[time-nuts] UPDATE: DATUM 9390-52054 Grief again...
David I. Emery
die at dieconsulting.com
Sat Apr 13 22:45:04 UTC 2013
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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