[time-nuts] 1pps signal presence with no GPS signal.
david.kirkby at onetel.net
Thu Jul 7 09:06:36 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
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 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.
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