[time-nuts] Leap second smear at Google

[Christopher Quarksnow]

Besides the famous Android stint described in Google bug 5485
https://code.google.com/p/android/issues/detail?id=5485 that took 2 years
to fix, so many Android phones system clocks were 15 seconds fast then, I
just found the source of another discrepancy where Google spreads the leap
second offset to avoid artifacts with servers, platforms, environments or
programs unable to handle a sudden second leap :
http://googleblog.blogspot.com/2011/09/time-technology-and-leaping-seconds.html

Maybe not as bad as Oracle in 2009 :
http://www.pcworld.com/article/156453/article.html

I don't know how "elegant" this solution from Google is, especially with
Google Wallet time payments or transactions that could be back-dated in
relation to a banking system, or other Google apps, but I thought it might
be of interest to some before they need a house of clocks to keep in sync
with Google on such days ! http://www.youtube.com/watch?v=xyRKQ84ztkE

Christopher Quarksnow
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Re: [time-nuts] NITZ Timestamps

[Christopher Quarksnow]

Maybe the 15 second offset was to compensate for the old Android bug that
derived time from GPS rather than UTC ; Sprint told me at that time they
drove most towers with Stratum 2 ref. and only my Android phones exhibited
the issue. The other ones were no more than 0.1 sec off.


On Wed, Aug 21, 2013 at 6:59 PM, Tom Harris  wrote:

> Here's a general question about the NITZ timestamp that is sent by the
> phone tower when your mobile connects to it. Why are they so far off from
> the actual time? I have seen offsets up to 15 seconds behind, mind you this
> was from a tower in the bush, city towers are usually only 2 secs behind.
>
> Tom Harris 
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Re: [time-nuts] Checking Time difference between PCs

[Christopher Quarksnow]

About using w32tm /stripchart and the µs resolution :
Despite RFC 1305 compliant, Microsoft w32tm is still bound to the clock
interrupt frequency fed to the processor :
http://serverfault.com/questions/488983/is-it-viable-to-use-w32tm-stripchart-to-judge-time-variance-of-two-windows-host
So if you have a Cs clock as a reference in your computer, or maybe a
PTP-based external reference, you might not benefit from the µs
resolution

Chris


On Fri, May 24, 2013 at 3:39 AM, Bill Hawkins  wrote:

> Dear me!
>
> Your clock is off by four years and change!
>
> Bill Hawkins!
>
>
> -Original Message-
> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
> Behalf Of Christopher Quarksnow
> Sent: Thursday, May 23, 2013 9:06 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Checking Time difference between PCs
>
> This might do, even though I doubt the routines are using rdtsc to
> interpolate nondeterministic offset of the PIC architecture.
>
> w32tm /stripchart /computer: [/period:] [/dataonly]
> [/samples:]
>
> The current time is 3/8/2009 21:05:30 (local time).21:05:30
> d:+00.000s o:+00.3047845s
>
> Cheers,
>
> Chris
>
>
> On Thu, May 23, 2013 at 5:26 PM, Rex Moncur 
> wrote:
>
> > I wonder if anyone has suggestions as to how to check the timing
> variations
> > between two PCs that are running windows.
> >
> > The background to this request is that I am running two instances of
> the
> > Weak Signal Program WSJT on the same computer and get variations of
> +/-0.2
> > seconds.  It has been suggested that the variations might be caused by
> the
> > windows operating system.  As a check on this I am proposing to run
> two PCs
> > locked by GPS-18 USB and set by NMEATime which should show the
> difference
> > on
> > WSJT.  But is there some program that will show the difference due to
> the
> > PC
> > clocks alone? Or perhaps a program that outputs the PC time as a pulse
> on a
> > sound card so I can compare these on a CRO.
> >
> > Regards Rex VK7MO
> >
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Re: [time-nuts] Checking Time difference between PCs

[Christopher Quarksnow]

It was just a sample to show the precision.

