WTF with my computer clock?

[isw]

In article <4a89a36b$0$7465$822641b3@news.adtechcomputers.com>,
David Nebenzahl <nobody@but.us.chickens> wrote:

On 8/16/2009 10:12 PM isw spake thus:

Functionally impossible. By adding money, you can reduce the drift rate
but you can't make it zero. Period.

I don't care about zero. One minute a month is plenty accurate enough
for me.

Just use NTP. And *stay away* from the stratum one servers like NIST;
they have better things to do than keep your computer's clock on
time.

You're admonishing me not to use NIST? Why?

After all, they offer this service to me. See
http://tf.nist.gov/service/its.htm:

The NIST Internet Time Service (ITS) allows users to synchronize
computer clocks via the Internet. The time information provided by
the service is directly traceable to UTC(NIST). The service responds
to time requests from any Internet client in several formats
including the DAYTIME, TIME, and NTP protocols.

So why shouldn't I use them?

If you need stratum one precision, NIST is not a good choice unless you
live near them; you should choose a stratum one server near to you. If
you don't need that precision but just want your computer's clock to be
decently close all the time, why put an unnecessary load on any of the
stratum one (i.e. high precision) servers? Leave them alone to serve
folks who *do* need that accuracy.

There's a decent number of lower stratum servers that sync to NIST and
some of the other high precision servers. They are specifically intended
to be used by the folks who don't need their computer to be within a
fraction of a microsecond of "actual time".

Lots more info here: http://www.pool.ntp.org/

Isaac

 

[isw]

In article <e2iol6-1er.ln1@radagast.org>,
dplatt@radagast.org (Dave Platt) wrote:

>,
isw <isw@witzend.com> wrote:

Functionally impossible. By adding money, you can reduce the drift rate
but you can't make it zero. Period. Just use NTP.

Or, if you prefer something stand-alone which will give you a good time
reference if your network connection is down: use GPS.

Except I don't see how you can call something that *must* receive radio
signals all the time "stand alone" (I guess you could say that it's on a
"wireless network"). And of course, GPS time is ultimately synchronized
to that same aggregation of stratum 0 clocks as all the other servers
we've been talking about.

That said, GPS is a very good way to distribute precision time. You can
see 4-inch mushroom-shaped things on top of buildings at the base of
cellphone towers all over the place; they're GPS receivers (often two
for redundancy) used for getting the signals timed properly before
injecting them into the telco network.

Isaac

 

[isw]

In article <508c1bae1adave@davenoise.co.uk>,
"Dave Plowman (News)" <dave@davenoise.co.uk> wrote:

In article <4a88a59a$0$7469$822641b3@news.adtechcomputers.com>,
David Nebenzahl <nobody@but.us.chickens> wrote:
I agree that for most a minute per month is reasonable but I would
expect the same accuracy as my $29.99 Timex wristwatch which is more
like a second a month.

So that kinda begs the question of why computer mfrs. can't (or won't)
include clocks that are at *least* as accurate as a Timex, no? Wouldn't
a computah be a more compelling reason for a more accurate clock? (I
know, $$$ bottom line, right?)

Wonder if it's because a wrist watch is kept at a pretty constant
temperature via the skin?

Bingo!

Isaac

 

[Sylvia Else]

isw wrote:

In article <508c2b53d8dave@davenoise.co.uk>,
"Dave Plowman (News)" <dave@davenoise.co.uk> wrote:

In article <9V8im.353345$jW1.145448@newsfe22.ams2>,
Arfa Daily <arfa.daily@ntlworld.com> wrote:
That's my feeling too. It definitely used to be much better here in the
UK, than it is now. If a programme was billed to start at 8pm, then it
pretty much did.
Pretty much sums it up. But in those days few had dead accurate clocks
which are so common now.

Actually,they were very close.

