[time-nuts] UPDATE: DATUM 9390-52054 Grief again...

Luciano Paramithiotti timeok.it at gmail.com
Sun Apr 14 13:23:50 UTC 2013


I have a 9390-53120. The 16.368 reference for the GPS is coming from a
4 pin (14 pin size ) oscillator on the GPS interface board.
The other internal oscillator board mount a 1 MHz TCXO I never had
seen locked to GPS.
Normally I use it only for UTC time display.
This GPS use an antenna with 50dB gain, so I have added a preamplifier
to normalize its sensitivity.
I had two fault in 10 year of life on the power supply board.

Luciano
www.timeok.it


 2013/4/14 David I. Emery <die at dieconsulting.com>
>
> On Fri, Apr 12, 2013 at 11:48:47AM -0700, Burt I. Weiner wrote:
> > Sorry for the delay in posting this update.  Things have been hectic,
> > and then there was NAB.
> >
> > Here's what I've discovered:  The receiver started working after
> > about 6 hours of just sitting.  However, the 9390's internal Vectron
> > oscillator was quite a ways off frequency and did not want to lock
> > after trying to stabilize all night.  I had to tweak the adjustment
> > screw quite a ways and then, after a while, it locked.  Prior to this
> > episode the oscillator had been sitting at only a few E-12.  I
> > suspect that this oscillator has had an intermittent problem for a
> > long time, and I should not have had to tweak it as far as it wanted
> > to go.  The receiver portion has not failed in the few weeks since it
> > decided to start seeing satellites again.  Maybe because I had
> > tweaked the oscillator?
>
>         I have an ancient 9390 that has an ancient Trimble GPS board in
> it that takes a 16.368 reference synthesized from the 10 MHz standard in
> a PLL loop with a VXCO. This is used in the L band downconversion...
> and for timing generally and given that is PLL derived from the 10 MHz
> quite likely if the 10 MHz is significantly wrong the receiver won't
> find satellites.   I remember I had to fix this PLL in my box before the
> receiver in that box would lock up... initially the PLL wasn't locked,
> but the 16.368 VCXO output WAS present  - so for that receiver it has to
> be pretty close to right on to work.
>
>
> --
>   Dave Emery N1PRE/AE, die at dieconsulting.com  DIE Consulting, Weston, Mass 02493
> "An empty zombie mind with a forlorn barely readable weatherbeaten
> 'For Rent' sign still vainly flapping outside on the weed encrusted pole - in
> celebration of what could have been, but wasn't and is not to be now either."
>
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