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radio time code clock error
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N_Cook
Jun 22, 2015, 2:40:55 AM6/22/15
to
Anyone any insight into this error? Yesterday , coincidently? the
longest day. Set the alarm function for 06:30. Luckily woke just after
06:00 and decided to get up . Synchronous mains clock read 06:08 but
radio-code clock read 04:08, minute and seconds agreeing with another
radio-code clock but it had decided to go east 2 time zones. Still like
that about 07:00 but on returning in the evening the erroneous clock had
reset itself. How to predict when this error will reoccur? any
amelioration, plenty of LCD contrast so presumably the batteries are ok?
longest day. Set the alarm function for 06:30. Luckily woke just after
06:00 and decided to get up . Synchronous mains clock read 06:08 but
radio-code clock read 04:08, minute and seconds agreeing with another
radio-code clock but it had decided to go east 2 time zones. Still like
that about 07:00 but on returning in the evening the erroneous clock had
reset itself. How to predict when this error will reoccur? any
amelioration, plenty of LCD contrast so presumably the batteries are ok?
Jeff Liebermann
Jun 22, 2015, 3:16:03 AM6/22/15
to
nuts from RF noise in the shop. They then reset themselves after
midnight, when 60 KHz propagation is best. In the UK, you're probably
using MSF.
<http://www.npl.co.uk/science-technology/time-frequency/products-and-services/time/msf-radio-time-signal>
They do have some scheduled outages, but that's not the problem this
time:
<http://www.npl.co.uk/science-technology/time-frequency/products-and-services/time/msf-outages>
Offhand, I would guess(tm) that your unspecified model radio clock has
a dying battery. My various clocks do some rather strange things when
the battery is low.
You might want to fasten your seat belt on June 30th.
<http://www.dailymail.co.uk/sciencetech/article-3131840/The-longest-day-Leap-second-make-61-second-minute-end-June-experts-warn-break-internet.html>
<http://www.wired.com/2015/01/leap-second-rattle-internet-theres-plot-kill/>
<http://money.cnn.com/2015/01/13/technology/leap-second/>
The good news is that you'll get an extra second of sleep during the
night of June 30th.
More:
<http://www.leapsecond.com/java/nixie.htm>
<http://802.11junk.com/jeffl/crud/GPS-vs-UTC.jpg>
At the tone, the time will be:
<http://www.leapsecond.com/java/gpsclock.htm>
Ummm... never mind.
--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
N_Cook
Jun 22, 2015, 4:41:32 AM6/22/15
to
compared it to , was fine . At least I now know not to rely on
"no-name" and use it in alarm mode with another alarm clock. If it went
erroneous "to the west" it would not be so problematic
Ralph Mowery
Jun 22, 2015, 10:00:14 AM6/22/15
to
"N_Cook" <div...@tcp.co.uk> wrote in message
news:mm8aj3$o5i$1...@dont-email.me...
to which time zone the clock is set for.
N_Cook
Jun 22, 2015, 11:17:40 AM6/22/15
to
LON for London as in the Casio. Automatically seems to selct UK , the
strongest signal? along with automatic daylight saving changes.
Just pressed reset to remind me that no country option comes up and
within 10 minutes had sync'd with the Casio , in effect.
Tried Google Images but this one not seen in the first 3 pages of pics
of silver desktop "radio controlled" LCD clocks
N_Cook
Jun 22, 2015, 11:25:07 AM6/22/15
to
So perhaps that was the failure mechanism. Rugby went down for
maintainence or its signal got locally shadowed/echoed/interferred with
and if Darmstadt was a stronger/clearer? signal , perhaps reset itself
to CET time for a while. The Casio having a preset station option , it
may loose updating but it would not try to find another code source.
maintainence or its signal got locally shadowed/echoed/interferred with
and if Darmstadt was a stronger/clearer? signal , perhaps reset itself
to CET time for a while. The Casio having a preset station option , it
may loose updating but it would not try to find another code source.
N_Cook
Jun 22, 2015, 11:35:28 AM6/22/15
to
a transmitter for the Cape Verde Islands.
malua mada!
Jun 22, 2015, 2:48:19 PM6/22/15
to
I have an Oregon Scientific alarm clock that has five prominent buttons on its face: Clock, UP, DOWN, ALARM, ZONE.
I have hit the zone button by mistake before.
It steps through the 4 US time zones.
I have hit the zone button by mistake before.
It steps through the 4 US time zones.
Bob F
Jun 22, 2015, 9:09:29 PM6/22/15
to
figured that it made a mistake interpreting the received signal, perhaps due to
interference. It has corrected by the next day each time.
N_Cook
Jun 23, 2015, 2:15:20 AM6/23/15
to
likely get local interference?
Looked inside and only identifying features are these overlay numbers on
the 2 boards
ykf14547 ad085220 ad085211
otherwise little more than 2 crystals and 2 black epoxy humps over RF
end and LCD handling SM chips
thekma...@gmail.com
Jun 23, 2015, 4:21:11 AM6/23/15
to
My "radio time code" system never fails: I have a shortwave
radio, tune in time signals at 5, 10, 15, or 20mHz, and set
all my clocks and watches at the beep.
Works like a charm!
radio, tune in time signals at 5, 10, 15, or 20mHz, and set
all my clocks and watches at the beep.
Works like a charm!
N_Cook
Jun 23, 2015, 4:39:48 AM6/23/15
to
transmission train?
I used to rely on the teletext time that came with the VITS of analogue
TV, but all gone belly-up with digital MUX. In the UK we have the
ridiculous business of the genuine radio pips relayed onto the "radio"
sections of MUX TV, can be up to 10 seconds out via the codec delays.
Ralph Mowery
Jun 23, 2015, 10:21:21 AM6/23/15
to
news:mmb5tv$9b6$1...@dont-email.me...
If using a short wave receiver the signal is being picked up direct from a
station in the US. The only delay is the time it takes for the signal to
get to you by radio which is around the earth about 7 times in one second
and the delay of the sound from the speaker to you rear.
Both are much faster than you cn hit a button on the clock to set the time.
station in the US. The only delay is the time it takes for the signal to
get to you by radio which is around the earth about 7 times in one second
and the delay of the sound from the speaker to you rear.
Both are much faster than you cn hit a button on the clock to set the time.
Jeroni Paul
Jun 27, 2015, 5:38:36 PM6/27/15
to
The oldest one is 13 years old and is an alarm clock I check daily, in these years I have had it three times take an incorrect time/date probably from interference. It either takes the right time or does not sync, three times in 13 years seems not bad for the simple parity bit protection the protocol uses.
I think, however, it is somewhat dangerous to have the clocks sync at night *after* you have checked they are set correctly, so if bad reception sets wrong data they will fail to wake you up at the right time.
thekma...@gmail.com
Jun 27, 2015, 10:26:03 PM6/27/15
to
Jeroni Paul wrote: "The oldest one is 13 years old and is an alarm clock I check daily,
I've got the best time sync source of all, courtesy
the NIST and WWVB! ;)
in these years I have had it three times take an incorrect time/date probably from
interference. It either takes the right time or does not sync, three times in 13 years seems
not bad for the simple parity bit protection the protocol uses.
I think, however, it is somewhat dangerous to have the clocks sync at night *after* you have
checked they are set correctly, so if bad reception sets wrong data they will fail to wake you
up at the right time. "
Enough reasons for me not to use the freakin' things...
interference. It either takes the right time or does not sync, three times in 13 years seems
not bad for the simple parity bit protection the protocol uses.
I think, however, it is somewhat dangerous to have the clocks sync at night *after* you have
checked they are set correctly, so if bad reception sets wrong data they will fail to wake you
up at the right time. "
I've got the best time sync source of all, courtesy
the NIST and WWVB! ;)
Jeff Liebermann
Jun 27, 2015, 10:56:15 PM6/27/15
to
On Sat, 27 Jun 2015 14:38:33 -0700 (PDT), Jeroni Paul
<JERON...@terra.es> wrote:
>I live in a fringe reception area for the german time
>signal at 77.5kHz
Spain? According the coverage map at:
<JERON...@terra.es> wrote:
>I live in a fringe reception area for the german time
>signal at 77.5kHz
<http://www.ptb.de/cms/en/ptb/fachabteilungen/abt4/fb-44/ag-442/dissemination-of-legal-time/dcf77/reach-of-dcf77.html>
Yes, the signal is probably not very strong and you're in the skywave
only region.
>and have many clocks that use this signal but because
>a marginal reception they do not always sync.
transmits a phase modulated signal,
<https://en.wikipedia.org/wiki/DCF77#Phase_modulation>
which works better for weak signal due to better processing gain. I'm
in the USA and have not tried it with over-the-air DCF77, but have
played with simulators and with WWVB, which also has a phase modulated
BPSK signal. The problem is that the technology seems to be patented
and chips are not forthcoming. Also, the addition of BPSK modulation
caused some old WWVB receiver chips to fail. No clue what the
situation was with DCF77 but it might be worth checking.
>The curious thing about this is every night I have a different set
>of clocks sync, they seem to decide at random when the signal was
>good enough.
take much computah or switcher noise to trash the signal, especially
when it's weak in the first place. If your devices have a loopstick
for an antenna, they are directional, with the strongest signal
perpendicular to the loopstick. I was having random updates until I
moved my WWVB clock away from several switching power supplies.
>The oldest one is 13 years old and is an alarm clock I check daily,
>in these years I have had it three times take an incorrect time/date
>probably from interference. It either takes the right time or does
>not sync, three times in 13 years seems not bad for the simple parity
>bit protection the protocol uses.
correct time be received successfully more than once before it will
sync. This is a function of the chip design.
>I think, however, it is somewhat dangerous to have the clocks sync
>at night *after* you have checked they are set correctly, so if
>bad reception sets wrong data they will fail to wake you up at
>the right time.
Propagation at VLF frequencies works best after midnight in the USA. I
think it's the same for a north-south path, but I'm not sure. Note
the increases in coverage area after midnight for WWVB:
<http://tf.nist.gov/stations/wwvbcoverage.htm>
<http://www.febo.com/time-freq/wwvb/sig-strength/>
I couldn't find something similar for DCF77.