Western Union clocks all over the country were almost always all synched
to within a second or so. The technique was to use clocks (those big
things with the red sweep hand you may have seen in a broadcast studio)
that were basically pretty good, and to synch them to a remote timebase
from time to time.

The clocks were pendulum timed and electrically wound (couple of big dry
cells inside), and every one of them had a leased-line connection to the
nearest WU office, and from there to a national site.

Every 12 hours (AFAIR), Western Union sent a pulse down the wire that
"jammed" the sweep hands of all those clocks to 12 (and illuminated a
little red light behind the clock face so you could see that your time
was being corrected). I don't think the minute and hour hands were
controlled. It was up to the engineering personnel in each station to
twiddle their clocks' pendulums so the clocks could run within a second
or two in 12 hours -- not at all difficult for a good pendulum clock.

So as long as the accounting department paid the WU bill, you could join
your network or insert a local commercial with almost perfect accuracy.

Isaac

In the UK, or in London at least, the mains frequency was maintained
with a very accurate long term average, so that synchronous mains clocks
just stayed correct.

Sometimes, after short power cuts, the frequency was increased to bring
such clocks back to the correct time. Which was actually a bit of a
nuiscance for us - we had clocks that weren't self starting (a
reflection of the rareness of power outages in those days), so after a
power cut, we'd set the clocks correctly and start them, only to find
them gaining.

It seems a backward step that now, forty or so years later, household
wall clocks are less accurate than they were back then.

Sylvia.

 

[Jeff Liebermann]

On Mon, 17 Aug 2009 19:22:09 -0700, David Nebenzahl
<nobody@but.us.chickens> wrote:

On 8/17/2009 6:44 PM Jeff Liebermann spake thus:

Got $10.70? Build your own:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=561-1014-ND

Interesting.

But once you've picked up WWV, what do you do with that signal to derive
a time base from it? (I guess you gots to know something about the
signal, which I don't.) Pretty simple?

Well, that's the basic receiver without that CPU. If you want to
build a complete receiver, methinks this one:
<http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=561-1016-ND>
is more appropriate. However it costs $71. The full development
system, with software costs about $250. I was thinking that it might
be best to have the PC do the processing, and use the cheaper
receiver.

I don't know that much about the code used by WWVB. (I are not a
programmist). I've gone as far as to disembowl an "atomic" clock
(cheap LCD display), and sniff the time signals with a scope. It
doesn't look too horrible. Some app notes on the CME8000 chip:
<http://www.c-max-time.com/downloads/search.php?search=CME8000>
Software flow chart:
<http://www.c-max-time.com/downloads/getFile.php?id=525>
Also, the demo board app note was misnamed. Download the file and
rename it with a .PDF extension. Then, it will be readable.

Start here:
<http://tf.nist.gov/stations/wwvb.htm>
<http://tf.nist.gov/timefreq/stations/radioclocks.htm>
<http://en.wikipedia.org/wiki/WWVB#Modulation_Format>
<http://en.wikipedia.org/wiki/Radio_clock>
Basically, you're building a clock, but instead of driving a display,
you're converting the UTC to something the PC will digest. There are
plenty of project on the internet, but none that I could find that
included PC interface software.

PIC Based WWVB Decoder
<http://www.geocities.com/hagtronics/wwvb.html>

Parallax Basic Stamp II Atomic Time Clock Receiver
<http://marwww.in2p3.fr/~levansuu/projets_es2i/Parallax/parallax%20website/stamps/atomictimeclock.htm>

Build a WWVB Radio Controlled Nixie Clock
<http://www.amug.org/~jthomas/wwvb.html>

Decoding WWVB from a Sony atomic time radio controlled clock
<http://leapsecond.com/pages/sony-wwvb/>

etc...


