[time-nuts] Trimble/Nortel 45000 GPSDO

bg at lysator.liu.se bg at lysator.liu.se
Sun Jun 10 22:06:07 UTC 2012


Hi Mark,

> I got in a couple of those Nortel GPSDO modules (marked 45000-00-B8
> GPSTM).   These are the single board version of the NTGS50AA modules that
> have a separate small front panel board.    They are hardware and software
> compatible (mostly).   Some immediate differences popped up.  The 45000
> board is at least 6dB LESS sensitive than the NTGS50AA (maybe 4dB less
> than a Thunderbolt).  This might not be a good receiver if you have signal
> level problems.

My Nortel GPSTM units are also less sensitive that normal Tbolts. Have not
quantified it in a controlled way. Are your GPSTMs also late revisions?
Newer than the NTGS50AAs?  If so that is strange, since performance
(sentitivity at least) is worse. Hmmm... it is not quite clear that the
full length PCB is more expensive to build than the separate cards, with
cable (including 4 20cm SMB coaxes)

I think it would be interesting to compare the different versions, to find
out why there is such a big impact on sensitivity.


> Mine came in with the 34310-T oscillator.   The NTGS50AA came with the -T2
> oscillator (but may be shipped with the -T).   Like the -T2,  the -T seems
> to not be temperature sensitive.   Although it is way too early to tell,
> the -T started aging in at a 1E-8 parts/day.   The -T2 started at around
> 1E-9 parts/day and settled down after three weeks in the 5E-12 parts/day
> range.

Mine have oscillators marked "STP 2254, Spec 34310 C1", and "49422-CR". I
have yet to arrange with a stable laptop to run LH on continously.

--

    Björn




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