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

David Kirkby david.kirkby at onetel.net
Thu Jul 7 09:06:36 EDT 2005

Javier wrote:
> Hello,
> 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.
> Regards,
> Javier, EA1CRB

Is turning off the 1pps, the best thing to do if controlling a crystal 
or rubidium? It seems most logical to me, so I can't understand why the 
default is to not to.

David Kirkby

> 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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David Kirkby,

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