> 1588 is a "less than a microsecond" sort
> of approach that does indeed get down to nanosecond
> sort of levels. This could be similar.
There was talk of adding a wireless profile into 1588 either as an
addendum or as part of PTPv3. I suspect t
I saw this article too -- is anyone aware of something with more
technical details? For example, where in the protocol stack does it
work? Is it specific to 802.11 or general purpose ethernet?
Speaking as someone who has a primary hobby of the development of
super low cost time sync algorithms a
I think you might be overthinking their point, that if you plan to use an
xDEV as a measure for state of health, don't use years worth of data.
Otherwise it could be days before the xDEV visually changes.
On Fri, Jan 13, 2017 at 11:04 AM, Bob Camp wrote:
> Hi
>
> There’s an interesting comment b
Hi
I do agree with their point that systematics will get buried in giant data
blocks.
What I’m not quite as sure of is the utility of even 300 sample blocks to spot
systematic issues.
Bob
> On Jan 13, 2017, at 1:08 PM, Scott Stobbe wrote:
>
> I think you might be overthinking their point, th
> On Jan 13, 2017, at 09:40, Bob Camp wrote:
>
> Just for reference, I happen to be running a ping over my local WiFi to one
> of the switches
> on the LAN. The ping response is anywhere from 2 ms out to 400 ms. Most of
> the time it’s
> in the 3 to 9 ms range. Simply taking that down to < 1 u
You are certainly justified to be cautious of only using an xDEV for state
of health. I don't know what GPS does for example to mark SV's as healthy
or not healthy.
On Fri, Jan 13, 2017 at 1:11 PM, Bob Camp wrote:
> Hi
>
> I do agree with their point that systematics will get buried in giant dat
Hi
I probably should have added that I already know that the switch will do sub 1
ms
LAN pings all day long with the near zero load that it’s running. Sorry about
that.
Now, there certainly are OS level things on my laptop that will muck up pings.
Unfortunately
they also get into a number of
I recently made a change in Lady Heather's satellite signal maps to help with a
very similar issue. Before, the maps were based upon the accumulated average
value of the sat signals at each point in the sky. Now, every 24 hours, the
signal level averages are reset to their current average and
That IS interesting.. It reads to me that the advice is to keep a "moving 300
pt ADEV" when continously monitoring a (pair of) frequency source in e.g a VLBI
site - the reason for limiting it to 300 pts being that much more than that is
likely to average out potential issues..
Does that make s
Hi
That’s the way I read what they are saying. More or less: Keep the number of
samples above
100, but below 300.
Bob
> On Jan 13, 2017, at 12:30 PM, Ole Petter Rønningen
> wrote:
>
> That IS interesting.. It reads to me that the advice is to keep a "moving 300
> pt ADEV" when continously
Mark, Ole,
Yes, averaging can both enhance precision but also destroy information. In many
cases too much data is a bad thing. The solution is to add another dimension to
the plot. Stable32 does this with DAVAR (dynamic Allan variance). TimeLab has a
multi- "trace" feature. Both of these break
On Fri, January 13, 2017 11:40 am, Bob Camp wrote:
> The ping response is anywhere from 2 ms out to 400 ms. Most of
> the time it's in the 3 to 9 ms range. Simply taking that
> down to < 1 us would be a really big deal.
I doubt that the response time will get that low, rather the time sync
will be
Hi
I’m sure you are right about the response time. Right now the variation is
running almost 3 ms
at one sigma on a ping so there is a lot to do simply to get the accuracy
anywhere near 1 us.
Bob
> On Jan 13, 2017, at 2:35 PM, Chris Caudle wrote:
>
> On Fri, January 13, 2017 11:40 am, Bob Ca
Can we please stop talking about pings?
Bob Camp wrote on Fri, 13 Jan 2017
at 15:12:38 -0500 in :
> I’m sure you are right about the response time. Right now the
> variation is running almost 3 ms at one sigma on a ping so there is
> a lot to do simply to get the accuracy anywhere near 1 us.
Us
Even with the long and variable ping time, time sync can work. The reason
it can work is that time is not re-sync'd in one "ping" but time sync is an
on-going process that occurs over a period as long as hours.
Think about adjusting the rate of a clock by hand. The computer (NTP) can
(and does) u
Hi
What standard protocol would you recommend I run from the command line on my
computer
to get a quick estimate of the timing lag and variablilty on my particular
WiFi connection?
Bob
> On Jan 13, 2017, at 3:25 PM, John Hawkinson wrote:
>
> Can we please stop talking about pings?
>
> Bob
Short answer: See man page for ntpq
Longer...
