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[linrad] Re: beta-MAP65 using

Comments below quoted text...


As it is now, it is important that BOTH computers have their clocks set to the correct time, within a second or so. I do this by starting Linrad with a short script that first executes "ntpdate", then xlinrad.


Of course, the value will depend on clock settings on one or both of your computers (I think it is only the Linrad computer, at present), and also on the transmitting station's clock setting.


2) syncronize the time from a PC to the other so that they have lined up perfectly or ignore the time sent from Linrad completely.


I will think about this one. As I mentioned, at present I run ntpdate on the Linrad computer just before starting Linrad. On the MAP65 computer I run Dimension 4. I will probably put second ethernet cards into each computer so that the Linrad -> MAP65 connection has a dedicated line; then each computer can have good access to the internet, as well, and keep its own clock set accurately.

I am wondering why on the Linux machine you didn't just run the NTP daemon? I've been using that method for years and it works extremely well. Using the NTP daemon would allow for even better accuracy of the clock on the Linux machine than just doing an ntpdate prior to running xLinrad.

You generally configure NTP to use at least 3 local (geographically) time servers, accessible from the Internet. As a part of NTP, these are evaluated for the best accuracy at startup, then the best one (dynamically checked at regular intervals) is used for motherboard clock synchronization.

As NTP runs, it will develop a motherboard clock drift value that it will use to predict and compensate for motherboard clock drift and accuracy, allowing for better time accuracy than you could get with the motherboard clock alone. The multiple time servers allow for redundancy and allow NTP to constantly choose and synchronize with the external time server that has the least delay and jitter at the moment.

Usually as NTP starts, it uses a time server in the step-tickers file to kick the motherboard clock to the correct tine on booting, then starts the NTP daemon to do the rest. After a few minutes, it will settle down and long-term accuracy is outstanding. There really isn't anything one has to do once it is setup, it just runs in the background.

watch ntpq -pn as root will allow you to see the action as NTP evaluates and syncs with the external time servers then selects the best one.

NTP can also serve time to the built-in Windows OS network time function, just as a Windows domain controller would, so you can use the NTP on the Linux machine to synchronize the Windows machine. If you decide to do this, you'll need to allow the internal Windows (or other OS) machine to connect to the Linux machine's NTP server for synchronization. This is generally disabled as you don't want other users out in Internet-land connecting for sync purposes. You can easily allow for your local LAN to use the machine for NTP time synchronization while blocking everything external to it else in the ntp.conf file settings.

I just thought I'd pass this along as I don't know if you have considered it. Any recent distro can set this up easily, You'll just need a simple tweak for local tine serving, and to add the network-time config to the Windows machine built-in network-time function.

I've been using this scheme for years on mixed Linux, Solaris, and Windows networks and it works nicely.

Windows does not have the same time accuracy capabilities of the Linux and other *nix operating systems using NTP, but it will still allow for extremely accurate synchronization of time. Maybe someone knows of a better way to use a Linux machine to sync a Windows machine using the Linux NTP than the built-in Windows network-time application?

If you have a local GPS or GPS-trimmed Rubidium high-accuracy time standard with NTP serving capability, Linux NTP can be used to sync to this, and use Internet time servers as a backup. I use this setup one one of my networks.

Rick Kunath, k9ao

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