locked Re: "Dimension 4"

Bill Somerville

On 26/10/2020 12:17, Ron W3RJW via groups.io wrote:

The latest version of D4 (5.31) will run on Win 8.1 and earlier. Doesn't claim to run on Win 10?? It's fully automatic, updating the system clock at your specified interval with user specified time server data.  Seems to work as well as any other time sync program I've tried.

while your information about the automatic operation of the Dimension 4 time synchronization utility is correct it is only a basic solution to this problem. You comment illustrates that as it is an SNTP time service client and as such only adjusts the PC time by periodically brute-force stepping of the clock. For many applications that is OK and if your PC keeps reasonably good time without any synchronization you may never see any issue. This is not the case for all users. There are full NTP implementations that will adjust the rate of the PC clock by characterizing it compared to a reference time servers known to be accurate. As such it is possible for an NTP implementation to guarantee that, after any start up adjustments, the clock is monotonic, which means there are no backward or forwards steps over clock ticks and every tick happens in their implicit order. A monotonic clock is important for real-time audio applications like WSJT-X since discontinuities introduced into sample streams, ultimately caused by clock adjustments, are likely to disrupt decoding of signals.

The net effect of the above is that we no longer recommend SNTP time synchronization tools. No doubt many users of Dimension 4 and other SNTP tools will say that they have no issues and will continue to use them, perhaps not knowing or caring that occasional failures to decode a receive period may have been due to a time step.

On Windows we have verified that the free Meinberg NTP Client, and, a low cost sync tool that can easily use a GPS time source NmeaTime2, are able to characterize an discipline a Windows PC clock without steps (with some caveats). On other platforms a suitable NTP implementation is usually installed and enabled by default if Internet time synchronization is enabled. Note that the Windows Internet Time sync tool w32tm is a full NTP implementation but by default is configured to only check time at large intervals which causes it to make steps. Configured with default settings w32tm is effectively a low accuracy SNTP tool.


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