Michael Black
Jun 27, 2015, 11:35:11 PM6/27/15
to
it was all ground-wave, and well penetrating.
If it was on shortwave, you would be stuck with a given frequency for a
givne time, which of course is why WWV transmits on a bunch of
frequencies.
The reason I've seen for late night sync'ing (and which makes sense) is
that in the wee hours of the morning, fewer people are up, thus much less
manmade interference. So the CFLs are turned off, the tv sets are turned
off (probably a bigger issue when they were actually CRTs, all that
horizontal sync frequencies into the deflection coil), lots of other
things that might be on in the daytime are off so they aren't making as
much noise.
I've noticed this. My Casio Waveceptor watch starts looking at midnight
local time, and if I have the CFL on at the time, it likely doesn't sync
up, but will at a later hour (the watch is better than most of the clocks,
since it tries multiple times). COnversely, if I have the CFL off, it
generally will sync at midnight.
And I'm probably at the far edge of the reliable reception area.
Of course, with at least some of the clocks, one does have the option of
pressing button (or putting the batteries back in) so the clock tries to
sync up, no matter what time it is.
Michael
N_Cook
Jun 28, 2015, 8:06:27 AM6/28/15
to
As an alarm clock, losing synch and drifting a second or two , to a
background quartz crystal clock, is no great problem
Jeff Liebermann
Jun 28, 2015, 1:13:37 PM6/28/15
to
On Sat, 27 Jun 2015 23:37:42 -0400, Michael Black <et...@ncf.ca>
wrote:
>I thought low frequencies were used by WWVB (and WWVL before it) because
>it was all ground-wave, and well penetrating.
The skywave doesn't magically go away at lower frequencies. For
example, here's a study on hearing both WWVB and JJY (Japan) in
Germany, which certainly would require skywave propagation.
<http://df6nm.bplaced.net/LF/MSFgaps/MSFgaps.htm>
See 3rd graph from the top. Unfortunately, I've never bothered to do
any DXing on VLF, but have been told that it's possible to hear Europe
and Japan in California if the conditions are right. VLF DX list:
<http://www.dxinfocentre.com/time-vlf.htm>
Unlike HF (high freq) propagation, which is "bent" by the ionosphere
back towards the ground, VLF frequencies are reflected off the D
layer.
<http://vlf.stanford.edu/research/introduction-vlf>
>If it was on shortwave, you would be stuck with a given frequency for a
>givne time, which of course is why WWV transmits on a bunch of
>frequencies.
Actually, VLF has the same problem. Beyond some distance (which
varies with antenna size and power level), the various time sync
stations become very sensitive to ionospheric layer conditions, which
is mostly controlled by the sun. During the day, skywave propagation
sucks, while ground wave is unaffected. However, when there's dark
over most of the distance between the transmitter and the receiver,
the skywave returns. More on how it works:
<http://solar-center.stanford.edu/SID/activities/ionosphere.html>
>The reason I've seen for late night sync'ing (and which makes sense) is
>that in the wee hours of the morning, fewer people are up, thus much less
>manmade interference.
That would be so nice if it were true, but it's not. It's not man
made interference that causes most reception problems, it's lightning
and atmospheric RF noise that are extremely high at VLF frequencies.
See the graph at:
<https://en.wikipedia.org/wiki/Atmospheric_noise>
<https://en.wikipedia.org/wiki/Atmospheric_noise#/media/File:Atmosphericnoise.PNG>
At 60 KHz, the noise level is about 80dB above the normal thermal
noise. When designing a receiver for 60 KHz, the problem is not the
usual NF (noise figure) and gain, but rather being able to remain
linear and handle the overload produced by the noise. That's why you
often see VLF receiver front ends with heat sinks on the RF
transistors.
Incidentally, the high noise levels is also why you can get away with
using tiny antennas with loss instead of gain. A bigger antenna will
amplify the noise and the signal equally which doesn't improve things.
A bigger antenna also produces more voltage at the receiver input,
which has to handled by an increasingly higher voltage and power input
stage. However, what a bigger antenna might do is increase the Q of
the antenna (i.e. decrease the antenna bandwidth) which would pickup
less off frequency noise, which will help increase the SNR (signal to
noise ratio).
>So the CFLs are turned off, the tv sets are turned
>off (probably a bigger issue when they were actually CRTs, all that
>horizontal sync frequencies into the deflection coil), lots of other
>things that might be on in the daytime are off so they aren't making as
>much noise.
Look again at the noise graph, and notice the red line added showing
man made noises. At 60 KHz, the man made noise is about equal to the
atmospheric noise.
If you want to pursue such a noise source survey, I suggest you build
a loop resonant at 60 KHz and plug into an oscilloscope looking for
noise. I suggest a very high Q magnetic loop so that it only picks up
noise very close to 60 KHz. Just about anything with a switching
power supply should show up as a noise source. I have some opinions
on CFL lamps, LED lamps, and plasma TVs which I'm not quite sure are
correct, so I'll not comment on those. Let's just say I have some
very quiet LED lamps and some VERY noisy LED lamps.
>I've noticed this. My Casio Waveceptor watch starts looking at midnight
>local time, and if I have the CFL on at the time, it likely doesn't sync
>up, but will at a later hour (the watch is better than most of the clocks,
>since it tries multiple times). COnversely, if I have the CFL off, it
>generally will sync at midnight.
That sounds about right. The chip, usually made by C-Max uses an
algorithm to determine when to listen. The problem is battery life.
It makes no sense to listen during daylight hours, so it doesn't. If
it sync at midnight, it doesn't try again later. If it fails, it
retries according to some pattern. I used to have the link to the
details, but can't find it right now. This is close but not the one I
was looking for:
<http://www.c-max-time.com/tech/software6005.php>
>And I'm probably at the far edge of the reliable reception area.
Probably true with a wristwatch receiver or consumer device. Not true
with a proper loop antenna, which gets much better range. In the
early 1980's, I setup a WWVB receiver in an area infested with high
electrical noise. None of the commodity WWVB clocks would work. A
shielded loop antenna and overkill coax shielding did the trick.
Something like this, except my loop was circular and about 1 meter
wide:
<http://www.ka7oei.com/wwvb_antenna.html>
>Of course, with at least some of the clocks, one does have the option of
>pressing button (or putting the batteries back in) so the clock tries to
>sync up, no matter what time it is.
I hacked one of clocks to do that so I could make measurements:
<http://802.11junk.com/jeffl/WWVB%20test/>
The receiver inside the antenna has an "enable" line to turn it on and
off. In this device, it's labeled PON. The clock/display/control
chip enables it according to the previously mentioned algorithm. I
tied the line high (after disconnecting it from the clock) so that it
would run continuously. It takes about 3 weeks to kill the two AAA
batteries when running continuously.
Clean signal that will decode correctly:
<http://802.11junk.com/jeffl/WWVB%20test/loopstick-perpendicular-to-WWVB.jpg>
Noisy signal that won't work:
<http://802.11junk.com/jeffl/WWVB%20test/end-pointed-at-WWVB.jpg>
<http://802.11junk.com/jeffl/WWVB%20test/loopstick-vertical.jpg>
wrote:
>I thought low frequencies were used by WWVB (and WWVL before it) because
>it was all ground-wave, and well penetrating.
example, here's a study on hearing both WWVB and JJY (Japan) in
Germany, which certainly would require skywave propagation.
<http://df6nm.bplaced.net/LF/MSFgaps/MSFgaps.htm>
See 3rd graph from the top. Unfortunately, I've never bothered to do
any DXing on VLF, but have been told that it's possible to hear Europe
and Japan in California if the conditions are right. VLF DX list:
<http://www.dxinfocentre.com/time-vlf.htm>
Unlike HF (high freq) propagation, which is "bent" by the ionosphere
back towards the ground, VLF frequencies are reflected off the D
layer.
<http://vlf.stanford.edu/research/introduction-vlf>
>If it was on shortwave, you would be stuck with a given frequency for a
>givne time, which of course is why WWV transmits on a bunch of
>frequencies.
varies with antenna size and power level), the various time sync
stations become very sensitive to ionospheric layer conditions, which
is mostly controlled by the sun. During the day, skywave propagation
sucks, while ground wave is unaffected. However, when there's dark
over most of the distance between the transmitter and the receiver,
the skywave returns. More on how it works:
<http://solar-center.stanford.edu/SID/activities/ionosphere.html>
>The reason I've seen for late night sync'ing (and which makes sense) is
>that in the wee hours of the morning, fewer people are up, thus much less
>manmade interference.
made interference that causes most reception problems, it's lightning
and atmospheric RF noise that are extremely high at VLF frequencies.
See the graph at:
<https://en.wikipedia.org/wiki/Atmospheric_noise>
<https://en.wikipedia.org/wiki/Atmospheric_noise#/media/File:Atmosphericnoise.PNG>
At 60 KHz, the noise level is about 80dB above the normal thermal
noise. When designing a receiver for 60 KHz, the problem is not the
usual NF (noise figure) and gain, but rather being able to remain
linear and handle the overload produced by the noise. That's why you
often see VLF receiver front ends with heat sinks on the RF
transistors.
Incidentally, the high noise levels is also why you can get away with
using tiny antennas with loss instead of gain. A bigger antenna will
amplify the noise and the signal equally which doesn't improve things.
A bigger antenna also produces more voltage at the receiver input,
which has to handled by an increasingly higher voltage and power input
stage. However, what a bigger antenna might do is increase the Q of
the antenna (i.e. decrease the antenna bandwidth) which would pickup
less off frequency noise, which will help increase the SNR (signal to
noise ratio).
>So the CFLs are turned off, the tv sets are turned
>off (probably a bigger issue when they were actually CRTs, all that
>horizontal sync frequencies into the deflection coil), lots of other
>things that might be on in the daytime are off so they aren't making as
>much noise.
man made noises. At 60 KHz, the man made noise is about equal to the
atmospheric noise.
