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[linrad] Re: beta-MAP65 using
- Subject: [linrad] Re: beta-MAP65 using
- From: Rick Kunath <charter.net; k9ao@xxxxxxxxxxxxxxxx>
- Date: Sat, 07 Jul 2007 10:56:30 -0400
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
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
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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