[time-nuts] Trimble Nortel GPSTM Boards

[Jim Sanford]

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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