If you want to pursue such a noise source survey, I suggest you build
a loop resonant at 60 KHz and plug into an oscilloscope looking for
noise. I suggest a very high Q magnetic loop so that it only picks up
noise very close to 60 KHz. Just about anything with a switching
power supply should show up as a noise source. I have some opinions
on CFL lamps, LED lamps, and plasma TVs which I'm not quite sure are
correct, so I'll not comment on those. Let's just say I have some
very quiet LED lamps and some VERY noisy LED lamps.
>I've noticed this. My Casio Waveceptor watch starts looking at midnight
>local time, and if I have the CFL on at the time, it likely doesn't sync
>up, but will at a later hour (the watch is better than most of the clocks,
>since it tries multiple times). COnversely, if I have the CFL off, it
>generally will sync at midnight.
algorithm to determine when to listen. The problem is battery life.
It makes no sense to listen during daylight hours, so it doesn't. If
it sync at midnight, it doesn't try again later. If it fails, it
retries according to some pattern. I used to have the link to the
details, but can't find it right now. This is close but not the one I
was looking for:
<http://www.c-max-time.com/tech/software6005.php>
>And I'm probably at the far edge of the reliable reception area.
with a proper loop antenna, which gets much better range. In the
early 1980's, I setup a WWVB receiver in an area infested with high
electrical noise. None of the commodity WWVB clocks would work. A
shielded loop antenna and overkill coax shielding did the trick.
Something like this, except my loop was circular and about 1 meter
wide:
<http://www.ka7oei.com/wwvb_antenna.html>
>Of course, with at least some of the clocks, one does have the option of
>pressing button (or putting the batteries back in) so the clock tries to
>sync up, no matter what time it is.
<http://802.11junk.com/jeffl/WWVB%20test/>
The receiver inside the antenna has an "enable" line to turn it on and
off. In this device, it's labeled PON. The clock/display/control
chip enables it according to the previously mentioned algorithm. I
tied the line high (after disconnecting it from the clock) so that it
would run continuously. It takes about 3 weeks to kill the two AAA
batteries when running continuously.
Clean signal that will decode correctly:
<http://802.11junk.com/jeffl/WWVB%20test/loopstick-perpendicular-to-WWVB.jpg>
Noisy signal that won't work:
<http://802.11junk.com/jeffl/WWVB%20test/end-pointed-at-WWVB.jpg>
<http://802.11junk.com/jeffl/WWVB%20test/loopstick-vertical.jpg>
Phil Hobbs
Jul 4, 2015, 1:10:25 PM7/4/15
to
the sky. ;)
Cheers
Phil Hobbs
(We just had a leap second.)
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics
160 North State Road #203
Briarcliff Manor NY 10510
hobbs at electrooptical dot net
http://electrooptical.net
Jeroni Paul
Jul 6, 2015, 3:03:17 PM7/6/15
to
Jeff Liebermann wrote:
> >I live in a fringe reception area for the german time
> >signal at 77.5kHz
>
> Spain? According the coverage map at:
> <http://www.ptb.de/cms/en/ptb/fachabteilungen/abt4/fb-44/ag-442/dissemination-of-legal-time/dcf77/reach-of-dcf77.html>
> Yes, the signal is probably not very strong and you're in the skywave
> only region.
Good observer, yes, Spain. Also the Pyrenees are in the way blocking most ground signal.
> >I live in a fringe reception area for the german time
> >signal at 77.5kHz
>
> Spain? According the coverage map at:
> <http://www.ptb.de/cms/en/ptb/fachabteilungen/abt4/fb-44/ag-442/dissemination-of-legal-time/dcf77/reach-of-dcf77.html>
> Yes, the signal is probably not very strong and you're in the skywave
> only region.
> >and have many clocks that use this signal but because
> >a marginal reception they do not always sync.
>
> That sounds like the older amplitude modulated system. DCF77 also
> transmits a phase modulated signal,
> <https://en.wikipedia.org/wiki/DCF77#Phase_modulation>
There is a long wave radio transmitter in France at 162 kHz that carries time information by phase modulation of its carrier:
https://en.wikipedia.org/wiki/Allouis_longwave_transmitter
I find it an efficient way to use existing resources, also you can check for reception by listening with a LW radio.
> >The curious thing about this is every night I have a different set
> >of clocks sync, they seem to decide at random when the signal was
> >good enough.
>
> Kinda sounds like you're getting some local interference. It doesn't
> take much computah or switcher noise to trash the signal, especially
> when it's weak in the first place. If your devices have a loopstick
> for an antenna, they are directional, with the strongest signal
> perpendicular to the loopstick. I was having random updates until I
> moved my WWVB clock away from several switching power supplies.
> >The oldest one is 13 years old and is an alarm clock I check daily,
> >in these years I have had it three times take an incorrect time/date
> >probably from interference. It either takes the right time or does
> >not sync, three times in 13 years seems not bad for the simple parity
> >bit protection the protocol uses.
>
> It's a bit more than just the parity bit. Some chips require that the
> correct time be received successfully more than once before it will
> sync. This is a function of the chip design.
> >I think, however, it is somewhat dangerous to have the clocks sync
> >at night *after* you have checked they are set correctly
>
> Sorry, but you don't have a choice as to what time to sync.
Maybe a setting to enable sync only during weekends or only when the alarm function is disabled.
Jeroni Paul
Jul 6, 2015, 3:08:49 PM7/6/15
to
N_Cook wrote:
> Have you had the situation of the displayed time jumping by an hour or two?
> As an alarm clock, losing synch and drifting a second or two , to a
> background quartz crystal clock, is no great problem
I think on one occasion it was several hours off. You could tell it was a wrong bit value as the data would be wrong by a multiple of two.
> Have you had the situation of the displayed time jumping by an hour or two?
> As an alarm clock, losing synch and drifting a second or two , to a
> background quartz crystal clock, is no great problem
Jeff Liebermann
Jul 6, 2015, 7:42:56 PM7/6/15
to
On Mon, 6 Jul 2015 12:03:13 -0700 (PDT), Jeroni Paul
<JERON...@terra.es> wrote:
>Jeff Liebermann wrote:
>> That sounds like the older amplitude modulated system. DCF77 also
>> transmits a phase modulated signal,
>> <https://en.wikipedia.org/wiki/DCF77#Phase_modulation>
>I knew about the phase modulated encoding on the signal but I
>am not sure if any of my clocks use that. The older ones sure
>do not, time ago I dissassembled the oldest alarm clock and
>scoped the signal output from its radio board and I could see
>the 0.1/0.2 sec signal drop.
I haven't looked into the situation for about a year. I also don't
know the situation in Europe. To the best of my limited knowledge,
there are no commodity clocks and no commodity chips being made that
use phase modulation, in the USA. The technology appears to be owned
by Everset, which has done absolutely nothing for several years. I
could find no distributor that carries their chips. My previous
requests for samples, pricing, and delivery were ignored:
<http://eversetclocks.com>
If you find a consumer grade WWVB chip or receiver that do BPSK, I
would be interested.
>There is a long wave radio transmitter in France at 162 kHz that carries time information by phase modulation of its carrier:
>https://en.wikipedia.org/wiki/Allouis_longwave_transmitter
>I find it an efficient way to use existing resources, also you can check for reception by listening with a LW radio.
<https://en.wikipedia.org/wiki/TDF_time_signal>
I'm not sure, but might be able to take the demodulated output of a
162 KHz receiver, and feed it to a decoder made for DCF77, and get
accurate time updates. I searched with Google and found nothing in
the way of a consumer grade DCF time clock.
You can probably get better info from the Time-Nuts mailing list:
<https://www.febo.com/pipermail/time-nuts/>
>Yet, if I had one clock next to a noise source I would expect it to
>sync less times than the rest. But no, there appears to be a random
>distribution.
Nope. WWVB sends the time code at the rate of 1 bit/second (1 baud).
One frame is 60 seconds. Hopefully, the European systems are similar.
<http://www.nist.gov/pml/div688/grp40/wwvbtimecode.cfm>
All it takes is one noise hit every 60 seconds, and you'll receive
nothing. If your local noise source is intermittent or random, then
it's more a matter of timing and bad luck that will determine if the
clock decodes anything useful.
>> It's a bit more than just the parity bit. Some chips require that the
>> correct time be received successfully more than once before it will
>> sync. This is a function of the chip design.
>
>That's what I belived, but then how did it receive incorrect data?
Good question. I don't know. The only time I've seen an incorrect
display was when I was building a WWVB emulator and spraying garbage
data everywhere:
<http://www.instructables.com/id/WWVB-radio-time-signal-generator-for-ATTINY45-or-A/?ALLSTEPS>
However, I've never seen a random erroneous date or time.
>Did it actually receive the same wrong data twice in a row?
Very unlikely that it might receive the same garbage successfully
twice in a row but possible. However, note that the redundancy
requirement is totally in the chip uses, which might vary in
programming and capabilities.
>The algorithm could also check for a reasonable deviation against
>the current setting.
I don't think so. Once it gets a valid time to display, it turns off
the receiver to save battery power. No need to decode more than one
or maybe two frames.
>Maybe a setting to enable sync only during weekends or only
>when the alarm function is disabled.
Personally, I want a graph of signal strength and SNR over a few days
period. Whether anyone is willing to pay for such a feature is
debatable.
<JERON...@terra.es> wrote:
>Jeff Liebermann wrote:
>> That sounds like the older amplitude modulated system. DCF77 also
>> transmits a phase modulated signal,
>> <https://en.wikipedia.org/wiki/DCF77#Phase_modulation>
>I knew about the phase modulated encoding on the signal but I
>am not sure if any of my clocks use that. The older ones sure
>do not, time ago I dissassembled the oldest alarm clock and
>scoped the signal output from its radio board and I could see
>the 0.1/0.2 sec signal drop.
know the situation in Europe. To the best of my limited knowledge,
there are no commodity clocks and no commodity chips being made that
use phase modulation, in the USA. The technology appears to be owned
by Everset, which has done absolutely nothing for several years. I
could find no distributor that carries their chips. My previous
requests for samples, pricing, and delivery were ignored:
<http://eversetclocks.com>
If you find a consumer grade WWVB chip or receiver that do BPSK, I
would be interested.
