[time-nuts] NTP apps on Windows question

[Martin Burnicki]

Chris Wilson wrote:
> I have used Meinberg NTP ...

It's important to keep in mind that the NTP software for Windows has not
been written by Meinberg. It's just the reference implementation of the
NTP protocol provided by the NTP project at
http://www.ntp.org

Releases are normally available as source code only at the NTP community
pages at
https://support.ntp.org

We at Meinberg support the NTP project by sponsoring, testing,
submitting bug reports, and eventually providing patches. We also pick
up the source code releases, build the binaries for Windows, provide
them with a cryptographic signature, and put them into a GUI
installer/setup program to simplify installation under Windows:
https://www.meinbergglobal.com/english/sw/ntp.htm#ntp_stable

> ... and also Thinking Man's Dimension 4 as NTP
> applications on Windows 7 64 bit OS's on 3 PC's. I use them to sync
> the PC time for WSJT-X WSPR (a low power digital amateur radio mode)
> which requires an accurate time on the PC's for successful decoding
> and transmitting of digital signals.
> 
> Both Dimension 4 and Meinberg have occasionally not allowed proper
> syncing with the WSPR application attempting to decode up to 4 seconds
> late, despite my Trimble Thunderbolt and Lady Heather showing the PC
> is synced to GPS time within less than a second, by eye.

Hm, it would have been interesting to find out *why* this didn't work.
Normally, ntpd considers a time offset that exceeds 128 ms so huge that
it steps the system time.

If the time offset is below this limit the Windows system time is slowly
slewed so that the offset becomes (and continuously stays) as small as
possible. This slewing is normally not even noticeable for applications.

However, this only works properly if there is no other tool that fiddles
with the system time. If you change the system time manually, or another
program sets the system time periodically then ntpd will be unable to
compensate this quickly.

BTW, running Microsoft's w32time and ntpd together will not work
properly since both programs try to use network port 123 at the same
time, which is not possible. This is why the NTP installer disables the
w32time service by default when ntpd is installed.

Please note that in the past there have been lots of problems with
accurate timekeeping, depending on the Windows version. Usually this was
due to limitations in Windows.

For example, some years ago there were some kernel drivers which caused
the Windows kernel to loose time. In another case the Windows system
time was off by about 30 seconds whenever a big database application had
run some maintenance task in the night.

The fact that 2 different software packages showed similar errors makes
me assume that

- time sources were not reachable, or
- system time was changed by a different application, or
- there is some program that unintentionally affects the system time

> I am now trying another NTP app by DL4YHF Wolfgang Buscher. My
> questions are, is such an anomaly known and should I disable Windows
> Internet Time synchronization when using another NTP app? I see no
> mention of disabling this in any of the NTP application's notes... The
> WSPR application, WSJT-X has very recently been released in a 64 bit
> version, which is what I am using, and I have to wonder if the new
> version has some minor bug as I find it hard to believe two well known
> and used NTP apps are buggy.

As already mentioned in other replies, you should *never* have 2
applications running at the same time that try to adjust the system time.

Martin (working @Meinberg)