Bob:
Well, this is discouraging. The receiver seems to work -- receives the
sats it should. Seriously doubt there's any multipath out here in the
boondocks. Maybe some tree absorption at very low elevation, but very
little in the way of reflectors. I'm on 10 acres on a hillside, with
trees in the distance.
Jim
On 8/2/2013 9:24 AM, Bob Camp wrote:
Hi
Either a blown receiver (likely the SAW filter) or antenna multi path.
Bob
On Aug 1, 2013, at 8:45 PM, Jim Sanford <wb4...@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.
jimwb4...@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, gandal...@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_steinm...@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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