>There is a long wave radio transmitter in France at 162 kHz that carries time information by phase modulation of its carrier:
>https://en.wikipedia.org/wiki/Allouis_longwave_transmitter
>I find it an efficient way to use existing resources, also you can check for reception by listening with a LW radio.
I'm not sure, but might be able to take the demodulated output of a
162 KHz receiver, and feed it to a decoder made for DCF77, and get
accurate time updates. I searched with Google and found nothing in
the way of a consumer grade DCF time clock.
You can probably get better info from the Time-Nuts mailing list:
<https://www.febo.com/pipermail/time-nuts/>
>Yet, if I had one clock next to a noise source I would expect it to
>sync less times than the rest. But no, there appears to be a random
>distribution.
One frame is 60 seconds. Hopefully, the European systems are similar.
<http://www.nist.gov/pml/div688/grp40/wwvbtimecode.cfm>
All it takes is one noise hit every 60 seconds, and you'll receive
nothing. If your local noise source is intermittent or random, then
it's more a matter of timing and bad luck that will determine if the
clock decodes anything useful.
>> It's a bit more than just the parity bit. Some chips require that the
>> correct time be received successfully more than once before it will
>> sync. This is a function of the chip design.
>
>That's what I belived, but then how did it receive incorrect data?
display was when I was building a WWVB emulator and spraying garbage
data everywhere:
<http://www.instructables.com/id/WWVB-radio-time-signal-generator-for-ATTINY45-or-A/?ALLSTEPS>
However, I've never seen a random erroneous date or time.
>Did it actually receive the same wrong data twice in a row?
twice in a row but possible. However, note that the redundancy
requirement is totally in the chip uses, which might vary in
programming and capabilities.
>The algorithm could also check for a reasonable deviation against
>the current setting.
the receiver to save battery power. No need to decode more than one
or maybe two frames.
>Maybe a setting to enable sync only during weekends or only
>when the alarm function is disabled.
period. Whether anyone is willing to pay for such a feature is
debatable.
Jeff Liebermann
Jul 7, 2015, 2:37:18 PM7/7/15
to
On Sat, 04 Jul 2015 13:10:22 -0400, Phil Hobbs
<ho...@electrooptical.net> wrote:
>On 6/27/2015 10:26 PM, thekma...@gmail.com wrote:
>> I've got the best time sync source of all, courtesy
>> the NIST and WWVB! ;)
>Second best. They adjust those ones to match that yellow thing up in
>the sky. ;)
>Cheers
>Phil Hobbs
Does the NIST use a sundial for a primary time standard? I realize
<ho...@electrooptical.net> wrote:
>On 6/27/2015 10:26 PM, thekma...@gmail.com wrote:
>> I've got the best time sync source of all, courtesy
>> the NIST and WWVB! ;)
>Second best. They adjust those ones to match that yellow thing up in
>the sky. ;)
>Cheers
>Phil Hobbs
that budget cuts have necessitated economy measures, this seems a bit
extreme.
>(We just had a leap second.)
Phil Hobbs
Jul 7, 2015, 3:08:13 PM7/7/15
to
On 07/07/2015 02:37 PM, Jeff Liebermann wrote:
> On Sat, 04 Jul 2015 13:10:22 -0400, Phil Hobbs
> <ho...@electrooptical.net> wrote:
>
>> On 6/27/2015 10:26 PM, thekma...@gmail.com wrote:
>>> I've got the best time sync source of all, courtesy the NIST and
>>> WWVB! ;)
>
>> Second best. They adjust those ones to match that yellow thing up
>> in the sky. ;) Cheers Phil Hobbs
>
> Does the NIST use a sundial for a primary time standard?
In a way, they do. Civil time is adjusted to match mean solar time.
> On Sat, 04 Jul 2015 13:10:22 -0400, Phil Hobbs
> <ho...@electrooptical.net> wrote:
>
>> On 6/27/2015 10:26 PM, thekma...@gmail.com wrote:
>>> I've got the best time sync source of all, courtesy the NIST and
>>> WWVB! ;)
>
>> Second best. They adjust those ones to match that yellow thing up
>> in the sky. ;) Cheers Phil Hobbs
>
> Does the NIST use a sundial for a primary time standard?
> I realize that budget cuts have necessitated economy measures, this
> seems a bit extreme.
>
>> (We just had a leap second.)
>
> Yep. That felt good. I got one second of extra sleep.
Cheers
Phil Hobbs
N_Cook
Jul 8, 2015, 4:22:01 AM7/8/15
to
On 07/07/2015 19:37, Jeff Liebermann wrote:
> On Sat, 04 Jul 2015 13:10:22 -0400, Phil Hobbs
> <ho...@electrooptical.net> wrote:
>
>> On 6/27/2015 10:26 PM, thekma...@gmail.com wrote:
>>> I've got the best time sync source of all, courtesy
>>> the NIST and WWVB! ;)
>
>> Second best. They adjust those ones to match that yellow thing up in
>> the sky. ;)
>> Cheers
>> Phil Hobbs
>
> Does the NIST use a sundial for a primary time standard? I realize
> that budget cuts have necessitated economy measures, this seems a bit
> extreme.
>
>> (We just had a leap second.)
>
> Yep. That felt good. I got one second of extra sleep.
>
>
The new generation of atomic clocks, accurate to 1 second in 15 billion
> On Sat, 04 Jul 2015 13:10:22 -0400, Phil Hobbs
> <ho...@electrooptical.net> wrote:
>
>> On 6/27/2015 10:26 PM, thekma...@gmail.com wrote:
>>> I've got the best time sync source of all, courtesy
>>> the NIST and WWVB! ;)
>
>> Second best. They adjust those ones to match that yellow thing up in
>> the sky. ;)
>> Cheers
>> Phil Hobbs
>
> Does the NIST use a sundial for a primary time standard? I realize
> that budget cuts have necessitated economy measures, this seems a bit
> extreme.
>
>> (We just had a leap second.)
>
> Yep. That felt good. I got one second of extra sleep.
>
>
years,supposedly - how do they know , without a more accurate clock than
that to check it against?
Jeff Liebermann
Jul 8, 2015, 11:38:46 AM7/8/15
to
On Wed, 08 Jul 2015 09:22:02 +0100, N_Cook <div...@tcp.co.uk> wrote:
>The new generation of atomic clocks, accurate to 1 second in 15 billion
>years,supposedly - how do they know , without a more accurate clock than
>that to check it against?
Possibly by consensus. Just make reference measurements on as many
>The new generation of atomic clocks, accurate to 1 second in 15 billion
>years,supposedly - how do they know , without a more accurate clock than
>that to check it against?
inaccurate sources as possible, average them together, and by the
magic of statistics, the average will be more accurate than any
individual measurement. That's because given a sufficiently large
supply of erroneous data, the errors tend to be in opposite directions
and cancel each other. For example, you could average the noon sight
reading from a huge number of sundials or sextants, and the average
will give you NIST grade accuracy.
If this is a problem for you, just buy one of these:
<https://www.kickstarter.com/projects/846511652/the-worlds-first-true-atomic-wristwatch-the-cesium/description>
and you won't have to worry about the sundials and sextants that the
NIST probably secretly uses for calibration. You'll have a personal
time standard that you can trust. Or, just build your own:
<http://www.leapsecond.com/pages/atomic-bill/>
Once you have an accurate clock, all you need to do is decide which
time standard you want to use (LT, GPS, UTC, GMT, GMAT, GAST, SAT,
TAI, Loran, MST, UT, TDT, TBT, TGC/TBC, etc. This might help you
decide how to set your cesium wrist watch:
<http://www.ucolick.org/~sla/leapsecs/timescales.html>
Note that some of these are NOT astronomically based, do not include
leap seconds, were established for political reasons, and don't agree
with other standards. For example, the current differences between
UTC, GPS, and TAI at:
<http://www.leapsecond.com/java/gpsclock.htm>
Also, please note that all of these standards were created and are
managed by various committees, and we all know how ineffective a
committee can be at getting things right.
Perhaps you should just get a wrist sundial:
<https://www.google.com/search?q=wrist+sundial&tbm=isch>
One can't trust the time gods to get it right:
<http://802.11junk.com/jeffl/crud/GPS-vs-UTC.jpg>
Phil Hobbs
Jul 8, 2015, 7:42:30 PM7/8/15
to
and control systematic errors in a measurement. Generally speaking, if
your hydrogen maser and your neighbour's caesium clock and your Russian
brother-in-law's Bose-Einstein condensation agree, you can be pretty
confident. Otherwise it's a real headache.
Cheers
Phil Hobbs
Clifford Heath
Jul 8, 2015, 10:01:38 PM7/8/15
to
My wife is a manager at Australia's National Measurement Institute,
and works directly with the local "Time Lord" who's ultimately
responsible for one of the six atomic clocks that are used to determine
UTC. He's a nice bloke, too.
Of course, nothing in this would allow us to detect a systematic
slow-down in time itself, but if the effect was undetectable, how would
it matter? As long as everything slowed down at the same rate, it would
cause no effect that we could measure. So we compare the six clocks as
they wander around each other, and we try to pick a mean line between
them and call that line "coordinated time". And of course we do research
to try to find a way to build a clock which tracks that mean line better
than current ones do, which is how we got to where we are.
Clifford Heath.
thekma...@gmail.com
Jul 9, 2015, 6:54:07 AM7/9/15
to
Clifford Heath: The biggest variant here is the planet
itself. Earth is slowing down, overall, at a more rapid
rate than any of the world's atomic clocks are speeding
up or slowing down. It's why an "ephemeris" second is
inserted every so many years.
itself. Earth is slowing down, overall, at a more rapid
rate than any of the world's atomic clocks are speeding
up or slowing down. It's why an "ephemeris" second is
inserted every so many years.
Clifford Heath
Jul 9, 2015, 8:17:08 PM7/9/15
to
On 09/07/15 20:54, thekma...@gmail.com wrote:
> Clifford Heath: The biggest variant here is the planet
> itself.
