[time-nuts] GPS interference and history...

[Chris Albertson]

On Fri, Jan 13, 2012 at 6:29 AM, Jim Lux <jimlux at earthlink.net> wrote:

> I suppose one could use some sort of GPRS cellular service and get time, but
> then you're on the hook for a monthly subscription fee, etc.

They sell such devices.  They don't require a subscription because
they are receive-only.  You don't need to send data to get time.    I
don't know about GPRS, but there have been commercial CDMA time
receivers on the market for years.   People who don't have access to
the sky but do get cell phone service buy them.  For example you are
on the 14th floor of a 50 floor office building and your window faces
another building.   That is the biggest problem with GPS, you need
access to the sky.
>
> cheap L1 only GPS is a great solution.  Apply power, wait, you've got
> accurate time.  No need to have someone visit periodically and check to see
> if the clock needs to be reset, etc.
>
>
>
>
>>
>> I'm not sure why they need GPS at the recording house.  They know where it
>> is
>> so timing is the only use I can think of.  But they could also get that at
>> the receiving end.  Millisecond accuracy isn't helpful.  Second level
>> accuracy might be interesting if something breaks and you want to know
>> when
>> the wave got to downstream stations.  The risetime is probably over a
>> second.
>>
>>
> You're right, they don't need milliseconds, nor do they need seconds,
> probably.
>
> There's really no other convenient way to get time to the nearest minute
> that is as reliable and cheap as GPS. Think about it... WWVB? WWV? Vertical
> pointing sun sensor?
>
>
>
>
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-- 

Chris Albertson
Redondo Beach, California