First run NTP then after some time (15 minute to an hour) at the command
line time type "ntpq -p"
"ntpq" will query NTP for timing statistics. It will report the average
delay between the local computer and the set of reference clocks (other
server
Hi
That *assumes* that NTP is installed on the laptop.
Bob
> On Jan 13, 2017, at 3:45 PM, Chris Albertson
> wrote:
>
> Short answer: See man page for ntpq
>
> Longer...
>
> First run NTP then after some time (15 minute to an hour) at the command
> line time type "ntpq -p"
>
> "ntpq" will
Hi
Ok. so I bring up NTP on the laptop against a server on the other side of the
country and install
NTP on the laptop. I get all of the jitter and offset of my cable modem plus
the network
issues between here and who know where. If I want to know the specific delay
issues just
on the WiFi con
Bob Camp wrote on Fri, 13 Jan 2017
at 15:35:19 -0500 in :
> What standard protocol would you recommend I run from the command
> line on my computer to get a quick estimate of the timing lag and
> variablilty on my particular WiFi connection?
Bob: I hope you read the whole of my message, rather t
To add to this I'd be curious in knowing about easy PC based ways to measure
network latencies / delays with microsecond accuracy vs millisecond accuracy.
The tools I used to use at work were generally designed for use on networks
where millisecond resolution measurements made sense as a "figure
Hi
It just so happens that I’m trying to track down an issue with my WiFi as
I type this. My *guess* is that there is a dropout going on. The only easy
way I can see to get a round trip time with a high data rate is to run ping.
It’s the only tool that gives me something that is fast enough to sp
It’s a little more complicated than that. A switch’s main cpu is like a host
with rx coalesce set to 100. And there are a surprising number of things that
trigger the main cpu beyond management functions. Multicast is a good example.
The amount of load on the main cpu can be quite variable, and
I think their advice was to limit the ADEV calculation for some tau to 300
bins. The standard error on estimating the standard deviation is ~ +- 5%
for 200 samples. So loosely speaking in the neighborhood of 100-300 bins
the resulting adev will have an rms uncertainty of roughly 5%. So limiting
the
On Fri, January 13, 2017 3:17 pm, Bob Camp wrote:
> It just so happens that I'm trying to track down an issue with my WiFi
> as I type this.
This is getting off topic for time-nuts very quickly, but use bufferbloat
and "make wifi fast" as search phrases. The guy who did a lot of the work
on queue
Hydrogen maser in radio astronomy to sync worldwide systems:
http://flip.it/rmbdRQ
(Lifted from the Albany, NY astronomy group).
--
Gary Woods O- K2AHC Public keys at home.earthlink.net/~garygarlic, or get
0x1D64A93D via keyserver
fingerprint = E2 6F 50 93 7B C7 F3 CA 1F 8B 3C C0 B0 28 6
An entire room kept near to absolute zero with a simple door access???Unlikely,
likely the writer is unfamiliar with science/engineering.
Bruce
On Saturday, 14 January 2017 11:39 AM, Gary Woods
wrote:
Hydrogen maser in radio astronomy to sync worldwide systems:
http://flip.it/rmbdRQ
On 1/13/17 2:19 PM, Chris Caudle wrote:
On Fri, January 13, 2017 3:17 pm, Bob Camp wrote:
It just so happens that I'm trying to track down an issue with my WiFi
as I type this.
This is getting off topic for time-nuts very quickly,
well, wireless distribution of accurate time is, I think, on
> What standard protocol would you recommend I run from the command line on my
> computer to get a quick estimate of the timing lag and variablilty on my
> particular WiFi connection?
I'd use ping. But you said "quick estimate".
My wifi is crappy enough that its noise swamps everything else.
On Fri, Jan 13, 2017 at 3:35 PM, Bob Camp wrote:
> Hi
>
> What standard protocol would you recommend I run from the command line on
> my computer
> to get a quick estimate of the timing lag and variablilty on my
> particular WiFi connection?
If I wanted to do this I would use MTR (it has been
On Fri, Jan 13, 2017 at 8:45 PM, Chris Albertson
wrote:
> Short answer: See man page for ntpq
>
> Longer...
>
> First run NTP then after some time (15 minute to an hour) at the command
> line time type "ntpq -p"
>
> "ntpq" will query NTP for timing statistics. It will report the average
> delay
On Fri, Jan 13, 2017 at 1:11 PM, Bob Camp wrote:
> Hi
>
> Ok. so I bring up NTP on the laptop against a server on the other side of
> the country and install
> NTP on the laptop. I get all of the jitter and offset of my cable modem
> plus the network
> issues between here and who know where. If I
If there is a modern microwave oven with a switching power supply,
or a cordless telephone around, you might want to look there.
The old linear supply ovens were easy to deal with because they
presented a strong CW signal that drifted around as voltage, load,
and temperature changed. The switcher
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