No, the planet is not changing the rate at which time passes, and it's
> Clifford Heath: The biggest variant here is the planet
> itself.
not affecting our ability to measure time.
> Earth is slowing down, overall, at a more rapid
> rate than any of the world's atomic clocks are speeding
> up or slowing down. It's why an "ephemeris" second is
> inserted every so many years.
measure time. Remember I was responding to N_Cook's comment:
"The new generation of atomic clocks, accurate to 1 second in 15 billion
years,supposedly - how do they know , without a more accurate clock than
that to check it against?"
weather affects the sea-level heights, which introduces noise into the
earth's angular moment of inertia, and hence its rate of rotation. That
has nothing however to do with how we know we're measuring time accurately.
Jeff Liebermann
Jul 9, 2015, 9:14:51 PM7/9/15
to
On Fri, 10 Jul 2015 01:37:30 +1000, Clifford Heath
<no....@please.net> wrote:
>The earth's slowing is also somewhat chaotic, inasmuch as equatorial
>weather affects the sea-level heights, which introduces noise into the
>earth's angular moment of inertia, and hence its rate of rotation. That
>has nothing however to do with how we know we're measuring time accurately.
It might help to mention that we have two types of time accuracy. One
<no....@please.net> wrote:
>The earth's slowing is also somewhat chaotic, inasmuch as equatorial
>weather affects the sea-level heights, which introduces noise into the
>earth's angular moment of inertia, and hence its rate of rotation. That
>has nothing however to do with how we know we're measuring time accurately.
is sidereal time, where 12AM on Jan 1 is astronomically correct and is
used to aim telescopes on earth. This is where we says "at the tone,
the time will be... (beep). The other is the length of 1 second,
minute, hour, day... year which is a numerical count of how many
wavelengths of light or cycles of atomic gigahertz
vibrations pass during these intervals also known as atomic time.
The problem is that the two systems don't quite coincide. The current
difference between UTC and International Atomic Time (UTC-TAI) is now
36 sec and growing. The recent leap second just made things worse.
The fun starts when tracking spacecraft in otter space. Not only does
one have to deal with relativistic effects, but one also has to use a
time system that is independent of how the earth spins, wobbles, and
thrashes around. It would be a major disaster if a leap second were
thrown into the timing if you're tracking a spacecraft such as Voyager
1 moving at 17 km/sec (38,000 mph).
There's quite a bit of detail summarized here including what would
happen if GPS (atomic) time were "harmonized" with local time.
<http://www.ucolick.org/~sla/leapsecs/>
Only the top part is up to date but the old stuff is interesting.
Clifford Heath
Jul 9, 2015, 9:38:02 PM7/9/15
to
On 10/07/15 11:14, Jeff Liebermann wrote:
> On Fri, 10 Jul 2015 01:37:30 +1000, Clifford Heath
> <no....@please.net> wrote:
> The fun starts when tracking spacecraft in otter space.
Awesome. Are there any Youtube videos of spacecraft in otter space?
> On Fri, 10 Jul 2015 01:37:30 +1000, Clifford Heath
> <no....@please.net> wrote:
> The fun starts when tracking spacecraft in otter space.
I do love otters, they're my favourite creatures.
;)
Phil Hobbs
Jul 9, 2015, 10:08:00 PM7/9/15
to
On 7/9/2015 9:14 PM, Jeff Liebermann wrote:
> On Fri, 10 Jul 2015 01:37:30 +1000, Clifford Heath
> <no....@please.net> wrote:
>
>> The earth's slowing is also somewhat chaotic, inasmuch as equatorial
>> weather affects the sea-level heights, which introduces noise into the
>> earth's angular moment of inertia, and hence its rate of rotation. That
>> has nothing however to do with how we know we're measuring time accurately.
>
> It might help to mention that we have two types of time accuracy. One
> is sidereal time, where 12AM on Jan 1 is astronomically correct and is
> used to aim telescopes on earth.
Nope. Sidereal time is different from civil (solar) time. The Earth
> On Fri, 10 Jul 2015 01:37:30 +1000, Clifford Heath
> <no....@please.net> wrote:
>
>> The earth's slowing is also somewhat chaotic, inasmuch as equatorial
>> weather affects the sea-level heights, which introduces noise into the
>> earth's angular moment of inertia, and hence its rate of rotation. That
>> has nothing however to do with how we know we're measuring time accurately.
>
> It might help to mention that we have two types of time accuracy. One
> is sidereal time, where 12AM on Jan 1 is astronomically correct and is
> used to aim telescopes on earth.
rotates 365 and change times per year with respect to the Sun, but 366
and (the same) change with respect to the fixed stars. So the two get
out of phase pretty fast.
> This is where we says "at the tone,
> the time will be... (beep). The other is the length of 1 second,
> minute, hour, day... year which is a numerical count of how many
> wavelengths of light or cycles of atomic gigahertz
> vibrations pass during these intervals also known as atomic time.
>
> The problem is that the two systems don't quite coincide. The current
> difference between UTC and International Atomic Time (UTC-TAI) is now
> 36 sec and growing. The recent leap second just made things worse.
Pretty soon the vernal equinox would have been in February.
Personally I think that civil time is more important than atomic time.
Folks who need to know the difference, do.
If we knuckle under to atomic time in civil life, our version of the
Julian problem is that midnight by the clock will soon start occurring
at sundown. The leap second inconvenience principally affects software
developers (and those who trust them). ;)
>
> The fun starts when tracking spacecraft in otter space. Not only does
> one have to deal with relativistic effects, but one also has to use a
> time system that is independent of how the earth spins, wobbles, and
> thrashes around. It would be a major disaster if a leap second were
> thrown into the timing if you're tracking a spacecraft such as Voyager
> 1 moving at 17 km/sec (38,000 mph).
Didn't think so.
Cheers
Phil Hobbs
Clifford Heath
Jul 9, 2015, 10:23:48 PM7/9/15
to
On 10/07/15 12:07, Phil Hobbs wrote:
> On 7/9/2015 9:14 PM, Jeff Liebermann wrote:
> It would be a major disaster if a leap second were
>> thrown into the timing if you're tracking a spacecraft such as Voyager
>> 1 moving at 17 km/sec (38,000 mph).
> You'd be off by 17 km. Is Voyager 1's position known to that accuracy?
> Didn't think so.
And yet if you were aiming at Pluto via a slingshot around Venus, you
> On 7/9/2015 9:14 PM, Jeff Liebermann wrote:
> It would be a major disaster if a leap second were
>> thrown into the timing if you're tracking a spacecraft such as Voyager
>> 1 moving at 17 km/sec (38,000 mph).
> You'd be off by 17 km. Is Voyager 1's position known to that accuracy?
> Didn't think so.
don't want to be 17km off on approach to Venus. I can't do the math, but
I suspect it's rather closer to 17cm.
Jeff Liebermann
Jul 9, 2015, 11:18:18 PM7/9/15
to
On Thu, 09 Jul 2015 22:07:57 -0400, Phil Hobbs
<ho...@electrooptical.net> wrote:
>On 7/9/2015 9:14 PM, Jeff Liebermann wrote:
>> On Fri, 10 Jul 2015 01:37:30 +1000, Clifford Heath
>> <no....@please.net> wrote:
>>
>>> The earth's slowing is also somewhat chaotic, inasmuch as equatorial
>>> weather affects the sea-level heights, which introduces noise into the
>>> earth's angular moment of inertia, and hence its rate of rotation. That
>>> has nothing however to do with how we know we're measuring time accurately.
>>
>> It might help to mention that we have two types of time accuracy. One
>> is sidereal time, where 12AM on Jan 1 is astronomically correct and is
>> used to aim telescopes on earth.
>
>Nope. Sidereal time is different from civil (solar) time. The Earth
>rotates 365 and change times per year with respect to the Sun, but 366
>and (the same) change with respect to the fixed stars. So the two get
>out of phase pretty fast.
Sorry, my mistake.
<ho...@electrooptical.net> wrote:
>On 7/9/2015 9:14 PM, Jeff Liebermann wrote:
>> On Fri, 10 Jul 2015 01:37:30 +1000, Clifford Heath
>> <no....@please.net> wrote:
>>
>>> The earth's slowing is also somewhat chaotic, inasmuch as equatorial
>>> weather affects the sea-level heights, which introduces noise into the
>>> earth's angular moment of inertia, and hence its rate of rotation. That
>>> has nothing however to do with how we know we're measuring time accurately.
>>
>> It might help to mention that we have two types of time accuracy. One
>> is sidereal time, where 12AM on Jan 1 is astronomically correct and is
>> used to aim telescopes on earth.
>
>Nope. Sidereal time is different from civil (solar) time. The Earth
>rotates 365 and change times per year with respect to the Sun, but 366
>and (the same) change with respect to the fixed stars. So the two get
>out of phase pretty fast.
>> The problem is that the two systems don't quite coincide. The current
>> difference between UTC and International Atomic Time (UTC-TAI) is now
>> 36 sec and growing. The recent leap second just made things worse.
>
>Well, worse if you don't think that the Gregorian reform was an advance.
> Pretty soon the vernal equinox would have been in February.
know how to tweak the date so that it matches the solar calendar. That
was fine for farmers and bankers, but didn't do much for the church,
which had the bad taste to celebrate their holidays by the calendar
month and date. Most everyone else used the signs of the zodiac to
set the beginning of the month. That worked well for the GUM (great
unwashed masses) except that the church equated the zodiac with pagan
religions, alchemy and witchcraft, so that wasn't going to work. A
pope previous to Gregory XIII tried to switch the holidays to the
zodiac months (can't find the name) but gave up before going public.
I suspect that Gregory XIII must have had second throughts when he
allowed the astronomers to fix the calendar. At least they named it
after him, so I guess he was happy.
Incidentally, if you want a really screwed up calendar, try the Hebrew
calendar, which adds an extra month every 2 or 3 years, every 7 of 11
years.
