[time-nuts] 1pps signal presence with no GPS signal.

Javier javier at nebulosa.org
Thu Jul 7 05:46:01 EDT 2005


The 1pps signal on a M12+ is switchable. It can be selected to be on all 
time or on only when tracking at least one satellite.


Javier, EA1CRB

David Kirkby wrote:

> I have a Synergy GPS unit, which is fitted with a Motorola M12+ 
> receiver. Even if there is no signal (even no antenna connected) the 
> 1pps light flashes on the front and there is a 1pps signal at the 
> output connector.
> It would seem to me that if you lock a crystal/rubidium or whatever to 
> a GPS system, the last thing you want to do is to steer your source 
> from a 1pps signal that must be pretty inaccurate. I assume this gets 
> derived from the uncompensated crystal oscillator on the Motorola 
> board, and so is far less accurate than the source you are phase 
> locking to it.
> I would have thought it more sensible to cease the 1pps signal as soon 
> as a GPS is not locked to at least one satellite.
> Comments?

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