Mon Jan 3 15:02:28 UTC 2011
goal. There were several customers beyond Nortel in the running early on.
The whole idea of un-heated (outdoor box) "nano cells" was around a long
time before it became real. Weather the low end was a Nortel need that they
later dropped or from one of the other guys - no clue. Far to many beers
between now and when I heard the story to remember that sort of detail.
I've never seen any frequency vs temperature data on the "double oven"
10811's that shows they are significantly better than a normal part. HP
apparently never published any data. They also never used the approach
again, despite it's being pretty cheap to build (added parts cost). Looking
at the design, it likely isn't a very low gradient device...
Watching a Z380x do it's prediction stuff, aging seems to be the big issue.
Some of my boxes have taken weeks to get to an acceptable (few us) number.
If there's a weakness to the startup under normal conditions, aging /
retrace is the issue.
The heater jacket design is indeed a bit of overkill for the need, but
that's not the first (or last) time HP has done that in a piece of gear.
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Mike S
Sent: Monday, January 10, 2011 8:40 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] 10811 foam enclosure
At 07:59 AM 1/10/2011, Bob Camp wrote...
>The spec they were after was a warmup to "on frequency +/- 1x10^-8"
>from -40 C sort of thing. I believe the warmup time was under 15
>minutes, but I don't know the exact number.
Nope. It was only spec'd for operation from 0-50C. It was required to
achieve satellite lock within 60 minutes of powerup, but only had to
achieve +/- 1 us (PPS) while locked. Freq spec was < 10E-9 one day
average. You don't even need an OCXO to do all of that.
As I already stated, the warmup/training spec allowed 24 hours, after
which it was expected to be able to holdover for 24 hours within 7 us.
This, while experiencing temperature cycles (0-30C, 20-50C). The
successor, the GPSTM, doubled the warmup to 48 hours, but added an
additional temperature range (35-65C) to the holdover requirement.
The double oven was there for holdover stability, not warmup time.
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