<https://en.wikipedia.org/wiki/Hebrew_calendar>
There's nothing like a duplicated month (adar) to create confusion.
>Personally I think that civil time is more important than atomic time.
>Folks who need to know the difference, do.
>
>If we knuckle under to atomic time in civil life, our version of the
>Julian problem is that midnight by the clock will soon start occurring
>at sundown. The leap second inconvenience principally affects software
>developers (and those who trust them). ;)
can have it's own time standard, I see no reason why they can't expand
theirs to a calendar standard. You just pick the calendar that is
appropriate for whatever you're doing. It's not much different than
the US before the railroads, where every town had it's own time and
DST standard.
Yeah, there were some hiccups in 2012.
<http://www.wired.com/2012/07/leap-second-bug-wreaks-havoc-with-java-linux/>
<http://www.wired.com/2012/07/leap-second-glitch-explained/>
I missed the fire drill, but still managed to get wakened by a
customer wanting to know why their backup failed. Stupid me had set
cron to start the backup exactly at midnight. That worked, but one
second later, it started a 2nd backup during the leap second. Why, I
don't know, but that's what the log files showed. I killed both
processes and started over.
>> The fun starts when tracking spacecraft in otter space. Not only does
>> one have to deal with relativistic effects, but one also has to use a
>> time system that is independent of how the earth spins, wobbles, and
>> thrashes around. It would be a major disaster if a leap second were
>> thrown into the timing if you're tracking a spacecraft such as Voyager
>> 1 moving at 17 km/sec (38,000 mph).
>
>You'd be off by 17 km. Is Voyager 1's position known to that accuracy?
> Didn't think so.
rotation of the earth.
degrees = 17km/40,075km * 360 degrees = 0.15 degrees
Let's see if that works. Voyager 1 and 2 uses the DSN (deep space
network) with 34 or 70 meter dishes at about 8 GHz. That's about 67dB
gain and a -3db beamwidth of about 0.07 degrees for the 34 meter dish,
and 73 db gain and 0.04 degree beamwidth for the 70 meter dish. Since
the DSN tracks the rotation of the earth, a change of 0.15 degrees
would move the main lobe sufficiently to miss the spacecraft.
<http://www.satsig.net/pointing/antenna-beamwidth-calculator.htm>
<http://www.uhf-satcom.com/misc/datasheet/dh2va.pdf>
Jeff Liebermann
Jul 9, 2015, 11:33:37 PM7/9/15
to
On Fri, 10 Jul 2015 02:58:26 +1000, Clifford Heath
<https://www.youtube.com/results?search_query=otter+in+space>
Photos of some otter space otters:
<https://www.google.com/search?q=space+otter&tbm=isch>
I don't really like otters. Years ago, I was diving off Monastary
Beach in Carmel, CA. There was an otter floating on the surface
sleeping. My dive partner decided to poke the otter with a pole. It
looked down at us, and went back to sleep. However, my partner kept
poking the otter until it became irritated. It dived down under us,
came up, and bit me in the buttocks though my wet suit. It wasn't
much of a bite, but did manage to ruin my day.
These days, I look at them with otter contempt.
<no....@please.net> wrote:
>On 10/07/15 11:14, Jeff Liebermann wrote:
>> On Fri, 10 Jul 2015 01:37:30 +1000, Clifford Heath
>> <no....@please.net> wrote:
>> The fun starts when tracking spacecraft in otter space.
>Awesome. Are there any Youtube videos of spacecraft in otter space?
>I do love otters, they're my favourite creatures.
Yep:
>On 10/07/15 11:14, Jeff Liebermann wrote:
>> On Fri, 10 Jul 2015 01:37:30 +1000, Clifford Heath
>> <no....@please.net> wrote:
>> The fun starts when tracking spacecraft in otter space.
>Awesome. Are there any Youtube videos of spacecraft in otter space?
>I do love otters, they're my favourite creatures.
<https://www.youtube.com/results?search_query=otter+in+space>
Photos of some otter space otters:
<https://www.google.com/search?q=space+otter&tbm=isch>
I don't really like otters. Years ago, I was diving off Monastary
Beach in Carmel, CA. There was an otter floating on the surface
sleeping. My dive partner decided to poke the otter with a pole. It
looked down at us, and went back to sleep. However, my partner kept
poking the otter until it became irritated. It dived down under us,
came up, and bit me in the buttocks though my wet suit. It wasn't
much of a bite, but did manage to ruin my day.
These days, I look at them with otter contempt.
Clifford Heath
Jul 10, 2015, 12:33:43 AM7/10/15
to
On 10/07/15 13:33, Jeff Liebermann wrote:
> On Fri, 10 Jul 2015 02:58:26 +1000, Clifford Heath
> <no....@please.net> wrote:
>> On 10/07/15 11:14, Jeff Liebermann wrote:
>>> The fun starts when tracking spacecraft in otter space.
>> Awesome. Are there any Youtube videos of spacecraft in otter space?
>> I do love otters, they're my favourite creatures.
> On Fri, 10 Jul 2015 02:58:26 +1000, Clifford Heath
> <no....@please.net> wrote:
>> On 10/07/15 11:14, Jeff Liebermann wrote:
>>> The fun starts when tracking spacecraft in otter space.
>> Awesome. Are there any Youtube videos of spacecraft in otter space?
>> I do love otters, they're my favourite creatures.
> Photos of some otter space otters:
> <https://www.google.com/search?q=space+otter&tbm=isch>
> I don't really like otters.
I've only seen sea otters once, on a visit to Monterey.
> <https://www.google.com/search?q=space+otter&tbm=isch>
> I don't really like otters.
I guess you also are more fond of animals you don't have locally.
The common otter is super cute. One day, I want to learn how to ot.
it looks like fun.
N_Cook
Jul 10, 2015, 3:34:57 AM7/10/15
to
midnight start is just a hangover from the Romans, so sundown start is
no great problem
thekma...@gmail.com
Jul 10, 2015, 5:59:38 AM7/10/15
to
Clifford Heath wrote: "No, the planet is not changing
If the planet is gradually slowing down,
over millions of years as reported, the
period of time from noon to noon(or
midnight to midnight), is getting LONGER.
Our hyper-accurate master clocks have
to account for that somehow.
"Yes, but that has nothing to do with how we improve our ability to
measure time. Remember I was responding to N_Cook's comment:
"The new generation of atomic clocks, accurate to 1 second in 15 billion
years,supposedly - how do they know , without a more accurate clock than
that to check it against?" "
"The earth's slowing is also somewhat chaotic, inasmuch as equatorial
weather affects the sea-level heights, which introduces noise into the
earth's angular moment of inertia, and hence its rate of rotation. That
has nothing however to do with how we know we're measuring time accurately. "
OF COURSE IT DOES!! If our super-accurate
clocks don't account for an inconsistent Earth,
then sunrises, sunsets, and everything else
will start happening later & later by those clocks.
Sunrise in June in Connecticut will come at
5:23, 5:24(Daylight Time)instead of 5:20 as it
has for decades, and sunset - 8:32, 8:33,
instead of 8:30 as it has for years. It's
only adding those periodic seconds that
maintains that symmetry.
That's because of PLANET drift, not clock
drift. And overall, it is slowing down, not
speeding up.
the rate at which time passes, and it's not affecting our
ability to measure time. "
HOW can you make such a statement???
ability to measure time. "
If the planet is gradually slowing down,
over millions of years as reported, the
period of time from noon to noon(or
midnight to midnight), is getting LONGER.
Our hyper-accurate master clocks have
to account for that somehow.
"Yes, but that has nothing to do with how we improve our ability to
measure time. Remember I was responding to N_Cook's comment:
"The new generation of atomic clocks, accurate to 1 second in 15 billion
years,supposedly - how do they know , without a more accurate clock than
that to check it against?" "
"The earth's slowing is also somewhat chaotic, inasmuch as equatorial
weather affects the sea-level heights, which introduces noise into the
earth's angular moment of inertia, and hence its rate of rotation. That
has nothing however to do with how we know we're measuring time accurately. "
clocks don't account for an inconsistent Earth,
then sunrises, sunsets, and everything else
will start happening later & later by those clocks.
Sunrise in June in Connecticut will come at
5:23, 5:24(Daylight Time)instead of 5:20 as it
has for decades, and sunset - 8:32, 8:33,
instead of 8:30 as it has for years. It's
only adding those periodic seconds that
maintains that symmetry.
That's because of PLANET drift, not clock
drift. And overall, it is slowing down, not
speeding up.
Clifford Heath
Jul 10, 2015, 6:48:23 AM7/10/15
to
On 10/07/15 19:59, thekma...@gmail.com wrote:
> Clifford Heath wrote: "No, the planet is not changing
> the rate at which time passes, and it's not affecting our
> ability to measure time. "
>
> HOW can you make such a statement???
> If the planet is gradually slowing down,
> over millions of years as reported, the
> period of time from noon to noon(or
> midnight to midnight), is getting LONGER.
Whoosh! You completely missed the point.
> Clifford Heath wrote: "No, the planet is not changing
> the rate at which time passes, and it's not affecting our
> ability to measure time. "
>
> HOW can you make such a statement???
> If the planet is gradually slowing down,
> over millions of years as reported, the
> period of time from noon to noon(or
> midnight to midnight), is getting LONGER.
The reason we know it's getting longer is because
we have clocks that *aren't* slowing down. I was
talking entirely about *how we know* they aren't
slowing down.
> Our hyper-accurate master clocks have
> to account for that somehow.
and we decide what numbers to assign to the days,
hours, minutes, seconds. The *numbers* are not
the *time*.
> "The earth's slowing is also somewhat chaotic, inasmuch as equatorial
> weather affects the sea-level heights, which introduces noise into the
> earth's angular moment of inertia, and hence its rate of rotation. That
> has nothing however to do with how we know we're measuring time accurately. "
>
> OF COURSE IT DOES!! If our super-accurate
> clocks don't account for an inconsistent Earth,
> then sunrises, sunsets, and everything else
> will start happening later & later by those clocks.
