[time-nuts] simple, cheap clock for the local LAN

Bob Camp lists at rtty.us
Tue Apr 6 12:27:06 EDT 2010


The question always is - Am I more likely to loose GPS or loose power?

Other that random bird attacks, a GPS with a proper outdoor antenna is
pretty reliable. With a rational indoor antenna and a modern receiver,
dropouts are normally brief, if they occur at all. 

Power has an odd habit of going out soon after bar closing time on Saturday
night. If power is out for more than ten or twenty minutes, I have no need
for time on the local LAN - the backups on the switches and other gear drop
out pretty fast.


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Mark Sims
Sent: Monday, April 05, 2010 1:18 PM
To: time-nuts at febo.com
Subject: [time-nuts] simple, cheap clock for the local LAN

Just use everybody's favorite GPSDO,  the Thunderbolt.  While it is being
disciplined by GPS,  it is learning how the oscillator tends to age with
time and drift with temperature.  If GPS goes away,  it will still
discipline the oscillator in an "open loop" fashion using its learned
behavior.  The HP GPSDOs do the same thing.

Lady Heather has an option for periodically syncing the system clock to
Tbolt Time.  At its most agressive setting,  it keeps the system clock
within a windows timer tick (20-50 msec).

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