-----Original Message-----
From: main@WSJTX.groups.io <main@WSJTX.groups.io> On Behalf Of Martin G0HDB
Sent: Thursday, June 2, 2022 2:21 PM
To: main@WSJTX.groups.io
Subject: Re: [WSJTX] Meinberg Error #Timesync

On Thu, Jun 2, 2022 at 06:19 PM, Reino Talarmo wrote:

Hi Art,

Just a minor correction. NetTime does not provide the same
functionality as Meinberg or any other program that supports full NTP protocol.

Extract from Accuracy Notes:
The vast majority of users should find that NetTime more than meets
their needs, however if you have specific requirements for very
accurate time, I recommend that you investigate installing a full NTP
client. Although you can set NetTime to sync more frequently to
compensate for an inaccurate system clock, this isn't really
recommended because of the greater strain that it puts onto the public
NTP servers. A full NTP client has extra features to ensure better
time accuracy (normally well below 10 milliseconds even between time syncs) by adjusting the rate that the system clock runs at.

Hi Reino (and all), one factor that shouldn't be overlooked when deciding which time-sync'ing app to use on a PC is the effect of using an app such as D4 (and also NetTime?) that is based on the SNTP protocol rather than the full NTP protocol implemented by the Meinberg app.

An SNTP app doesn't adjust the clock smoothly, as the Meinberg app does, but can cause step-changes (in either direction); the effect of these is described perfectly and succinctly by the late, much-missed Bill Somerville G4WJS:

"What is sure is that a step adjustment to the PC clock during a receive period will cause an audio stream discontinuity, and that in turn may disrupt all decoding for that period. "

In other words, if you use an SNTP-based app then you can expect to suffer from missed decodes in any Rx period in which a step-change of the PC clock occurs. This missed-decode effect has been observed and verified in practice.

73
--
Martin G0HDB








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