[time-nuts] Nortel/Thunderbolt questions

Chris Albertson albertson.chris at gmail.com
Fri Jul 12 19:02:09 EDT 2013

The altidutes don't match because each is relative to something different.
 The GPS is likely referenced to the WGS84 spheroid and the one on the USGS
top map is mean sea level.  Check up what is is relative to there can be a
lot of difference.

On Fri, Jul 12, 2013 at 12:56 PM, Jim Sanford <wb4gcs at wb4gcs.org> wrote:

> All:
> My Nortel receiver has been running for 6 days now.  I am running the Lady
> Heather software, but also have TBOLTMON.  It shows my position fairly
> well, but I have seen a negative altitude, and am currently seeing 1565'
> altitude.  Based on local maps and the GPS in the car, I believe the
> antenna to be no higher than 1280'.  I get lock with 4 to 6 satellites
> colored green.  I have seen PHASE LOCKED, but am currently seeing "recovery
> mode" and the LOCKED LED on the unit is flashing, which I think I remember
> means recovery.
> I have several questions:
> 1.  Sometimes position is displayed in yellow, sometimes in white. What is
> the significance of the color?
> 2.  I see TC 100.0 sec, DAMP1.200, GAIN 1.2 Hz/v, INIT 3.00V. When I go to
> KE5FX site, his values for TC, DAMP, Gain and INIT are very different.  In
> particular, if DAMP is damping in a control loop, I am not surprised that
> my very overdamped unit is not locking.   Question:  Are these parameters
> that will converge, or are they parameters I should try to set?  The
> heather.cpp files suggests that they may be settable, but does not say how.
> 3.  On my plot, I see an RMS value in green, which suggests to me that
> something is happy with the DAC voltage, even if very different from
> John's.  The scale is 100000uV/div which suggests to me that it is NOT
> locked.
> 4.  On my plot, I see an RMS value in yellow, which suggests to me that
> the temp is OK, but the scale on temp is growing.... at the momoent,
> 10mC/div; John's is 50 mC/div, but a much smoother plot than mine.  What is
> this telling me?
> POSITION status are all OK, even though altitude is bad.
> Can anyone help me understand what I am seeing, and in particular, why it
> won't lock, or stay locked, when it is seeing good sat signals?
> Thanks!
> Jim
> wb4gcs at amsat.org
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Chris Albertson
Redondo Beach, California

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