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

unruh unruh at invalid.ca
Fri Mar 2 02:30:43 UTC 2012

On 2012-03-02, Ron Frazier (NTP) <timekeepingntplist at c3energy.com> wrote:
> On 2/29/2012 6:12 PM, Chris Albertson wrote:
>> On Wed, Feb 29, 2012 at 2:29 PM, Bruce Lilly<bruce.lilly at gmail.com>  wrote:
>>> On Wed, 29 Feb 2012 14:16:23 +0000, Ron Frazier (NTP) wrote:
>>>> 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.
>> Don't worry.  Even the UT+ which is well over ten years old is
>> fantastically good compared to what NTP needs.   It  has better specs
>> then many newer units and for timing, I'd say better specs then MOST
>> new units.    $100 is a good budget.  You can buy a $25 antenna and a
>> $20 GPS receiver and some cables and a power supply.     I can safely
>> say that anything with the "trimble" name on it, if it was designed
>> for timing is almost "overkill" for use with NTP.
>> As long as it is a timing (not a nav) GPS and you plu the PPS into a
>> real serial port (not USB) you will be good to go with accuracy as
>> good as NTP can handle.    But those are importent: (1) timing not nav
>> and (2) real rs232 serial.    Once you have those two the rest is just
>> personal preferences and what you were about to find on eBay that day.
>> Now if you needs included precision timing (something NTP can't do)
>> and you cared about nano and pico seconds and frequency standards at
>> the 1E-13 level then yes things that NTP can't notice become
>> important.
>> The lowest cost, good units are the UT+ and then search eBay for 26dB
>> antenna.  And yo'll find a bullet shape white one.   These will fit on
>> a standard American 3/4" iron pipe flange with 4 bolts.   That would
>> be the lowest cost profesional level setup and will run with the PPS
>> at about 50nS (1 sigma)  But there are many other good setups.
>> Don't worry about if they are "new" tech.   It's like worrying if a
>> 1968 Chevy Corvett is fast enough to get  you to work in the morning.
>> Chris Albertson
>> Redondo Beach, California
> Chris,
> Thanks for all the info.  You've just about convinced me that, if I buy 
> another unit other than my USB BU-353, it should be a Motorola Oncore 
> UT+ or the Trimble Resolution T, or another Trimble, depending on 
> availability.  So, that brings up even more questions.  I have each of 
> the following questions for each of these units:

IF all you need is to get the time to one or two micro seconds, any gps
receiver with a PPS output is good. In order to make use of anything
better, you will have to buy a special card for your computer with an
onboard crystal and hardware comparison of he PPS with that. PPS
interrupts are only good to a few usec.

What he calls a timeing receiver is one which a) can do a site survey
and remember the location where it is at. and b) reports ( in a
proprietary format) the sawtooth corrections, so that you can get the
PPS to about 10ns. If that is not what you need, then any gps with a PPS
is fine. 

> A) You said it has to be a timing GPS.  How do you tell?  I haven't seen 
> that term in any of the data sheets.
> B) How would I program the unit?  I prefer to change the baud rate to at 
> least 57,600 and set the NMEA sentence for GPZDA only or GPGGA only.

Most timing gps have proprietary commands. Units liek the Sure or the
Garmin 18 use nmea sentences. 

You do not need 57600.

> C) Is documentation readily available for the unit?
> D) Would it need a firmware update and is that even possible for these 
> older units?
> E) What accessories would I need to get it going and are they 
> available?  Antenna?  Specialty cables?  Power supply?  Connectors?
> F) I really don't prefer to put the unit or antenna outdoors for two 
> reasons.  There is the issue of plugging the hole in the wall or 
> window.  Also, masts and wires can be a lightning hazard, particularly 
> in GA.  We have the 2nd highest incidence of lightning in the US.  Ham 
> radio equipment incurs similar risks.

If you are not going to put it outside then get a unit with high
sensititivity, (eg the Sure). 

> So, would these units, with the recommended antenna, be capable of 
> working indoors?
> Any other random data I need to know about working with older equipment?
> Sincerely,
> Ron

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