![]() UT1 was known as GMT (Greenwich Mean Time) before the ISO standards, but that term is obsolete. But the Earth wobbles and gives small random fluctuations in its rotation. The UTC is based on an atomic clock, which is very stable and consistent. The world runs on two clocks, UTC (Coordinated Universal Time) and UT1 (mean solar time-observed Earth rotation). This means that you might have a minute with 59, 60, or 61 seconds in duration. To keep the official atomic clock for the world and the astronomical clock aligned, we created a “leap second” to adjust them. Second are shown as two digits between “00” and “59,” mostly. Joe Celko, in Joe Celko's Data, Measurements and Standards in SQL, 2010 7.1.5.3. ![]() However, while being generally sound and an improvement over not adjusting for network delay, there are still three sources of error with this technique that can affect the accuracy of the d/2 delay assumption: (1) Network delays are time-varying (2) network delays can be different in each direction, even on the same link and (3) the processing delay on each computer is also time-varying. This halved value can thus be added as an offset when sending the time stamp so that when it arrives, having suffered the equivalent delay, it is realigned with wall-clock time, and thus, the recipient can set its clock accurately. ![]() Therefore, the assumption is that if the total delay is halved, then this is representative of the delay in one direction. This approach uses the same clock to measure the start time and end time of the round trip this is the clock of host X in the figure, hence avoiding any inaccuracies arising from the fact that the clocks are not yet synchronized. The concept is simple: measure the round-trip time for a message to be sent to another computer and a reply to be sent back this takes into account the delay in each direction in the network and also the processing delay at the two computers themselves when dealing with sending and receiving the messages. Cristian's algorithm for physical clock synchronization.įigure 6.22 shows the principle of estimating network delay used in Cristian's algorithm. You can resize it, move it around, when you restart your PC it comes alive in the last place it was left when you turned your PC off and best of all it's free! Have a look at it and see what you think and by all means if you are using another program let me know what it is and I will check it out.Figure 6.22. It occurred to me to get online and search for something that was a free download on the internet!! I found a neat little program that sits on your desktop. I was going to purchase the MFJ 108B dual LED clock but it was good I held off. The same issue comes up when logging a contact on paper temporally until logging it on the PC. As I was attempting to ferret out the contest an old issue came back to me.UTC time! I have an app on my Iphone that gives local and UTC time but more often than not the Iphone is not close by when I need to reference UTC time. To be honest I did not have to much luck with either, I really could not make out the exchanges and the web site was not really clear what contest this could had been. I went to WA7BNM contest site and looked things over to see what contest it was while at the same time listening to the contest to see what the exchange was. Then at 1700 UTC I was listening on 20m and on the Elecraft P3 the lower end of 20m came alive! From only hearing U.S stations to hearing LOTS of European stations and at first I could not tell if it was a contest or not but it had to be. I was going from band to band around 1600 UTC and there was just stations here and there most U.S stations. I have Friday off today and got my running around out of the way this morning, so I decided to flip the radio switch and see what was happening.
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