[ntp:questions] SNTP server + ntpd 4.2.4 client
unruh-spam at physics.ubc.ca
Wed Mar 19 17:16:03 UTC 2008
"Richard B. Gilbert" <rgilbert88 at comcast.net> writes:
>Steve Kostecke wrote:
>> On 2008-03-19, Noob <root at localhost> wrote:
>>>Does the GPS18LVC provide an oscillator to serve time even when there
>>>are not enough satellites in sight?
>> No. You'll have to pay (much) more than $70-$80 if you want a good
>> hold-over oscillator.
>With something like 27 NAVSTAR (GPS) satellites aloft, there should
>almost always be seven or eight above the horizon. Satellites more than
>ten degrees above the horizon are preferred!
>I've never used the GPS18LVC (I have a Motorola M12+T) but if you know
>your exact location you only need one satellite to get the time. There
>are four equations in four unknowns (lattitude, longitude, elevation,
>and time). Not knowing any of these variables, you need four
>satellites. Once you know your location a single satellite is
>sufficient to solve for time.
Yes, but the internals of the receiver are not available to the user. Thus
the 18LVC uses a minimum of 4 since it is quite possible that it is
moving-- it is designed for OEM truck operations. Thus the 18LVC claim, if
I recall correctly, that it needs 4 If less than 4 for a few 10s of seconds
it stops delivering a PPS. On the other hand, as you say, if you have any
view of the sky at all, that should not be a problem.
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