On Fri, May 24, 2013 at 3:39 AM, Bill Hawkins  wrote:

> Dear me!
>
> Your clock is off by four years and change!
>
> Bill Hawkins!
>
>
> -Original Message-
> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
> Behalf Of Christopher Quarksnow
> Sent: Thursday, May 23, 2013 9:06 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Checking Time difference between PCs
>
> This might do, even though I doubt the routines are using rdtsc to
> interpolate nondeterministic offset of the PIC architecture.
>
> w32tm /stripchart /computer: [/period:] [/dataonly]
> [/samples:]
>
> The current time is 3/8/2009 21:05:30 (local time).21:05:30
> d:+00.000s o:+00.3047845s
>
> Cheers,
>
> Chris
>
>
> On Thu, May 23, 2013 at 5:26 PM, Rex Moncur 
> wrote:
>
> > I wonder if anyone has suggestions as to how to check the timing
> variations
> > between two PCs that are running windows.
> >
> > The background to this request is that I am running two instances of
> the
> > Weak Signal Program WSJT on the same computer and get variations of
> +/-0.2
> > seconds.  It has been suggested that the variations might be caused by
> the
> > windows operating system.  As a check on this I am proposing to run
> two PCs
> > locked by GPS-18 USB and set by NMEATime which should show the
> difference
> > on
> > WSJT.  But is there some program that will show the difference due to
> the
> > PC
> > clocks alone? Or perhaps a program that outputs the PC time as a pulse
> on a
> > sound card so I can compare these on a CRO.
> >
> > Regards Rex VK7MO
> >
> > ___
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> > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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> >
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Re: [time-nuts] Checking Time difference between PCs

[Christopher Quarksnow]

This might do, even though I doubt the routines are using rdtsc to
interpolate nondeterministic offset of the PIC architecture.

w32tm /stripchart /computer: [/period:] [/dataonly]
[/samples:]

The current time is 3/8/2009 21:05:30 (local time).21:05:30
d:+00.000s o:+00.3047845s

Cheers,

Chris


On Thu, May 23, 2013 at 5:26 PM, Rex Moncur  wrote:

> I wonder if anyone has suggestions as to how to check the timing variations
> between two PCs that are running windows.
>
> The background to this request is that I am running two instances of the
> Weak Signal Program WSJT on the same computer and get variations of +/-0.2
> seconds.  It has been suggested that the variations might be caused by the
> windows operating system.  As a check on this I am proposing to run two PCs
> locked by GPS-18 USB and set by NMEATime which should show the difference
> on
> WSJT.  But is there some program that will show the difference due to the
> PC
> clocks alone? Or perhaps a program that outputs the PC time as a pulse on a
> sound card so I can compare these on a CRO.
>
> Regards Rex VK7MO
>
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Re: [time-nuts] OT: eBay Contact Congress

[Christopher Quarksnow]

Just check the mail header (viewing message source in your mail client) and
look for the originating ip address.
Then go to arin.net and see if e-bay owns that block ; if the ip address is
from Nigeria, arin will refer you to Afrinic, or whatever RIR it's under.

Hope this helps,

Chris


On Mon, Apr 22, 2013 at 2:41 PM, Donald Henderickx
wrote:

> On 4/22/2013 12:21 PM, Max Robinson wrote:
>
>> I received one but I don't know if it's legit.
>>
>> Regards.
>>
>> Max.  K 4 O DS.
>>
>> Email: m...@maxsmusicplace.com
>>
>> Transistor site 
>> http://www.funwithtransistors.**net
>> Vacuum tube site: http://www.funwithtubes.net
>> Woodworking site http://www.angelfire.com/**electronic/funwithtubes/**
>> Woodworking/wwindex.html
>> Music site: http://www.maxsmusicplace.com
>>
>> To subscribe to the fun with transistors group send an email to.
>> funwithtransistors-subscribe@**yahoogroups.com
>>
>> To subscribe to the fun with tubes group send an email to,
>> funwithtubes-subscribe@**yahoogroups.com
>>
>> To subscribe to the fun with wood group send a blank email to
>> funwithwood-subscribe@**yahoogroups.com
>>
>> - Original Message - From: "J. Forster" 
>> To: 
>> Cc: 
>> Sent: Monday, April 22, 2013 8:13 AM
>> Subject: [time-nuts] OT: eBay Contact Congress
>>
>>
>>  Hi,
>>>
>>> I recieved a very odd communication, apparently from eBay, this morning.
>>> It is a request to contact Congress about sales taxes on internet sales.
>>>
>>> It APPEARS to be genuine, but I'm unconvinced.
>>>
>>> Has anybody else received this email, and is it for real?
>>>
>>> Puzzled,
>>>
>>> -John
>>>
>>> 
>>>
>>> __**_
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>>>
>>
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>> mailman/listinfo/time-nuts
>> and follow the instructions there.
>>
>>  Go to eBay. go to my eBay. messages, log into your account.If the
> message in question is not there it did not come from eBay. (run away run
> away)
> __**_
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Re: [time-nuts] RE; New Wrist watch