One more... WWVH on a ISA or PCI card:
<http://www.beaglesoft.com/clcahome.htm>

Research: Chip-scale atomic clock:
<http://tf.nist.gov/timefreq/ofm/smallclock/CSAC.html>

 

[Dave Plowman (News)]

In article <isw-0BB970.21153617082009@[216.168.3.50]>,
isw <isw@witzend.com> wrote:

Pretty much sums it up. But in those days few had dead accurate clocks
which are so common now.

Actually,they were very close.

Western Union clocks all over the country were almost always all synched
to within a second or so. The technique was to use clocks (those big
things with the red sweep hand you may have seen in a broadcast studio)
that were basically pretty good, and to synch them to a remote timebase
from time to time.

Oh indeed. Master clock systems were common once. But not in the home,
which is what I meant.

--
*Do they ever shut up on your planet?

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[Dave Plowman (News)]

In article <0002c59c$0$2257$c3e8da3@news.astraweb.com>,
Sylvia Else <sylvia@not.at.this.address> wrote:

In the UK, or in London at least, the mains frequency was maintained
with a very accurate long term average, so that synchronous mains clocks
just stayed correct.

The UK has had synchronised mains frequency for a very long time.

Sometimes, after short power cuts, the frequency was increased to bring
such clocks back to the correct time. Which was actually a bit of a
nuiscance for us - we had clocks that weren't self starting (a
reflection of the rareness of power outages in those days), so after a
power cut, we'd set the clocks correctly and start them, only to find
them gaining.

I can't remember the last power cut in this part of London. Many years ago.
Of course the household RCD has taken over that function. ;-)

It seems a backward step that now, forty or so years later, household
wall clocks are less accurate than they were back then.

'Radio' controlled ones are cheap these days.

--
*If Barbie is so popular, why do you have to buy her friends? *

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[Geoffrey S. Mendelson]

Jeff Liebermann wrote:

I don't know that much about the code used by WWVB. (I are not a
programmist).

It's a very simple system that is well documented. It's simple and slow
enough that anyone used to pulling apart data streams would be able to
decode it with a Z80 derived embedded processor, the ARM chips in dead iPods,
WiFi routers, etc would be "overkill".

Here in Jerusalem, we don't receive the signals of WWVB, or the German
or UK equivalents here. Someone about 50 miles north and out of the
mountains has a clock that syncs, but he never told me which station it
uses (he may not know), or how often it syncs. This lead me to research
how one would do the opposite, devise a local transmitter with an
ethernet port on one end for NTP sync and a 60kHz transmitter to sync a
clock on the other.

I gave up due to lack of a suitable design for the transmitter, no receiver
and a lack of funds to obtain them. You probably could do it out of one
of the Linux based routers, and blink one of the status LED's to generate
the 50/60kHz signal.

I know by now you must be thinking "why would anyone even think of such
a thing", but a discussion a few months ago about resurecting a Heathkit
Most Accurate Clock, got me going. I think I also read a posting that the
WWVB signals were being phased out.

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM

 

[Michael A. Terrell]

"Geoffrey S. Mendelson" wrote:

It's a very simple system that is well documented. It's simple and slow
enough that anyone used to pulling apart data streams would be able to
decode it with a Z80 derived embedded processor, the ARM chips in dead iPods,
WiFi routers, etc would be "overkill".

I did it 20 years ago with a VIC-20, in Commodore Basic.

Here in Jerusalem, we don't receive the signals of WWVB, or the German
or UK equivalents here. Someone about 50 miles north and out of the
mountains has a clock that syncs, but he never told me which station it
uses (he may not know), or how often it syncs. This lead me to research
how one would do the opposite, devise a local transmitter with an
ethernet port on one end for NTP sync and a 60kHz transmitter to sync a
clock on the other.

I gave up due to lack of a suitable design for the transmitter, no receiver
and a lack of funds to obtain them. You probably could do it out of one
of the Linux based routers, and blink one of the status LED's to generate
the 50/60kHz signal.

