[ntp:questions] how do you like the Trimble Resolution T

unruh 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.
>
> http://www.ebay.com/itm/260769578277?ru=http%3A%2F%2Fwww.ebay.com%3A80%2Fsch%2Fi.html%3F_from%3DR40%26_trksid%3Dp5197.m570.l1313%26_nkw%3D260769578277%26_sacat%3DSee-All-Categories%26_fvi%3D1&_rdc=1
>
> 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. 
>
> Sincerely,
>
> Ron
>
>
> 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
>>> <http://www.ioffer.com/info/redirect_notice?url=http%3A//item.taobao.com/auction/item_detail.jhtml%3Fitem_id%3D9a519ec253fb6de5012d1e206938da00%26x_id%3D0db1%23>,
>>>
>>> 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
>> about.
>>
>> 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.
>>
>> Terje
>



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