[time-nuts] Trimble Nortel GPSTM Boards

[GandalfG8 at aol.com]

Hi Bjorn,
 
Many thanks for the tip, I'd seen discussions on the two part boards,  
NTGS50AA, but hadn't realised the extent to which this version had also been  
mentioned.
Given that it was discussed as recently as early July, including  comments 
on the wheel I've just reinvented, and that I did read those  comments at 
the time, I think it's perhaps time I took a break, or wrote out 500  
times..."I must pay more attention" :-)
 
Regards
 
Nigel
GM8PZR
 
 
 
In a message dated 01/08/2013 20:21:00 GMT Daylight Time, bg at lysator.liu.se 
 writes:

Hi  Nigel!

This has been discussed before in time-nuts. I have two of the  big boards, 
but they are not running right now. If I remember correctly the  big ones 
are more of a cost reduction model compared to the 2 board split  solition. 
Giving lower SV snr than the split version. 

But my ran  just fine compared to my standard Tbolts.

--
Björn


Skickat från min Mobil 

--------  Originalmeddelande --------
Från: GandalfG8 at aol.com 
Datum:  2013-08-01  11:09  (GMT+01:00) 
Till: time-nuts at febo.com  
Rubrik: Re: [time-nuts] Trimble Nortel GPSTM Boards 

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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