That is why we need leap seconds etc, to
adjust the *numbering* to match the planet's
motion. But adjusting the numbering doesn't
make time pass slower or faster.
thekma...@gmail.com
Jul 10, 2015, 7:06:56 AM7/10/15
to
On Friday, July 10, 2015 at 6:48:23 AM UTC-4, Clifford Heath wrote:
to match its movement with precision, repetitive
movements.
>
> > Our hyper-accurate master clocks have
> > to account for that somehow.
>
> No,they don't. They just count the time passing,
> and we decide what numbers to assign to the days,
> hours, minutes, seconds. The *numbers* are not
> the *time*.
>
> > "The earth's slowing is also somewhat chaotic, inasmuch as equatorial
> > weather affects the sea-level heights, which introduces noise into the
> > earth's angular moment of inertia, and hence its rate of rotation. That
> > has nothing however to do with how we know we're measuring time accurately. "
> >
> > OF COURSE IT DOES!! If our super-accurate
> > clocks don't account for an inconsistent Earth,
> > then sunrises, sunsets, and everything else
> > will start happening later & later by those clocks.
>
> And that is *exactly* what is happening.
> That is why we need leap seconds etc, to
> adjust the *numbering* to match the planet's
> motion. But adjusting the numbering doesn't
> make time pass slower or faster.
I never said it did. If we as a species never
had clocks at all, I'd guess we all just get used
to this light & dark cycle called days getting
longer and longer all the time and not even think
twice about it.
> On 10/07/15 19:59com wrote:
> > Clifford Heath wrote: "No, the planet is not changing
> > the rate at which time passes, and it's not affecting our
> > ability to measure time. "
> >
> > HOW can you make such a statement???
> > If the planet is gradually slowing down,
> > over millions of years as reported, the
> > period of time from noon to noon(or
> > midnight to midnight), is getting LONGER.
>
> Whoosh! You completely missed the point.
>
> The reason we know it's getting longer is because
> we have clocks that *aren't* slowing down. I was
> talking entirely about *how we know* they aren't
> slowing down.
The Earth is a natural, living object. It's impossible
> > Clifford Heath wrote: "No, the planet is not changing
> > the rate at which time passes, and it's not affecting our
> > ability to measure time. "
> >
> > HOW can you make such a statement???
> > If the planet is gradually slowing down,
> > over millions of years as reported, the
> > period of time from noon to noon(or
> > midnight to midnight), is getting LONGER.
>
> Whoosh! You completely missed the point.
>
> The reason we know it's getting longer is because
> we have clocks that *aren't* slowing down. I was
> talking entirely about *how we know* they aren't
> slowing down.
to match its movement with precision, repetitive
movements.
>
> > Our hyper-accurate master clocks have
> > to account for that somehow.
>
> No,they don't. They just count the time passing,
> and we decide what numbers to assign to the days,
> hours, minutes, seconds. The *numbers* are not
> the *time*.
>
> > "The earth's slowing is also somewhat chaotic, inasmuch as equatorial
> > weather affects the sea-level heights, which introduces noise into the
> > earth's angular moment of inertia, and hence its rate of rotation. That
> > has nothing however to do with how we know we're measuring time accurately. "
> >
> > OF COURSE IT DOES!! If our super-accurate
> > clocks don't account for an inconsistent Earth,
> > then sunrises, sunsets, and everything else
> > will start happening later & later by those clocks.
>
> And that is *exactly* what is happening.
> That is why we need leap seconds etc, to
> adjust the *numbering* to match the planet's
> motion. But adjusting the numbering doesn't
> make time pass slower or faster.
had clocks at all, I'd guess we all just get used
to this light & dark cycle called days getting
longer and longer all the time and not even think
twice about it.
N_Cook
Jul 10, 2015, 9:21:18 AM7/10/15
to
from the sensory deprivation experiments conducted in caves. Everyone
else, in normally life, gets sync'd to this artificial 24 hour system.
thekma...@gmail.com
Jul 10, 2015, 9:25:19 AM7/10/15
to
On Friday, July 10, 2015 at 9:21:18 AM UTC-4, N_Cook wrote:
I suppose 24 developed out of need for dividing the day evenly. Of course, that doesn't explain the 7-day week. LOL
jf...@my-deja.com
Jul 10, 2015, 10:25:14 AM7/10/15
to
On Friday, July 10, 2015 at 6:25:19 AM UTC-7, thekma...@gmail.com wrote:
> I suppose 24 developed out of need for dividing the day
> evenly. Of course, that doesn't explain the 7-day week. LOL
The French Revolution also metricated the clock (10 hours in a day, 100 minutes in an hour, 100 seconds in a minture) and the calendar (3 decades in a month, 10 days in a decade, plus complementary days. This appears to be one part of the metric system that was not widely adopted.
> I suppose 24 developed out of need for dividing the day
> evenly. Of course, that doesn't explain the 7-day week. LOL
Phil Hobbs
Jul 10, 2015, 10:45:21 AM7/10/15
to
measurement anyway. Astronomers and orbital mechanics bods are used to
having to worry about different types of time scale--ephemeris time,
UT1, UT2, UTC, and so on.
The movement to abolish leap seconds is just another special interest
group.
N_Cook
Jul 10, 2015, 11:11:26 AM7/10/15
to
Jeff Liebermann
Jul 10, 2015, 11:16:59 AM7/10/15
to
On Fri, 10 Jul 2015 12:08:45 +1000, Clifford Heath
<no....@please.net> wrote:
>And that is *exactly* what is happening.
>That is why we need leap seconds etc, to
>adjust the *numbering* to match the planet's
>motion. But adjusting the numbering doesn't
>make time pass slower or faster.
Sure it does. If you watch the clock, time will seem to go slower.
<no....@please.net> wrote:
>And that is *exactly* what is happening.
>That is why we need leap seconds etc, to
>adjust the *numbering* to match the planet's
>motion. But adjusting the numbering doesn't
>make time pass slower or faster.
Surely there's a standard for Universal Perceived Time.
I don't want to be late, I simply set my clocks to about 15 minutes
ahead. That would be a Leap Quarter Hour.
It also works in the other direction. If I'm expecting a package
delivery, it will always be late, the result of time dilation due to
the movement of the package. I've also noticed that the faster
someone appears to be working towards a deadline, the further behind
the project slips, again the result of time dilation and movement.
Jeff Liebermann
Jul 10, 2015, 12:39:02 PM7/10/15
to
On Fri, 10 Jul 2015 06:25:16 -0700 (PDT), thekma...@gmail.com
wrote:
>> The innate human biological clock is nearer 25 hour-day than 24 hours,
>> from the sensory deprivation experiments conducted in caves. Everyone
>> else, in normally life, gets sync'd to this artificial 24 hour system.
Mine used to be synchronized to the television show schedule.
>I suppose 24 developed out of need for dividing the day evenly.
>Of course, that doesn't explain the 7-day week. LOL
"Why are there 24 hours in a day?"
<http://www.abc.net.au/science/articles/2011/11/15/3364432.htm>
The ancient Egyptians apparently were on a decimal system but got
derailed by a special interest faction in their standards committee
that favored a 12 hr day. At least they tried. I would give the
blame/credit to the Babylonians.
wrote:
>> The innate human biological clock is nearer 25 hour-day than 24 hours,
>> from the sensory deprivation experiments conducted in caves. Everyone
>> else, in normally life, gets sync'd to this artificial 24 hour system.
>I suppose 24 developed out of need for dividing the day evenly.
>Of course, that doesn't explain the 7-day week. LOL
<http://www.abc.net.au/science/articles/2011/11/15/3364432.htm>
The ancient Egyptians apparently were on a decimal system but got
derailed by a special interest faction in their standards committee
that favored a 12 hr day. At least they tried. I would give the
blame/credit to the Babylonians.
jf...@my-deja.com
Jul 10, 2015, 1:18:54 PM7/10/15
to
On Friday, July 10, 2015 at 9:39:02 AM UTC-7, Jeff Liebermann wrote:
> "Why are there 24 hours in a day?"
> <http://www.abc.net.au/science/articles/2011/11/15/3364432.htm>
> The ancient Egyptians apparently were on a decimal system but
> got derailed by a special interest faction in their standards
> committee that favored a 12 hr day. At least they tried.
> I would give the blame/credit to the Babylonians.
>
> --
> Jeff Liebermann je...@cruzio.com
> 150 Felker St #D http://www.LearnByDestroying.com
> Santa Cruz CA 95060 http://802.11junk.com
> Skype: JeffLiebermann AE6KS 831-336-2558
The Babylonians got it from some alien astronauts who had six fingers on each hand and six toes on each foot. It must be true. I read it on the internet.
> "Why are there 24 hours in a day?"
> <http://www.abc.net.au/science/articles/2011/11/15/3364432.htm>
> The ancient Egyptians apparently were on a decimal system but
> got derailed by a special interest faction in their standards
> committee that favored a 12 hr day. At least they tried.
> I would give the blame/credit to the Babylonians.
>
> --
> Jeff Liebermann je...@cruzio.com
> 150 Felker St #D http://www.LearnByDestroying.com
> Santa Cruz CA 95060 http://802.11junk.com
> Skype: JeffLiebermann AE6KS 831-336-2558
Jeff Liebermann
Jul 10, 2015, 8:04:00 PM7/10/15
to
On Fri, 10 Jul 2015 08:34:54 +0100, N_Cook <div...@tcp.co.uk> wrote:
>IIRC the Etruscan day started at midday, the Jewish day at 6am, the
>midnight start is just a hangover from the Romans, so sundown start is
>no great problem
No, it's not 6AM. The Hebrew calendar tries to follow Ye Olde
>IIRC the Etruscan day started at midday, the Jewish day at 6am, the
>midnight start is just a hangover from the Romans, so sundown start is
>no great problem
Testament, where God created the heavens and the Earth on the first
day, but waited until the 4th day to create the sun. Although "Let
there be light" implies that there was light coming from somewhere
during the first 3 days, it obviously didn't come from the sun, which
first appeared on the 4th day. That also begs the question of how God
knew how long to call a day, since the earth didn't have a sun handy
with which to tell time. However, if the first 3 days of light came
from the sun, it must have taken 4 days for the light to reach Earth,
which suggests that God may have done some major remodeling of the
solar system before turning on the lights.
