[time-nuts] Something better than a Thunderbolt?
nerd at verizon.net
Thu May 3 14:43:01 UTC 2012
On 5/3/2012 10:32 AM, Sam wrote:
> You can display signal strength vs az/el by pressing the letters "s a s" on your keyboard.
> S = Survey
> A = Antenna
> S = Signals
> ----- Original Message -----
> From: Peter Gottlieb
> [mailto:nerd at verizon.net]
> To: Discussion of precise time and frequency
> measurement [mailto:time-nuts at febo.com]
> Sent: Fri, 04 May 2012 00:00:22
> Subject: Re: [time-nuts] Something better than a Thunderbolt?
>> Interesting. I wonder what other GPSDO units are out there in the cell
>> 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
>> az/el? I tried all sorts of different graphing options and read through
>> everything I could find with no luck.
>> 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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