[time-nuts] Trimble Nortel GPSTM Boards
Bob Camp
lists at rtty.us
Thu Aug 1 10:31:17 UTC 2013
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.
More information about the Time-nuts_lists.febo.com
mailing list