Anyway, the Bible says that the first day started with darkness and
ended in light, thus making the Hebrew calendar start at sundown, the
beginning of darkness.
More drivel: New Years day has changed through history:
<http://www.simpletoremember.com/articles/a/newyearshistory/>
Jan 1 was the day that Jesus was circumcised:
<https://en.wikipedia.org/wiki/Circumcision_of_Jesus>
Jeff Liebermann
Jul 10, 2015, 8:17:44 PM7/10/15
to
On Fri, 10 Jul 2015 10:18:50 -0700 (PDT), "jf...@my-deja.com"
<jf...@my-deja.com> wrote:
>On Friday, July 10, 2015 at 9:39:02 AM UTC-7, Jeff Liebermann wrote:
>> "Why are there 24 hours in a day?"
>> <http://www.abc.net.au/science/articles/2011/11/15/3364432.htm>
>> The ancient Egyptians apparently were on a decimal system but
>> got derailed by a special interest faction in their standards
>> committee that favored a 12 hr day. At least they tried.
>> I would give the blame/credit to the Babylonians.
<jf...@my-deja.com> wrote:
>On Friday, July 10, 2015 at 9:39:02 AM UTC-7, Jeff Liebermann wrote:
>> "Why are there 24 hours in a day?"
>> <http://www.abc.net.au/science/articles/2011/11/15/3364432.htm>
>> The ancient Egyptians apparently were on a decimal system but
>> got derailed by a special interest faction in their standards
>> committee that favored a 12 hr day. At least they tried.
>> I would give the blame/credit to the Babylonians.
>The Babylonians got it from some alien astronauts who had
>six fingers on each hand and six toes on each foot.
No visitors from otter space required. Six fingers and/or toes not so
>six fingers on each hand and six toes on each foot.
rare:
<https://www.google.com/search?q=six+fingers+and+toes&tbm=isch>
<https://en.wikipedia.org/wiki/Polydactyly>
Please note that we all have 11 fingers total. Start counting down on
one hand with 10 - 9 - 8 - 7 - 6 and 5 more on the other hand makes
11.
>It must be true. I read it on the internet.
be successful.
Jeroni Paul
Jul 11, 2015, 7:07:51 AM7/11/15
to
Jeff Liebermann wrote:
> The only time I've seen an incorrect
> display was when I was building a WWVB emulator and spraying garbage
> data everywhere:
> <http://www.instructables.com/id/WWVB-radio-time-signal-generator-for-ATTINY45-or-A/?ALLSTEPS>
> However, I've never seen a random erroneous date or time.
Nice project. Now I think of someone trying to increase its range with a power stage and going way too far...
This reminds me of these projects:
http://www.erikyyy.de/tempest/
http://bellard.org/dvbt/
I guess something similar could be done to generate a DCF77/WWVB signal.
> >The algorithm could also check for a reasonable deviation against
> >the current setting.
>
> I don't think so. Once it gets a valid time to display, it turns off
> the receiver to save battery power. No need to decode more than one
> or maybe two frames.
Oh, I think I didn't explain it right. I meant an additional check for valid data would be to verify that the received time falls within a reasonable window around the current time. If the clock knows that now is 1:00am +/- 2 minutes it makes no sense to receive 7:42am and take that as valid time.
So the algorithm would be: if there was never a sync before or the user set the time manually => belive whatever time is received, in this case decoding of several minutes can be done as an extra check).
Otherwise (there was a valid sync before and clock time was not changed manually) check the received time is within a few minutes of clock time.
That would help save battery since decoding a single minute would be enough for safe daily sync.
> The only time I've seen an incorrect
> display was when I was building a WWVB emulator and spraying garbage
> data everywhere:
> <http://www.instructables.com/id/WWVB-radio-time-signal-generator-for-ATTINY45-or-A/?ALLSTEPS>
> However, I've never seen a random erroneous date or time.
Nice project. Now I think of someone trying to increase its range with a power stage and going way too far...
This reminds me of these projects:
http://www.erikyyy.de/tempest/
http://bellard.org/dvbt/
I guess something similar could be done to generate a DCF77/WWVB signal.
> >The algorithm could also check for a reasonable deviation against
> >the current setting.
>
> I don't think so. Once it gets a valid time to display, it turns off
> the receiver to save battery power. No need to decode more than one
> or maybe two frames.
Oh, I think I didn't explain it right. I meant an additional check for valid data would be to verify that the received time falls within a reasonable window around the current time. If the clock knows that now is 1:00am +/- 2 minutes it makes no sense to receive 7:42am and take that as valid time.
So the algorithm would be: if there was never a sync before or the user set the time manually => belive whatever time is received, in this case decoding of several minutes can be done as an extra check).
Otherwise (there was a valid sync before and clock time was not changed manually) check the received time is within a few minutes of clock time.
That would help save battery since decoding a single minute would be enough for safe daily sync.
Jeff Liebermann
Jul 11, 2015, 2:01:35 PM7/11/15
to
On Sat, 11 Jul 2015 04:07:45 -0700 (PDT), Jeroni Paul
<JERON...@terra.es> wrote:
>Nice project. Now I think of someone trying to increase its
>range with a power stage and going way too far...
It's amazingly easy to do, but at 60 KHz, the range would be rather
<JERON...@terra.es> wrote:
>Nice project. Now I think of someone trying to increase its
>range with a power stage and going way too far...
limited. It takes some serious power to produce a field strength
sufficiently strong to overcome atmospheric noise levels.
>I guess something similar could be done to generate a DCF77/WWVB signal.
generate the code. You can also buy IRIG-H (used by WWVB etc) time
code generators that should work.
<https://en.wikipedia.org/wiki/IRIG_timecode>
For example:
<http://www.gigatest.net/datum/tymmachine_7000.htm>
Just add an AM modulated RF signal generator to produce the 60 KHz,
and you're well on your way to becoming the local time lord.
>So the algorithm would be: if there was never a sync before or the
>user set the time manually => belive whatever time is received,
>in this case decoding of several minutes can be done as an extra check).
>Otherwise (there was a valid sync before and clock time was not
>changed manually) check the received time is within a few minutes of
>clock time.
>That would help save battery since decoding a single minute would
>be enough for safe daily sync.
exactly 1 minute long, and there's no way to obtain identical data
twice in a row, simply truncating the data to eliminate the minutes
and seconds data, would give the clock an hour to obtain to
identically truncated receptions. No need for a complex sanity check
algorithm. Of course, the receiver would not be turned on for the
full hour, but a successful spot check a few minutes after the first
successful reception would be sufficient to conserve battery power. I
suspect that's the way it's done in the C-Max chips, but I'm not sure.
Diversion: I worked on a failed proposal for an accurate time
distribution system that used carrier current repeaters (i.e.
HomePlug) to distribute the data. The time source was the GOES
satellite system, which belched time sync data on 468.xxx MHz. The
satellite data was to be retransmitted at the home or office over
power line carrier current frequencies (now Home Plug) to any device
that needs accurate time (clocks, computahs, appliances, test
equipment, cell sites, SONET, etc). The difference with other radio
clock systems is that this one would be continuous, not updated
erratically. The GOES signal was strong (+45.5dBm EIRP) that a simple
RHCP patch antenna aimed towards the bird was sufficient. I had it
mostly working when NASA announced that it was going to pull the plug
in 2004. Oh well. Today, it's done with GPSDO driven clocks with
much better accuracy.
GOES time receivers.
http://www.leapsecond.com/pages/goes/
TrueTime 468-DC GOES Time Receiver
http://www.leapsecond.com/museum/468-dc/theory.htm
468-DC SATELLITE CLOCK
http://www.ebay.com/gds/468-DC-SATELLITE-CLOCK-/10000000006640775/g.html
Meteorological Satellite Frequencies
<http://mdkenny.customer.netspace.net.au/metsat_frequencies.html#goes-n>
Phil Hobbs
Jul 11, 2015, 3:02:44 PM7/11/15
to
clocks to aim the DSN, but that's a fantasy. Orbital mechanics bods are
all over this timekeeping stuff. It's the stupid software developers
who don't know or don't care.
Phil Hobbs
Jul 11, 2015, 3:06:20 PM7/11/15
to
move at all--leap seconds keep civil time in synchrony with mean solar
time to within a couple of PPM of a day.
Wanting to get rid of leap seconds is a classical example of a special
interest group trying to seize control.
Not that that's unusual, especially these days.
Jeff Liebermann
Jul 12, 2015, 2:22:09 PM7/12/15
to
<http://descanso.jpl.nasa.gov/performmetrics/DSN_NavSysAccuracy.pdf>
<http://descanso.jpl.nasa.gov/performmetrics/perfmetric.html>
It shows the current DSN aiming accuracy at 0.1 nanorads or 15 meters
at 1 AU distance. Voyager 1 is currently at 131 AU distance:
<http://voyager.jpl.nasa.gov/where/>
That grinds out to an accuracy of 2 km meters at a range of 19.6
billion km. Yes, NASA does know the position of Voyager 1 to less
than 17 km.
Incidentally, that an angular resolution of:
arctan(2/19.6*10^9) = 0.000000006 degrees (or 6*10^-9 deg)
A 0.15 degree error, caused by a leap second, would produce a rather
astronomical pointing error.
Wow, that's impressive (or I mangled the math again).
Michael A. Terrell
Jul 22, 2015, 8:41:52 AM7/22/15
to
Jeff Liebermann wrote:
>
> Personally, I want a graph of signal strength and SNR over a few days
> period. Whether anyone is willing to pay for such a feature is
> debatable.
Fluke must have thought so. Their 207 receiver has a strip chart
recorder. Microdyne used one for decades as part of their time &
frequency standard, before replacing it with a GPS derived system for
the in house cal lab, and for their Electrical Engineering department. I
built a 64 output 10 MHz distribution amp to add the production areas to
the system, somewhere around 2000.
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