You need a good antenna system to transmit on 50 or 60 KHz. Here is
a sat photo of the WWVB antenna farm:


<http://maps.google.com/maps?hl=en&rls=com.microsoft:en-us&q=wwvb%20time%20signals%20ft%20collins&um=1&ie=UTF-8&sa=N&tab=wl>

I know by now you must be thinking "why would anyone even think of such
a thing", but a discussion a few months ago about resurecting a Heathkit
Most Accurate Clock, got me going. I think I also read a posting that the
WWVB signals were being phased out.

They replaced all the transmitters and towers at WWVB a few years ago
to improve service. It now reaches Central Florida without a long wire
antenna & tuner. Why would they spend millions and take a couple years
to do the update if they were planning to shut it down?


--
You can't have a sense of humor, if you have no sense!

 

[Jeff Liebermann]

On Tue, 18 Aug 2009 07:59:05 +0000 (UTC), "Geoffrey S. Mendelson"
<gsm@mendelson.com> wrote:

Jeff Liebermann wrote:
I don't know that much about the code used by WWVB. (I are not a
programmist).

It's a very simple system that is well documented. It's simple and slow
enough that anyone used to pulling apart data streams would be able to
decode it with a Z80 derived embedded processor, the ARM chips in dead iPods,
WiFi routers, etc would be "overkill".

Perhaps simple, not for me. I'm a lousy programmer and avoid
programming as much as possible. However, taking a closer look, it
does look rather simple.

Here in Jerusalem, we don't receive the signals of WWVB, or the German
or UK equivalents here. Someone about 50 miles north and out of the
mountains has a clock that syncs, but he never told me which station it
uses (he may not know), or how often it syncs.

See:
<http://en.wikipedia.org/wiki/Radio_clock>
There's a list of other LF time xmissions. I wouldn't give up trying
to hear various LF broadcasts. The problem is that they work best
late at night. From Israel, I would not expect to hear them with an
extremely short antenna. You may need to build a real LF antenna,
with proper matching circuit, and possibly a FET RF amplifier. Maybe
start with a loop antenna, which might be easier and grow as needed:
<http://www.febo.com/time-freq/wwvb/antenna/index.html>
<http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=350226240076>
<http://www.geocities.jp/bitalemon3000/english.html>

More on the C-Max receiver kit:
<http://www.prc68.com/I/Loop.shtml>

This lead me to research
how one would do the opposite, devise a local transmitter with an
ethernet port on one end for NTP sync and a 60kHz transmitter to sync a
clock on the other.

Building a store and forward repeater for WWVB (or the EU equivalent)
60Khz is a waste of time. The storage delay needed to regenerate the
signal will result in the sync pulses arriving too late. However, a
system that uses GPS, GLONASS, or Galileo as a reference, and
generates a simulated time code format will work. The problem is that
at 60Khz, the necessary antenna farm would be huge and the
transmitters rather power hungry. WWVB runs at an EIRP of about 70kW.

I gave up due to lack of a suitable design for the transmitter, no receiver
and a lack of funds to obtain them. You probably could do it out of one
of the Linux based routers, and blink one of the status LED's to generate
the 50/60kHz signal.

Starting with NTP, GPS, or a Cesium or Rubidium clock will work.
However, I don't know about the effectiveness of cramming it into the
limited abilities of a commodity router. Methinks you would be better
off with a SBC (single board computer) or common PC (ITX, Mini-ITX,
etc).

Actually, a 60KHz xmitter is fairly easy to design. The problem is
that all the components would be huge. There's also the not so easy
problem of getting Ministry of Communications approval. It's not on
the designated ham radio frequency list:
<http://www.moc.gov.il/sip_storage/FILES/0/390.pdf>
I'm sure that nearby users that went through the trouble of obtaining
large antennas, will not be thrilled with your transmissions. Even a
"local" transmitter can carry a substantial distance at 60KHz.

I know by now you must be thinking "why would anyone even think of such
a thing", but a discussion a few months ago about resurecting a Heathkit
Most Accurate Clock, got me going. I think I also read a posting that the
WWVB signals were being phased out.

