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

Ron Frazier (NTP) timekeepingntplist at c3energy.com
Wed Feb 29 14:16:23 UTC 2012


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.

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

-- 

(PS - If you email me and don't get a quick response, don't be concerned.
I get about 300 emails per day from alternate energy mailing lists and
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Ron Frazier
timekeepingdude AT c3energy.com


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