Interesting. I wonder what other GPSDO units are out there in the cell
systems
which might find their way to the surplus market?
By the way, how do you get Lady Heather to show the plot of signal strength
vs
az/el? I tried all sorts of different graphing options and read through
everything I could find with no luck.
Peter
On 5/3/2012 8:02 AM, Mark Sims wrote:
Recently Sam managed to poke and prod a Trimble/Nortel GPSTM (NTGS50AA)
enough to wake it up out of its slumber and be recognized by Lady Heather.
The NTGS50AA is a version of the Thunderbolt done for Nortel. It has some
interesting features (like hot-upgradable firmware, single 24 or 48V power
input, cheaper than a tbolt, etc. It also has a few warts... no TSIP
command documentation being the main one and a few commands are definitely
different than the Tbolt.
The wakeup technique is rather crude and can take a couple of minutes
(shout a particular command into its ear until it wakes up). Trimble's
software manages to get it talking immediately. Duplicating the commands
that Trimble sends does not seem to work. Once it wakes up, it stays awake
until you power cycle it or run Trimble's software.
I purchased one of these units from an Ebay seller in Old Cathay (around
$70 or make offer plus $30 shipping) to see what it would take to add
support to Lady Heather. My unit came in a week or so later. I hacked a
48V power connection (literally) onto the board and powered it up with a
wall wart. After some futzing and puzzling over the proper ribbon cable
orientation between the main board and front panel board, I got the unit
woken up using Sam's technique and puzzled out the commands to make the
oscillator disciplining (time constant, damping, dac gain, etc) work. The
old survey location was in a sketchy Guatemalan smuggler's haven border town
at what looks like a private residence.
After running it a while, it became apparent that it works better than
the Thunderbolt. The temperature sensor does not have those glitches that
plague the tbolt. The receiver has a bit more sensitivity. And, best of
all, the oscillator is pretty much immune to external temperature changes
(the Tbolt oscillator makes a good thermometer). The reported OSC and PPS
rms errors are exceedingly low... you have to actively thermally stabilize
the Tbolt to approach these numbers. Hopefully this quality extends to its
phase noise, etc spec. It would be interesting to see what thermally
stabilizing the unit would do...
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