How to set the time of DOLBY DSS200 server to correct time?

[Marcel Birgelen]

What NTP server are you using?! The whole idea is to keep your DCI gear connected to an NTP server AT ALL TIMES, because the internal clock isn't sufficient reliable over the long run...

[Randy Stankey]

I don't know about where you are located but here, where I live, I use a time server operated by the U.S. Naval Observatory.
tick.usno.navy.mil or tock.usno.navy.mil (Get it? "tick" and "tock"? )

Your profile says you are in China so my server is probably restricted for you. A time server located in the United States won't do you much good, anyhow. You need to find a time server located in China.

I'm certain that the government of China or some-such public entity operates time servers that you can use where you live.

Every computer, iPhone or other device that I own which can use a time server is set for "tick" or "tock."

Never had a problem getting accurate time in years.

[Marcel Birgelen]

Your profile says you are in China so my server is probably restricted for you. A time server located in the United States won't do you much good, anyhow. You need to find a time server located in China.

Why not? Is China now also censoring the time? Time servers keep their time in UTC, your system is responsible to convert it into the local government's sanctioned time-zone.

What's important for NTP to operate is a low-jitter on the connection to the NTP server, the latency itself is far less important. But usually, with greater latency usually also comes greater jitter. That's why choosing a local NTP server is usually a wise thing to do, also this keeps local traffic local.

[Randy Stankey]

I was under the impression that Tick and Tock were restricted to the eastern US. If you are in the left half of the country, you're supposed to use the NIST servers in Colorado. Aren't you?

Then, I thought that, if the US Govt. restricts the use of its time servers, other countries like China would likely do the same.

Like you say, it's best to use a time server that is close to your location and that's another reason why I suggested using a Chinese server.

Does the government censor time? Yeah, sort of...
Did you know that the United States' GPS system can be programmed to introduce random errors in location by up to 10 km?
It's only supposed to be used in times of war so that an enemy can't use our own technology to attack us but the govt. has turned that "feature" on, from time to time, in the past.

I believe, if memory serves, that President Clinton signed a law that says that they aren't supposed to be allowed to do that, anymore unless there is a compelling reason like war.

Point, here, is that, if the United States can do things like that, it's a sure bet that other countries, China inclusive, can also do it.

Do you think that all the time servers and GPS satellites in Russia are always in perfect sync? (Whatever the Russians call their satellite navigation systems.)

I wouldn't bet on it. Especially not right now!

BTW: Here's a list of available time servers that people can use, classified by location/country.

https://support.ntp.org/bin/view/Ser...OneTimeServers

While I'm sure that this is an authoritative list, I still suggest due diligence to be sure that you can use a particular server before setting your computers to sync with it.

[Marcel Birgelen]

The highest resolution time signal for all three "geo-positioning systems" are encrypted and only for military use. Instead of adding randomness to GPS and causing all kinds of wonky situations for stuff like satnav, it's more common to simply disable it, but the intention to do that has since become less appealing as there are often two competing systems available, the Russian GLONASS system and the European Galileo system. Many modern mobile phones support all three of those systems and average results of those systems to increase accuracy. And I do believe those systems are almost always perfect in sync, because they would otherwise not work correctly

Also, the NTP protocol is designed to be a tiered setup. You're more or less supposed to have multiple NTP servers as source. NTP serves that are too far away from the baseline will simply be ignored, that way, NTP roots out iffy NTP servers.

[Carsten Kurz]

The intentionally introduced clock errors on the existing satellite navigation systems are there to introduce location, not time errors. The timing error to introduce a major location uncertainty are minute compared to time errors we as humans would notice. So, even if SA or even greater errors would be reintroduced as temporary security measures, the resulting timing errors were extremely small and would never cause any issues with common timekeeping systems (except maybe such for high security transactions, encryption, or scientific experiments/research).

As long as Selective Availability was active on the GPS system (until May 2000), the resulting location error was around 120m, the timing error was in the 100ns (nanosecond) range. That's 0.1 microseconds. A stratum 1 timeserver typically is accurate to 10 microseconds. So, even under Selective Availability, achievable GPS derived time was 100 times more accurate than necessary for Stratum 1 time servers.