[Christopher Quarksnow]

There are many Wave Ceptor LCD versions such as WVM120J-1 (about $27) or
WV59A-1AV (about $49) that might not have the spin issue.

Chris


On Sun, Sep 9, 2012 at 4:34 PM, Robert Darlington wrote:

> The waveceptor's are okay but I can't wear mine much because I tend to
> cross timezones a lot.  The hands only run in one direction so when
> going to the west, it has to spin 11 hours forward.  This takes 20
> minutes.   I guess it's one way to kill time on an airplane.
>
> -Bob
>
> On Sun, Sep 9, 2012 at 1:12 PM, Rich and Marcia Putz 
> wrote:
> > I have a $49 Casio Wave Ceptor, white face black numerals, analog hands
> including second hand, date, alarm and WWVB syncing in the middle of the
> night. Only had to replace the battery once and it ticks are closer than I
> can discern when comparing to WWV @ 10or 15 Mhz.
> >
> > Rich, W9ENG
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Re: [time-nuts] 15 Seconds error...??

[Christopher Quarksnow]

GPS was incepted in 1982, at which point it was equal to UTC ; since then,
15 leap seconds were introduced to UTC, thus the 15-second offset and by
next July 1st, it will be 16 seconds.
The most common use of GPS time (hybrid?) is the Android system time, even
though Samsung Android phones use UTC discipline, possibly not thinking
like Google that GPS time is so prevalent

Christopher

On Mon, Jan 16, 2012 at 19:25, Brian, WA1ZMS  wrote:

> GPS has its own time scale.  Part of the GPS data stream contains the
> number
> of seconds that GPS and UTC differ by.
>
>
> -Brian, WA1ZMS
>
>
> -Original Message-
> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
> Behalf Of Dan Rae
> Sent: Monday, January 16, 2012 7:21 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] 15 Seconds error...??
>
> GPS time v. UTC ?
>
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Re: [time-nuts] US New Year countdown - accurate?

[Christopher Quarksnow]

It was accurate. I was right there using Android UTC time application.
Also about the leap-second on July 1st, this will allow revealing whether
Samsung just did a 15-second offset hack to get around Google bug 5485
(that makes non-Samsung Android phones currently 15 seconds fast), or if
really they tweaked firmware to derive utc-disciplined data rather than
gps.

Cheers,

Chris

On Sun, Jan 1, 2012 at 20:46, Jim Palfreyman  wrote:

> Hi folks,
>
> Ignoring the travesty of a lyric change on John Lennon's classic song, did
> anyone check to see if the clock countdown in Times Square was actually
> accurate?
>
> In times gone past countdowns have been notoriously off (worst I saw was a
> tv personality using his own watch and it was 25 seconds out).
>
> Oh and why we're at it here is my worst time-nut story...
>
> Pulled up in a "Loading Zone 8-6pm" at 18:00:10. Got out, came back 4
> minutes later to find a parking officer giving me a ticket.
>
> Me: "Look at the time (showing my watch) - it's 6:04"
>
> Him: "Not by my watch" (which said 5:59 at that point).
>
> Me (massive sarcasm voice): "So. Let me get this straight. Despite
> worldwide time standards keeping clocks accurate to billionths of a second
> and costing millions of dollars, all that is now been binned and we now
> keep world official time by your watch. Is that right?".
>
> Him: "Bu..."
>
> Me (interrupting and pulling out mobile): "Let's listen to the national
> time standard shall we?" (I dial and put on speaker - his watch is a good
> solid 5 minutes slow).
>
> Him: Walks off screwing up ticket.
>
> The sheer arrogance of the "Not by my watch" comment irks me to this day.
>
> Jim
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[time-nuts] Looking for 8-digit LED clock

[Christopher Quarksnow]

Wondering whether anyone would know of an off-the-shelf (even used) LED
clock with 1/100th of seconds and switchable to 24H mode (e.g going up to
23:59:59.99)
The closest I found was at Pylones a director's clock, yet the last 2 digits
were for frames, going from 0 to 23 and now they made a smaller one that's 7
digits with 1/10 seconds only.
Thanks !
Christopher
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Re: [time-nuts] Google NTP Servers and smearing leap seconds...

