[time-nuts] Jupiter modules: 1pps or 10kHz to lock an OCXO ?
quenbob5 at pacbell.net
Mon Dec 22 02:33:49 UTC 2008
I thought of something else. Time to lock can be really long. Say the OCXO
can swing +/- 1 ppm, +/- 10 Hz at 10 MHz. The +/- 1 ppm also applies to 0.5
Hz. To swing 180 degrees at 0.5 Hz, assuming the low pass filtered control
signal pushes the OCXO the full 1 ppm, will take 1e6 seconds unless you use
a circuit similar to what I used to prealign 50 Hz signals in the 100 Hz
Motorola Oncore design.
----- Original Message -----
From: "Patrick Reynaert" <preynaert at yahoo.com>
To: "time-nuts" <time-nuts at febo.com>
Sent: Sunday, December 21, 2008 2:13 PM
Subject: [time-nuts] Jupiter modules: 1pps or 10kHz to lock an OCXO ?
> Using the 10kHz output to lock an OCXO is common practice and seems to
> give good results.
> Has anyone tried to use the 1pps output? One? could first make a simple
> divider to create a 0.5Hz reference with 50% duty cycle, and then use this
> signal to lock an OCXO. This would also allow the use of other OEM GPS
> modules that don't have the 10kHz but only the 1pps signal.
> Of course, as the 0.5Hz signal is much lower in frequency than 10kHz, the
> short-term stability is pushed more to the OCXO, making the requirements
> of the OCXO even harder.
> But maybe the 1pps signal has better stability than the 10kHz signal? Or
> is this the same since these signals will only influence the long-term
> stability of the oscillator and have the same accuracy?
> Any thoughts are highly appreciated.
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