The GC-1000 used WWV at 5,10, and 15 MHz, all of which are still on
the air. I'm not sure what a 60KHz system would do for you.

Repair your Heath kit GC-1000 Most Accurate Clock
<http://www.amug.org/~jthomas/gc1000.html>

I've given up asking "why". Some of the strange things I've seen on
the internet defy logic and explanation.



--
Jeff Liebermann jeffl@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]

On Mon, 17 Aug 2009 07:41:19 +0100, "Dave Plowman (News)"
<dave@davenoise.co.uk> wrote:

In article <4a88a59a$0$7469$822641b3@news.adtechcomputers.com>,
David Nebenzahl <nobody@but.us.chickens> wrote:
I agree that for most a minute per month is reasonable but I would
expect the same accuracy as my $29.99 Timex wristwatch which is more
like a second a month.

So that kinda begs the question of why computer mfrs. can't (or won't)
include clocks that are at *least* as accurate as a Timex, no? Wouldn't
a computah be a more compelling reason for a more accurate clock? (I
know, $$$ bottom line, right?)

Wonder if it's because a wrist watch is kept at a pretty constant
temperature via the skin?

Do you really expect people to wear a watch when they sleep just to
maintain accuracy? There's quite a difference in temperature between
skin temp (about 37C) and room temperature (about 25C). The same for
a computah. When turned off or in standby, the clock is slightly
above room temperature. When running, it might be as warm as 75C.



--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Geoffrey S. Mendelson]

Jeff Liebermann wrote:

Building a store and forward repeater for WWVB (or the EU equivalent)
60Khz is a waste of time. The storage delay needed to regenerate the
signal will result in the sync pulses arriving too late. However, a
system that uses GPS, GLONASS, or Galileo as a reference, and
generates a simulated time code format will work. The problem is that
at 60Khz, the necessary antenna farm would be huge and the
transmitters rather power hungry. WWVB runs at an EIRP of about 70kW.

That's sort of what I was thinking of. Get the time from NTP, generate
a fresh time code signal, which would not be accurate enough for someone who
wanted truely accurate time code, but to keep a clock that displays to the
minute, or even to the second on time, it would be good enough.

As for the transmitter, how much power do you need to transmit a signal from
a time code generator to a receiver next to it, connected via a coax cable?

A microwatt? A milliwatt?

limited abilities of a commodity router. Methinks you would be better
off with a SBC (single board computer) or common PC (ITX, Mini-ITX,
etc).

It depends. A cheap router, such as the Linksys WRTG-54L (note the L at the
end it's the enhanced model that runs Linux) would do it. It sells new for
not much money, will be obosolete as the 802.11N routers come into general
useage, has an ARM processor, two ethernet interfaces (one connected to a
4 port hub), a WiFi radio and a bunch of status LEDs. The advantage of it
is that there are several alternate Linux packages for it and you can easily
compile your own programs, build your own "flash" (firmware image) and load it.

There are also distributions for other routers, I recently bought a $30 EDIMAX
wired router that had a distribution for it.

Actually, a 60KHz xmitter is fairly easy to design. The problem is
that all the components would be huge. There's also the not so easy
problem of getting Ministry of Communications approval. It's not on
the designated ham radio frequency list:

If it is directly connected to the input of the receiver, it needs no
license.

I'm sure that nearby users that went through the trouble of obtaining
large antennas, will not be thrilled with your transmissions. Even a
"local" transmitter can carry a substantial distance at 60KHz.

I also expect there are none. Around here the noise level is so high that
they would never hear it until I got into the "real antenna" type system.
A microwatt with true isotropic radiator antenna (a short wire) would not
leave my apartment, let alone go anywhere. But if it is connected directly,
then it is a moot point.

