[time-nuts] Trimble Nortel GPSTM Boards

Mark C. Stephens marks at non-stop.com.au
Thu Aug 1 21:02:24 EDT 2013


Buggy firmware? Anyone seen the firmware floating around?

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of Jim Sanford
Sent: Friday, 2 August 2013 10:46 AM
To: time-nuts at febo.com
Subject: Re: [time-nuts] Trimble Nortel GPSTM Boards

I am seeing the same thing -- big jumps every single time a satellite is counted or not.  Elevation mask 10 degrees, which should be very good and stable for my location.  The unit also insists on converging to a bat altitude, then after a while declares stored position bad . ..  then declares position good, even with bad altitude.

Ideas appreciated.

Jimwb4gcs at amsat.org

On 8/1/2013 6:31 AM, Bob Camp wrote:
> Hi
>
> You may have your elevation mask set to low for your antenna or a multi path issue from some other source.  If the survey location is good to under a meter and the signals are good, there should be very little shift as sats are picked up or dropped.
>
> Bob
>
> On Aug 1, 2013, at 5:09 AM, GandalfG8 at aol.com wrote:
>
>> Hi Charles
>>
>> Thanks for your comments, the surveyed position on this is looking 
>> pretty good but what I have now realised is that the severity of the 
>> jumps  seems very much related to the number of sattelites being tracked.
>>
>> Switching from 8 to 7, or 7 to 8, sats seems to produce the biggest  
>> step change whilst switching in either direction between 5 and 6, for  
>> example, doesn't seem to show up at all on the monitored DAC voltage.
>> Ok, I take that back, it does still seem to depend on the number of 
>> sats being switched between but I've just seen a switch from 5 to 4 
>> sats induce a very noticeable step change in DAC voltage, so the 
>> relationship  doesn't appear to be linear.
>>
>> Unfortunately I need to power this down now for a few days but  will 
>> investigate more later.
>>
>> Regards
>>
>> Nigel
>> GM8PZR
>>
>>
>> In a message dated 01/08/2013 09:45:24 GMT Daylight Time, 
>> charles_steinmetz at lavabit.com writes:
>>
>> Nigel  wrote:
>>
>>> at times I'm seeing very noticeable step changes in the DAC  voltage 
>>> on this one as that happens.
>>>       *   *   *
>>> I am a bit surprised by the extent, a  Mark Sims online plot from
>>> 2012 shows some correlation on an NTGS50AA  but not as noticeable as 
>>> this, and I  don't recall seeing  anything quite so pronounced on a
>> Thunderbolt.
>>
>> IME (with TBolts), the  magnitude of the DAC steps with constellation 
>> changes varies with the  accuracy of the positional data used by the 
>> GPS.  To a point, the  more accurate the survey, the smaller the DAC 
>> jumps will be.  (Other  errors prevent reducing the 
>> constellation-change DAC steps to  zero.)
>>
>> Mark has commented here on survey accuracy, and the methods he  used 
>> in Lady Heather to maximize it.
>>
>> Best  regards,
>>
>> Charles
>>
>>
>>
>>
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