[Christopher Quarksnow]

It's interesting to see the title "*Why time matters at Google*" in the blog
when Androis bug 5485 has not been fixed in over two years, and most
Android-based phones are 15 seconds fast, as GPS-disciplined rather than
UTC. It appears only Samsung got around
When hearing about this, Daniel Gambis at IERS told me that there was such
as strong momentum to drop leap seconds (ITU, etc...), yet the "damage" is
done !

On Thu, Sep 15, 2011 at 16:34, Doug Calvert wrote:

> Time Technology and leaping seconds
>
>
> http://googleblog.blogspot.com/2011/09/time-technology-and-leaping-seconds.html
>
> "The solution we came up with came to be known as the “leap smear.” We
> modified our internal NTP servers to gradually add a couple of
> milliseconds to every update, varying over a time window before the
> moment when the leap second actually happens. This meant that when it
> became time to add an extra second at midnight, our clocks had already
> taken this into account, by skewing the time over the course of the
> day. All of our servers were then able to continue as normal with the
> new year, blissfully unaware that a leap second had just occurred. We
> plan to use this “leap smear” technique again in the future, when new
> leap seconds are announced by the IERS."
>
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Re: [time-nuts] What is NIST "official time" ?

[Christopher Quarksnow]

Actually I was in Seattle yesterday looking at a SkyScan "atomic" clock, and
it agreed with NIST time.gov applet, yet I was thrown off by some
Android-based applications such as Sidereal or TAI Clock and Converter, that
display "UTC", whereas it is apparently Android system time.
Whereas Android system time has been GPS-disciplined for about two years
(bug 5485), very few "smart" phones overcame the issue. Also most Android
ntp-based applications that I used until recently under Android 2.2 did not
work with 2.3 and that's the reason I used Sidereal or TAI Clock and
Converter. I finally resorted to UTC time, that truly retrieves UTC via ntp,
and now back in NY last night, all seems fine, except that Google, OHA and
other parties involved (who were informed of the Android bug way back)
should make sure that no one displays "UTC" in any Market application unless
it's derived from a relevant source.
It's dangerous enough that a good portion of Android phones are 15 seconds
fast, even though a carrier like Sprint is sending a pretty accurate UTC
stream even to basic phones.

Thanks to all,

Christopher

On Thu, Aug 4, 2011 at 12:02, Chris Albertson wrote:

> On Thu, Aug 4, 2011 at 7:16 AM, Christopher Quarksnow
>  wrote:
> > Wondering whether anyone can clarify what discipline the Boulder, CO NIST
> > facility is broadcasting (or showing on time.gov) and qualified as "The
> > official U.S. time".
> > It appears to be about 20 seconds slower than UTC
>
> I think something must be wrong with the way you are measuring.
> Propagation can't time add 20 seconds  Can you explain exactly what
> how you are measuring.
>
> Chris Albertson
> Redondo Beach, California
>
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>

  I was actually in Seattle looking at a SkyScan clock that concurred with
NIST and now back in New York today, seems I had an issue with Android
Sidereal software that claimed UTC, yet derived such UTC value from Android
system clock. Whereas I thought that the Android system clock was right
(namely Android bug 5485 was offset in the phone I was using), it actually
was not. I have alerted the author of sidereal software.
There seem to be a transition issue
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[time-nuts] What is NIST "official time" ?

[Christopher Quarksnow]

Wondering whether anyone can clarify what discipline the Boulder, CO NIST
facility is broadcasting (or showing on time.gov) and qualified as "The
official U.S. time".
It appears to be about 20 seconds slower than UTC and I could not find the
relation to other known time scales such as TAI, UTC, ET, UT1, GPS or
possibly grid or broadcast-interconnected reference.