I was thinking of something simple, such as flashing the LED at 60kHz, and
wrapping a pickup loop around it. That's about the same power level and
frequency of a TV remote control and no one from the MOC has come and
complained about any of the ones I have. I'm talking about the RF leakage
from it, not the optical signal.

The GC-1000 used WWV at 5,10, and 15 MHz, all of which are still on
the air. I'm not sure what a 60KHz system would do for you.

Not here. I have never heard them here, nor have I heard CHU (yes, I know it
moved), any of the European stations, etc. I'm not talking about a cheap
portable shortwave, I'm talking about a Kenwood R-5000 with a 75 foot random
wire, or other equally as sensitive ham receivers either with a 20m resonant
dipole or 1/4 wave vertical, or a 40m resonant dipole.

I'm not actually familar with the clock in question, the discussion (I think
it was on this newsgroup) focused on them using WWVB (VLF) radios.

I've given up asking "why". Some of the strange things I've seen on
the internet defy logic and explanation.

I'll agree with that.

Geoff.


--
Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM

 

[Geoffrey S. Mendelson]

Michael A. Terrell wrote:

They replaced all the transmitters and towers at WWVB a few years ago
to improve service. It now reaches Central Florida without a long wire
antenna & tuner. Why would they spend millions and take a couple years
to do the update if they were planning to shut it down?

They will shut it down eventually because of the cost. NTP servers cost
almost nothing, GPS is "free" because there are no incremental costs for
providing the time signals.

Eventually someone will figure out that a 75kW transmitter has both a
significant expense and a large "carbon footprint".

The upgrade was thought to be needed because of a satellite time system
that was dropped due to GPS was thought to be unable to fit the needs of
the common user. Now GPS units are almost throw away "toys", being used in
almost every cell phone, and for all sorts of SATNAV devices.

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM

 

[Arfa Daily]

"Dave Plowman (News)" <dave@davenoise.co.uk> wrote in message
news:508b196350dave@davenoise.co.uk...

In article <Xenhm.120546$zh1.31935@newsfe04.ams2>,
Arfa Daily <arfa.daily@ntlworld.com> wrote:

"Dave Plowman (News)" <dave@davenoise.co.uk> wrote in message
news:508ac7be38dave@davenoise.co.uk...
In article <Kfbhm.225069$xB.193120@newsfe10.ams2>,
Arfa Daily <arfa.daily@ntlworld.com> wrote:
And now that "The Bill" has got a 9 o'clock slot, they've changed the
shooting medium to something that looks altogether 'wrong',

It's called HD. ;-)

It's shot using progressive scan so you get the movement artifacts as on
film. Thompson (Grass Valley) cameras recorded on Panasonic P2 using
solid state memory cards.

Are you sure that's what it is ? Any HD that I've seen is just that. A
perfectly 'normal' looking picture, but with a higher resolution.

Trouble is they use fog filters on the cameras to reduce the resolution -
common on drama even in SD. And use long lenses most of the time to keep
the backgrounds soft.

Why should a higher res camera change the tonal composition of the
picture ? (assuming that it is being shot on video). Looks more like
they've changed from film to video, or the other way round perhaps.

No - it's always been video.

Or are maybe using a video mode that attempts to simulate film,
something like that. I saw it before on the programme when they did a
couple of 'specials'. Didn't like it then, don't like it now.

Tend to agree. But most production people hate video and will do anything
to make it look 'different'. They've also changed most if not all the
Lighting Directors. The Bill used to be known for using available light -
or making it look like it was. It now looks 'lit'.

rest snipped

So Dave, do you happen to know if "New Tricks" is shot available light ? I
was watching last week's episode that I had recorded, and that looked just
like "The Bill" used to. Do you also happen to know how Euston Films shot
"Minder" ? I watched an old episode of that on ITV4 tonight, and again, it
had a lovely 'untouched' look. Was that actually film, naturally lit, or
video ?

