[time-nuts] Trimble Nortel GPSTM Boards

Bob Camp lists at rtty.us
Fri Aug 2 09:24:45 EDT 2013


Hi

Either a blown receiver (likely the SAW filter) or antenna multi path.

Bob


On Aug 1, 2013, at 8:45 PM, Jim Sanford <wb4gcs at wb4gcs.org> wrote:

> 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
>>> 
>>> 
>>> 
>>> 
>>> _______________________________________________
>>> time-nuts  mailing list -- time-nuts at febo.com
>>> To unsubscribe, go to
>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the  instructions there.
>>> 
>>> _______________________________________________
>>> time-nuts mailing list -- time-nuts at febo.com
>>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>> 
> 
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.



More information about the time-nuts mailing list