[time-nuts] GPSDO Question
GandalfG8 at aol.com
GandalfG8 at aol.com
Sun Sep 2 19:10:24 EDT 2007
In a message dated 02/09/2007 04:20:54 GMT Daylight Time,
bruce.griffiths at xtra.co.nz writes:
It is amusing/distressing to see that the myth that using an FLL to lock
an oscillator to the PPS output of a GPS receiver is a good approach
still persists.
The optimum solution is a phase lock loop.
Whilst building an FLL is instructive/educational, if you want the best
GPSDO performance you should really use a PLL.
--------------------
Perhaps it depends on how you define a "good" approach.
If you're looking for the very best you can get then it probably isn't, but
I don't recall that being claimed in the first place.
However, one of the attractions has to be the simplicity of the circuit and
the fact that something offering reasonable performance can be knocked up
very quickly.
Without the divider and buffers, the circuit proposed by Bertrand Zauhar,
VE2ZAZ, in his QEX article reduces to just three ICs.
It may not be optimum but it must be a strong contender for the best you can
get for very little effort.
The Idaho State University version is reported on their web page for the
project as having been checked over a 13 day period, by the Idaho National
Laboratories Calibration Lab, and found to be accurate to 1.2x10^-10.
I don't think that's too bad for a fun project that could probably be put
together in an evening, even for one guilty of causing such amusement and/or
distress:-)
regards
Nigel
GM8PZR
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