Arfa

 

[Michael A. Terrell]

"Geoffrey S. Mendelson" wrote:

Michael A. Terrell wrote:
They replaced all the transmitters and towers at WWVB a few years ago
to improve service. It now reaches Central Florida without a long wire
antenna & tuner. Why would they spend millions and take a couple years
to do the update if they were planning to shut it down?

They will shut it down eventually because of the cost. NTP servers cost
almost nothing, GPS is "free" because there are no incremental costs for
providing the time signals.

Eventually someone will figure out that a 75kW transmitter has both a
significant expense and a large "carbon footprint".

The receivers run on one or two AA cells for over a year. A GPS
system would use a lot more than 75 KW to power an equal number of GPS
based clocks.

The upgrade was thought to be needed because of a satellite time system
that was dropped due to GPS was thought to be unable to fit the needs of
the common user. Now GPS units are almost throw away "toys", being used in
almost every cell phone, and for all sorts of SATNAV devices.

Everything will die, some day including the earth itself.

Shutting down WWVB, with the large number of people using the 'Atomic
clocks' that sync to it would cause a real stink. You can buy 'Atomic
clocks' for under $20. Try replacing 75 cents worth of parts in a WWVB
receiver & decoder with a GPS based clock for the same price.

VLF can be received under water, as well. Try using GPS for a
submarine without surfacing, or raising a buoy with the antennas. Even
better, try using that floating buoy in rough waters.



--
You can't have a sense of humor, if you have no sense!

 

[isw]

In article <87pl851dui732j35j9oqki89ppqv79s2j3@4ax.com>,
Jeff Liebermann <jeffl@cruzio.com> wrote:

On Mon, 17 Aug 2009 07:41:19 +0100, "Dave Plowman (News)"
dave@davenoise.co.uk> wrote:

In article <4a88a59a$0$7469$822641b3@news.adtechcomputers.com>,
David Nebenzahl <nobody@but.us.chickens> wrote:
I agree that for most a minute per month is reasonable but I would
expect the same accuracy as my $29.99 Timex wristwatch which is more
like a second a month.

So that kinda begs the question of why computer mfrs. can't (or won't)
include clocks that are at *least* as accurate as a Timex, no? Wouldn't
a computah be a more compelling reason for a more accurate clock? (I
know, $$$ bottom line, right?)

Wonder if it's because a wrist watch is kept at a pretty constant
temperature via the skin?

Do you really expect people to wear a watch when they sleep just to
maintain accuracy? There's quite a difference in temperature between
skin temp (about 37C) and room temperature (about 25C). The same for
a computah. When turned off or in standby, the clock is slightly
above room temperature. When running, it might be as warm as 75C.

Yup, but the long-term average will be pretty good -- gain a little in
the daytime, lose a bit at night (or the other way around; could be
either one depending on how the circuit was set up).

Remember the old "Accutron" watches -- the ones with a tuning fork
inside? You could adjust those by deciding which way to lay them on the
table when you went to bed. "12 up" would run at a different rate than
"12 down" because of the effects o gravity on the fork. Also, they ran
noticeably fast on airplane trips, due to thinner air.

Isaac

 

[isw]

In article <6dnl859ciovp7fjjp5ec920cvos5gc2g6c@4ax.com>,
Jeff Liebermann <jeffl@cruzio.com> wrote:

-- snippage --

The GC-1000 used WWV at 5,10, and 15 MHz, all of which are still on
the air. I'm not sure what a 60KHz system would do for you.

Avoid a lot (but not all) of the problems caused by groundwave-skywave
conflicts that occur in the HF bands.

Isaac

 

[isw]

In article <slrnh8ltf5.4qg.gsm@cable.mendelson.com>,
"Geoffrey S. Mendelson" <gsm@mendelson.com> wrote:

Jeff Liebermann wrote:
Building a store and forward repeater for WWVB (or the EU equivalent)
60Khz is a waste of time. The storage delay needed to regenerate the
signal will result in the sync pulses arriving too late. However, a
system that uses GPS, GLONASS, or Galileo as a reference, and
generates a simulated time code format will work. The problem is that
at 60Khz, the necessary antenna farm would be huge and the
transmitters rather power hungry. WWVB runs at an EIRP of about 70kW.

