[ntp:questions] how do you like the Trimble Resolution T
unruh at invalid.ca
Wed Feb 29 15:56:10 UTC 2012
On 2012-02-29, Ron Frazier (NTP) <timekeepingntplist at c3energy.com> wrote:
> Hi Terje,
> Thanks for the info. I really want to run my antenna indoors if
> possible, so this unit might not be for me. It's good to know about the
> sawtooth correction stuff though.
> I forgot to post the original link to the Ebay auction. It's item #
> 260769578277. The link below should work, but, if not, you can put the
> item number into the Ebay search box.
> Other than the Sure board which has been mentioned, are there any other
> modern, hi sensitivity, timing GPS's which cost less than $ 100. Many
> of the ones mentioned seem to be older technology like this Trimble.
Teh standard is the Gamin GPS 18x (make sure to get a newer unit or you
will have to upload a patch to it to fix the problem that it sometimes
sends teh nmea sentences too late). The Sure I am getting worried
about-- I thin kthe antenna they send with it is defective sometimes.
> On 2/29/2012 3:36 AM, Terje Mathisen wrote:
>> Ron Frazier (NTP) wrote:
>>> Hi all,
>>> Is anyone using the Trimble Resolution T GPS for timing? I was looking
>>> at an ad for one on ebay. For my purposes, any accuracy under 1 ms is
>>> great. I don't have to have 15 ns. Of course, smaller numbers are always
>>> better. Is this device hard to setup and program for PPS and use with
>>> NTPD? What accessories are needed?
>>> This is what the ad says is included:
>>> quote on ->
>>> The Resolution T Starter Kit provides everything you need to start
>>> integrating the module into your application. The kit includes an
>>> active, external 5-VDC Bullet-style antenna
>>> 50 feet of RG-59 cable, and an AC/DC power adapter. The starter kit
>>> enclosure includes a mother board that provides serial output, and a
>>> serial interface cable. A reference manual and monitor programs are
>>> provided on CD-ROM.
>> I could not get to that taobao link...
>>> <- quote off
>>> I notice the unit only tracks 12 satellites and has 141 dbm sensitivity,
>>> which seems to be less than some units. Is that a problem?
>> Should not be as long as you can get an outside antenna location.
>>> Finally, what is sawtooth correction?
>> Most GPS chipsets run off a 10 MHz clock, which means that the best
>> they can do is to locate the actual PPS edge on the nearest 100 ns
>> boundary, i.e. you'll get an error of +/- 50 ns which the gps knows
>> Timing gpss like the Oncore UT+ sends the known PPS offset as part of
>> the serial timestream, telling NTPD (or any other recipient) how
>> early/late the pulse actually did arrive.
>> This is nice to have if you also have a stabilized clock source for
>> your motherboard, along with hw to detect and measure the interrupt
>> latency, i.e. the time between the PPS pulse and when the OS driver
>> wakes up and notices it.
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