[Randy Stankey]

I understand about Selective Availability and encryption on the GPS system. I don't know a lot about the Russian and European systems but I assume that they work in a similar way and have similar features.

When I mentioned that the GPS system can have intentionally introduced errors, I was referring to something I read in a book by Bob Berman, professional astronomer and science writer. He explained how the system works and how they account for relativistic effects. In that section, Berman explained about intentional errors and why. He also said that because GPS is used by commerce and science, Clinton signed a bill to stop doing that. (Probably inside some sort of omnibus bill.)

The question was whether governments ever censor or intentionally alter time data or other such things.
The short answer is, "Yes, they can, via methods we all described, above."

Have they done it? Yes they have, in the past."

Do they do it now? Probably not. Clinton's paperwork says so. There's too much money riding on it.

Will they do it in the future? Not likely unless there's a compelling reason like war but, as with much that has to do with government, we can never really know for sure.

I don't think I'm being conspiratorial. Just pragmatic.

If there ever was another world war, we might want the government to shut down the GPS system or, somehow disable it so that only people we want can use it and so that our enemies can't use our own technology against us.

[Carsten Kurz]

USAF has developed other means to control GPS. Latest GPS satellites have beam steering antennas, so they can disable, degrade, or spoof GPS or parts of the GPS signals completely for certain geographic areas and not globally if needed, without impacting their own military use in the same area. Also, how much sense does it make to limit GPS accuracy if there are three other competing systems with global coverage which are out of control of the USAF? Galileo, GLONASS, and BeiDou all offer basically the same navigation and timing performance, and everyone can buy quad-system receivers for a few bucks now or has them already in their smartphone.


'The United States has no intent to ever use Selective Availability again.'

https://www.gps.gov/systems/gps/modernization/sa/


The civil use of GPS has become so important that it simply has become completely undesirable to limit it. Also, because of the threat of Selective Availability and performance limitation essentially did encourage other countries to build their own systems. SA worked as long as other countries were not able to create their own satellite based navigation systems. It has become useless now.

[Randy Stankey]

That's pretty cool! I was, just last week, reading about phased emitter arrays and how they can be used for beam steering. It's pretty damned amazing stuff!

Think about it... GPS satellite works in the 1,500 MHz range. Phased antenna arrays will vary the frequency of each element by 1/4 wavelength and the timing between elements must be very, very precisely controlled in order to achieve the beam steering effect. That means that the electronics inside a GPS satellite have to be accurate and precise to a range that is less than 0.00000015 seconds! (Thumbnail math. I'm too lazy to grab a calculator. )

A few years ago, I was working at another electronics shop when I was assigned to work on hand assembling some strange looking circuit boards. Nobody seemed to know what they were for. It took a couple of weeks to complete the order. During that time, I sat there, working and looking at the traces on the back of the boards. The traces were three large arcs in a zig-zag pattern and there was a dull, black coating on them. It finally dawned on me... Position sensors! The boards were basically giant potentiometers and moving the wiper arms allowed some device to determine angles.

The supervisor showed me the work order and it said that the customer made antennas and equipment for cellular phone towers, etc. We looked at the CDG and deduced that these boards were position sensors for cellular antennas. They allowed the antennas to swivel and change position in order to tune the performance of the cellular tower.

Pretty much, the supervisor, the production engineer and myself were the only people in the shop who understood how cool this was.

For me, that kind of assembly line work is drudgery. Dull and boring. It makes it a lot more fun to do my job when I know a little something about the things I'm working on. Alas! 90% of the people working in these shops just sit there and do monkey work with little understanding of what they are actually making.

It pisses me off when I have to do things like explain to my process trainer about tinning the ends on connector pins, how it works and why we do it!

Anyway... I'm kind of glad that we have three or four different GPS satellite systems. GPS and precise time have become (or are becoming) like public utilities, no less important than sewer, water and electricity. The problem is that if GPS breaks, you can't just climb a pole and fix the wires like you can when there is a power outage. Having multiple systems in place gives redundancy that might be needed. If something goes wrong with one system, we have backups that can be used until things get ironed out.