Thanks !
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[time-nuts] NIST "official time"

[Christopher Quarksnow]

Wondering whether anyone can clarify what discpline the Boulder, CO facility
is broadcasting...
It appears to be about 20 seconds slower than UTC and I could not find the
relation to other known time scales like TAI, UTC, ET, UT1, GPS or possibly
grid or broadcast-interconnected reference.
Thanks !
On Aug 3, 2011 8:33 AM, "Francis Grosz"  wrote:
>
> Hi, Scott,
>
> They track because most of Arkansas is part of the Eastern
Interconnection and the transmission systems are tied together through that.
 The general shape follows the loading of the system; that is, as the load
increases throughout the day the alternators slip behind; as it decreases
they advance.  They try to keep the system frequency accurate to +/- 0.02
Hz. but that integrates out to a worst case of 72 cycles slip or
advance/hour.  PNNL has developed the Grid Friendly Grid Monitor software
and you can use that to watch the frequency and accumulated phase error of
the Western Interconnection.
>
> Here in New Orleans a friend in the power company who was interested
in its history told me a story.  In the very early days, frequency control
was pretty poor and it was hard to keep up with the changing load. So by 5
PM every day, every electric clock in the city was 10 or 15 minutes slow.
 So overnight they'd speed up the system and so by 8 AM the next morning
every electric clock would be 10 or 15 minutes fast because the total slip
during the day was 20 or 30 minutes.  Today we'd consider that absolutely
unacceptable (even for non-Time Nuts), but back then it just was.
>
> Still, elimination of TEC is idiotic.  I had occasion recently to talk
to a couple of very high-level power systems people and they thought it was
crazy as well.  Like elimination of leap seconds, we'll just have to see.
>
>  Francis
>
>
> >Message: 7
> >Date: Tue, 02 Aug 2011 21:18:17 -0500
> >From: Scott Newell 
> >To: time-nuts@febo.com
> >Subject: [time-nuts] Weird TEC data
> >Message-ID: <848527.81129...@smtp109.prem.mail.sp1.yahoo.com>
> >Content-Type: text/plain; charset="us-ascii"; format=flowed
> >
> >Here's the latest plot from my TEC test rigs.  Y-axis is phase error
> >(in 60 Hz cycles), X-axis is time in MJD.  The plot starts at 7AM local
time.
> >
> >http://n5tnl.com/tec/tec_test_01.png
> >
> >Same serial connected embedded hardware, timestamped on the receipt
> >of first character.  One machine (red line) is a Sun running debian,
> >the other (green line) is a Dell PC, also running debian.  Both
> >running ntp, of course.  One is located in a fairly large city (by
> >Arkansas standards!), the other is out in a small country
> >town.  Different utility providers.
> >
> >The general shape and bumps in the plots track nicely, but I'm
> >wondering why there's so many cycles difference after 36 hours.
> >
> >Comments?
>
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Re: [time-nuts] My Custom GPS clock

[Christopher Quarksnow]

Hello, Bert -

 Not having that much experience, I am wondering whether I could retrofit
their DE-DP22811 http://www.sureelectronics.net/goods.php?id=1164 to make an
8 digits clock having 1/100s:
 23 59 59 99
Based in NYC and ideally I would feed it UTC reference, either by GPS minus
15 seconds (as leap seconds are likely to be dropped) or any other source. I
only need 1/100 s accuracy, might even drive from power line.
I'd be glad to pay someone to implement. I have Paypal. The closest thing I
found was a director's clock, yet frames from 0 to 24 instead of hundreds of
seconds from 0 to 99.