That's sort of what I was thinking of. Get the time from NTP, generate
a fresh time code signal, which would not be accurate enough for someone who
wanted truely accurate time code, but to keep a clock that displays to the
minute, or even to the second on time, it would be good enough.

It would be *very good* because it would never drift. The rate
(long-term) would be spot on, and the epoch (the name for "what time is
it right now"?) would be only slightly in error.

As for the transmitter, how much power do you need to transmit a signal from
a time code generator to a receiver next to it, connected via a coax cable?

A microwatt? A milliwatt?

limited abilities of a commodity router. Methinks you would be better
off with a SBC (single board computer) or common PC (ITX, Mini-ITX,
etc).

It depends. A cheap router, such as the Linksys WRTG-54L (note the L at the
end it's the enhanced model that runs Linux) would do it. It sells new for
not much money, will be obosolete as the 802.11N routers come into general
useage, has an ARM processor, two ethernet interfaces (one connected to a
4 port hub), a WiFi radio and a bunch of status LEDs. The advantage of it
is that there are several alternate Linux packages for it and you can easily
compile your own programs, build your own "flash" (firmware image) and load
it.

There are also distributions for other routers, I recently bought a $30
EDIMAX
wired router that had a distribution for it.

Actually, a 60KHz xmitter is fairly easy to design. The problem is
that all the components would be huge.

You could synthesize the whole signal in software and drive a D-to-A
converter to create the modulated carrier. Any commodity video D-A would
be more than fast enough.

I'm sure that nearby users that went through the trouble of obtaining
large antennas, will not be thrilled with your transmissions. Even a
"local" transmitter can carry a substantial distance at 60KHz.

But very probably not, unless a very long antenna were attached to it.


Isaac

 

[isw]

In article <slrnh8ltf5.4qg.gsm@cable.mendelson.com>,
"Geoffrey S. Mendelson" <gsm@mendelson.com> wrote:

-- snippety-snip --

The GC-1000 used WWV at 5,10, and 15 MHz, all of which are still on
the air. I'm not sure what a 60KHz system would do for you.

Not here. I have never heard them here, nor have I heard CHU (yes, I know it
moved), any of the European stations, etc. I'm not talking about a cheap
portable shortwave, I'm talking about a Kenwood R-5000 with a 75 foot random
wire, or other equally as sensitive ham receivers either with a 20m resonant
dipole or 1/4 wave vertical, or a 40m resonant dipole.

But even the "best" receiver still wouldn't solve the multipath problems
that plague the MW bands.

Isaac

 

[Dave Plowman (News)]

In article <YmIim.201687$fS3.113178@newsfe05.ams2>,
Arfa Daily <arfa.daily@ntlworld.com> wrote:

So Dave, do you happen to know if "New Tricks" is shot available light ?
Not sure.

I was watching last week's episode that I had recorded, and that looked
just like "The Bill" used to. Do you also happen to know how Euston
Films shot "Minder" ? I watched an old episode of that on ITV4 tonight,
and again, it had a lovely 'untouched' look. Was that actually film,
naturally lit, or video ?

Euston Films never used video. Suitable location equipment simply wasn't
available in those days. They mostly used 16mm - with some 8mm if they
wanted a particular effect.

I should make clear that making something look like it's shot by available
light doesn't mean actually doing just that. Reflectors and flags etc are
used to reduce the contrast to acceptable limits. To do it well can be
more time consuming than actually lighting the thing. ;-) But things like
Minder from Euston films were shot at breakneck speeds in normal film
terms. ;-)

--
*If a pig loses its voice, is it disgruntled?

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.