[time-nuts] Building a GPSDO & trouble using Jupiter-T

Hal Murray hmurray at megapathdsl.net
Sun Jan 29 23:40:52 EST 2012

> What do you mean by "average"?  Do you mean that the GPS and PLL must be
> kept on for "20 minutes to hours", or did you mean that the PLL loop filter
> must have a time constant of 20 minutes to several hours?

You have to compare the characteristics of the oscillator with the 
characteristics of your GPS receiver.

If your local oscillator is very stable, then you want to average over long 
times (hours, days).  If your local oscillator is a good thermometer and you 
have a very good GPS receiver, then you want a shorter time constant 
(minutes) so you can track temperature changes.

Do you know about hanging bridges?  If not, please read Timing for VLBI by 
Tom Clark and Rick Hambly.  It's got some wonderful graphs.  Once you 
understand those, this discussion will get much more interesting.

These are my opinions, not necessarily my employer's.  I hate spam.

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