Thanks,
Christopher



On Fri, Jul 22, 2011 at 16:53, Bert, VE2ZAZ  wrote:

> Hi Brooke,
>
> I go by memory here, but I believe it is a pair of DE-DP13112 (P4 32X8 3208
> Red LED Dot Matrix Unit Board SPI Like), which are currently on sale for $11
> ea. I bought mine on eBay.
>
> Cheers,
>
> Bert, VE2ZAZ
>
>
>
>
> >
> >From: Brooke Clarke 
> >To: "Bert, VE2ZAZ" ; Discussion of precise time and
> frequency measurement 
> >Sent: Friday, July 22, 2011 4:36:33 PM
> >Subject: Re: [time-nuts] My Custom GPS clock
>  >
> >Hi Bert:
> >
> >Which Sure Electronics display board did you use (they make a bunch of
> >different ones)?
> >http://www.sureelectronics.net/category.php?id=60
> >
> >Have Fun,
> >
> >Brooke Clarke
> >http://www.PRC68.com 
> >http://www.End2PartyGovernment.com/ 
> >
> >
> >Bert, VE2ZAZ wrote:
> >> Hello Everyone,
> >>
> >> I thought some of you might be interested in the following. A few months
> ago, a few time-nuts discussed what they had done to convert existing
> equipment to a large GPS clock. I elected to design my own clock display
> instead. Mine is fed by a Garmin GPS-35 GPS and it uses a 64 x 8 LED array
> for the display. It is driven by a PIC18F1220 with custom firmware.
> >>
> >>
> >> I have posted a Youtube video that shows the unit in action:
> http://www.youtube.com/watch?v=RJE-PeUtxfU
> >> The unit is described in more detail on my website at:
> http://ve2zaz.net/GPS_Clock/GPS_Clock.htm
> >>
> >> Cheers,
> >>
> >> Bert, VE2ZAZ
> >> ___
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> >>
> >>
> >>
> >
> >
> >
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[time-nuts] ARe: 60Hz zero-crossingAa

[Christopher Quarksnow]

QAAAaQpaPA
On Jun 29, 2011 7:17 PM, "Pete Lancashire"  wrote:
> Someone mentioned a modern chip for detecting zero crossing.
>
> I seem to have deleted it
>
> Anyone have it ?
>
> -pete
>
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Re: [time-nuts] usb serial converter

[Christopher Quarksnow]

Just to set the record straight about DOS not supporting USB :
http://bretjohnson.us/

Christopher

On Tue, Jun 14, 2011 at 20:25,  wrote:

> Just a side note here should it ever come up, those usb serial converters
> don't work in DOS. DOS doesn't support USB. You can kind of get them working
> in the so-called DOS window of 32 bit windows, but many DOS apps won't work
> because DOS allowed from direct control of the port and windows gets in the
> way.
>
> For a while, I was getting away with a Socketcom pcmcia serial port and
> open DOS (or maybe Free DOS, I forget. My next notebook had cardbus which I
> guess needs a 32 bit driver.
>
> Over the years I have picked up various Socketcom serial cards at flea
> markets or surplus shops should anyone wish to know what operating systems
> support them. I also have the DOS TSRs to run the cards. Socketcom never had
> them on their website, so I had to buy a used card on ebay to get the
> software.
>
> One of the annoying things is Dell provides a hardware serial port if you
> buy a docking station, but no way to just get a serial port by itself using
> the docking port. Well at least that I know of.
>
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Re: [time-nuts] GPS interference and history...

[Christopher Quarksnow]

Also given that Galileo is subtantially delayed due to European budget
constraints
http://www.engadget.com/2010/10/07/eus-galileo-satnav-system-orbiting-way-past-budget-delayed-unt/
it does not seem like it can be expected to mitigate the issue for
navigation purpose, aside political implications and the fact that every
aircraft might not have combined receivers.
Chris
On Fri, Jun 10, 2011 at 12:42, Bob Camp  wrote:

> Hi
>
> The FCC (like most US agencies) has a mission to promote as well as
> regulate. The promotion side is what drives them to allocate frequencies in
> a way that you can reasonably produce gear. They have always come back
> years
> later and tried to change things around. Every time, the same issues get
> hashed over. Sometimes a change actually gets made, sometimes not.
>
> What's surprising with the GPS impact here is that the usual conversations
> are taking place a bit late in the process. The impact on legacy timing
> gear
> is one part of a much larger issue here. Hopefully it does not get lost in
> the back and forth. There's an enormous amount of gear out there that gets
> timing off of GPS.
>
> Bob
>
> -Original Message-
> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
> Behalf Of William H. Fite
> Sent: Friday, June 10, 2011 9:47 AM
> To: shali...@gmail.com; Discussion of precise time and frequency
> measurement
>  Subject: Re: [time-nuts] GPS interference and history...
>
> You folks are all far more knowledgeable than I on these issues so I have a
> question:
>
> To what extent, from both an engineering perspective and from the
> standpoint
> of public policy, should it be the obligation of transmitter and receiver
> manufacturers to design and build devices with sufficient filtering, et
> alia, to avoid or at least vastly minimize problems such as those described
> below by Didier?
>
> I suppose from an engineering standpoint the issue is one of do-ability and
> from the public policy perspective, how much it is reasonable to expect
> both
> those who transmit and those who receive to pay for equipment that will
> minimize interference problems, given that we are running out of spectrum
> and demands for chunks of it will continue to pour in.
>
> Both technical information and philosophical ramblings will be appreciated.
>
> Bill
>
> On Fri, Jun 10, 2011 at 9:16 AM,  wrote:
>
> > The problem is that many FM receivers leak LO signal, so if 2 receivers
> are
> > next to each others and set 10.7 MHz apart, one will be receiving the LO
> of
> > the oter.
> >
> > Didier KO4BB
> >
> > Sent from my BlackBerry Wireless thingy while I do other things...
> >
> > -Original Message-
> > From: Chuck Forsberg WA7KGX N2469R 
> > Sender: time-nuts-boun...@febo.com
> > Date: Thu, 09 Jun 2011 12:16:48
> > To: ; Discussion of precise time and frequency
> > measurement
> > Reply-To: Discussion of precise time and frequency measurement
> >
> > Subject: Re: [time-nuts] GPS interference and history...
> >
> >  The image frequency for an FM receiver with a 10.7 mHz IF
> > is 21.4 mHz above or below.  Perhaps they were worried about
> > receivers with IFs in the 5 mHz range?
> >
> > --
> > Chuck Forsberg WA7KGX N2469R c...@omen.com   www.omen.com
> > Developer of Industrial ZMODEM(Tm) for Embedded Applications
> >   Omen Technology Inc  "The High Reliability Software"
> > 10255 NW Old Cornelius Pass Portland OR 97231   503-614-0430
> >
> >
> > ___
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Re: [time-nuts] IEEE Spectrum Magazine interviews one of our own...

[Christopher Quarksnow]

About Steven Cherry, here is a famous example of system outage due to leap
seconds :
http://www.dba-oracle.com/oracle_news/news_leap_second_causing_new_years_rac_node_crashes.htm

Also Google Android is plagued with an issue visible on phones like the
Motorola Droid or HTC EVO 4G, where the time displayed is GPS instead of
UTC, as possibly someone did not know of leap seconds :
http://code.google.com/p/android/issues/detail?id=5485

Concerning leap seconds, I spoke to Dr Daniel Gambis last month (he is the
one who decides to insert them), and he suggested that despite astronomers
having to incur costly retooling, it seems to him that ITU under U.S.
pressure might do away with leap seconds soon. He pointed me to the
following article :
www.agi.com/downloads/resources/user-resources/downloads/whitepapers/DebateOverUTCandLeapSeconds.pdf

As far as leap years every 4 years, that does not apply to multiples of 400
like year 2000.

Just my 2¢

Christopher Quarksnow



On Wed, May 25, 2011 at 02:30, cook michael  wrote:

> Le 25/05/2011 04:00, Tom Holmes a écrit :
>
> 
> Steven Cherry is exaggerating when he says " most systems go down for
> planned maintenance instead of trying to deal with leap seconds in real
> time."
>  As someone who has been supporting major industrial, banking, airline
> systems for the last 30 years, I remember NO down time, or outage due to
> leap second insertion. In fact, I don't know of any  commercial
> applications, that care about it. Most systems administrators that I had
> contact with didn't know that th leap seconds existed, and did not
> configure, check or update their ntp servers  to enable them to be taken
> into account.  There were of course outages and errors due to clock updates,
> but they were all attributable to operators trying to change the clocks by
> large increments manualy or bad ntp configurations, such as allowing large
> step changes instead of slewing .  We have up till now been faced only with
> positive leap second insertion, but negative updates are also possible.
> Testing I have done on unix based operating systems show no adverse effects
> to negative leap second insertion either.
>
>
>
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