[Mark Gulbrandsen]

I have had GPS time receivers in my home for over 20 years, mainly because of my interest in clocks, but also to use as a calibration reference.. I am on my third one now, all due to changes in the GPS protocol... the last one due to an existing bug in the day that was sent out by the Satellites. This bug was known to exist and it did not affect all receivers. . All had or have rubidium oscillators in them so I can calibrate electronic gear to a very stable know reference.

The four pictures are of old receivers.

1. A Datum GPS receiver from Trinity site feeding a Datum Time Code Reader. The time code reader has a gazillion IC's in it!! When I got the Datum is was 16 years old and eventually succumbed to the rollover issue. It still reads perfect time though and because of where it's from I am keeping it.

2. An Efratom GPS locked receiver containing twin rubidium oscillators. There were two in case one oscillator failed, it would switch over to the backup.

3. Inside the Datum, it was full of Trinity site sand. Not sure if it's radio active or not and don't really want to know.

4. Display on the Datum. The receiver is still stabilizing..


Also, This link may interest some of you: https://www.gps.gov/cgsic/meetings/2017/powers.pdf

[Randy Stankey]

... it was full of Trinity site sand. Not sure if it's radio active or not and don't really want to know. ...

Carefully clean up the sand, put it in a metal coffee can, fill it with concrete and embed a penny with this year's date in the surface then bury the can in the back yard as deep as you can dig with a shovel.

Or, better yet, bury it in the middle of nowhere.

[Mark Gulbrandsen]

LOL! I took it all apart and blew the sand out with compressed air... That was over ten years ago., So if any of it is blowing around it is in Utah and now I'm in Tennessee... so, a safe distance from it I think.

[Randy Stankey]

Years ago, I knew somebody who pulled apart a smoke detector. I was like, "Dude! That's Americium in there! It's radioactive for 10,000 years!"

That's when I conceived the coffee can idea. It was either that or call the fire department or other authorities which might set off all kinds of alarm bells.

The penny embedded in the concrete is there to give anybody who finds it, in the future, some idea of how long it had been there.

I don't remember how radioactive Americium really is or what type or radiation it emits. I suppose I could look it up.
The whole reason for the exercise was because if the authorities found out, there would be questions asked and cleanup costs to pay.

Americium really isn't THAT dangerous or else they wouldn't put it in smoke detectors for sale to the public.

I just wanted to make the problem "go away" as quietly and as safely as I knew how.

[Stefan Scholz]

There are situations, where there is no access to a NTP server. I serviced 2 drive ins, and in both, the projectors were controlled locally without any networked connection. One lost it's time frequently, and the solution at the end has been to connect a WiFi bridge, use the operator's smartphone as a source for the NTP, by connecting over wifi to a phone provided hotspot every day at startup. That solved the problem, and the time was kept in sync with actual time.
AS stated by others here, DCI timekeeping relies on true NTP server synchronization.

[Marcel Birgelen]

That's pretty cool! I was, just last week, reading about phased emitter arrays and how they can be used for beam steering. It's pretty damned amazing stuff!

Well, GPS is a relatively simple signal... imagine this being done for a broadband Internet connection... I guess that's why Musk is paying about $1500 on top of every StarLink terminal they're selling.

I have had GPS time receivers in my home for over 20 years, mainly because of my interest in clocks, but also to use as a calibration reference.. I am on my third one now, all due to changes in the GPS protocol... the last one due to an existing bug in the day that was sent out by the Satellites. This bug was known to exist and it did not affect all receivers. . All had or have rubidium oscillators in them so I can calibrate electronic gear to a very stable know reference.

We used to have a bunch of these at one of my previous jobs, located in several datacenters throughout the world. From those, we fed our own Stratum 2 NTP servers, which were then used by all the different clients. If you're stuck somewhere without reliable Internet access, there are cheap alternatives nowadays, like a RasPi-based NTP server, that syncs with GPS.

Nowadays, my primary time reference is provided by this guy, I mean, he runs several cesium atomic clocks, some kept on UTC and others on TAI time. Personally, I'd really love to switch all machines to TAI time to get rid of those damn leap seconds, which have often caused havoc in complex computing systems that require precision timing and don't like to see the same timestamp twice...