[time-nuts] 10811 warmup

Rick Karlquist richard at karlquist.com
Sat Jan 20 17:51:28 UTC 2007


On this unit, I suspect the oven was not at the correct operating
temperature.  Thus, although it warmed up to some extent, it may
not have reached 80 degrees C.  The real diagnostic would be to
slide it out of the case and look at the voltages on the thermistor
circuitry.  However a crude check can be made by measuring the
oven current and comparing it to a good 10811.  If it is substantially
lower, that would be a red flag.  The fact that the frequency seems
to be fairly stable is no guarantee that you couldn't have the
wrong oven temperature.  I have never heard of a 10811 with a properly
working oven that was that far off frequency.  You need to realize
that crystals had to pass a frequency test before the lid was installed
on the crystal package.  This was all done under automation.  Thus it is
"impossible" for a crystal 100 Hz low to ever exist.  And AFAIK, we
never made one on purpose.

Rick Karlquist N6RK



Mark Amos wrote:
> Didier,
>
> My experience with 4 10811's with widely separated serial numbers is
> consistent with your
> numbers below. Between 6 and 8 minutes of warm up from ambient (18C) and
> they're stable at the
> target frequency as measured with a recently calibrated 5328A (one without
> a 10811 - since
> remediated!)
>
> The recent bad unit I bought on ebay behaved similarly - it warmed up and
> within 10 minutes it
> had stabilized around 9,999,915.
>
> It is adjustable between about 9,999,900 and 9,999,920 or so using the
> adjustment capacitor
> through the hole in the case.  EFC seems to function correctly as well
> with a little over 1Hz
> of adjustability with +-5 V.
>
> As has been suggested, it must be some kind of test unit (or perhaps one
> that failed QA?)
>
> I replaced it with one from AST Global - they had a great return policy,
> shipped fast and
> packed well.
>
> In any case, I've retired the bad one as a marker generator at 9.9999 MHz.
>
> Mark
>
> Message: 1
> Date: Fri, 19 Jan 2007 22:53:28 -0600
> From: Didier Juges <didier at cox.net>
> Subject: Re: [time-nuts] Bad batch of HP10811's
> To: Discussion of precise time and frequency measurement
> 	<time-nuts at febo.com>
> Message-ID: <45B1A048.9090207 at cox.net>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Warmup data on the HP 10811:
>
> Here is some data collected on the internal HP 10811 timebase in my HP
> 5370A counter, which had been turned off and plugged off for about 3 days.
>
> 21:39:25,  9999798.6
> 21:39:35,  9999806.0
> 21:39:46,  9999822.6
> 21:39:55,  9999836.8
> 21:40:06,  9999853.2
> 21:40:15,  9999866.8
> 21:40:26,  9999881.7
> 21:40:35,  9999892.4
> 21:40:46,  9999904.1
> 21:40:56,  9999913.1
> 21:40:58,  9999915.2
> 21:41:07,  9999923.0
> 21:41:16,  9999930.1
> 21:41:25,  9999936.5
> 21:41:36,  9999944.0
> 21:41:46,  9999949.3
> 21:41:55,  9999954.3
> 21:42:06,  9999959.9
> 21:42:15,  9999964.0
> 21:42:26,  9999968.6
> 21:42:35,  9999971.8
> 21:42:45,  9999975.2
> 21:42:54,  9999977.9
> 21:43:05,  9999981.0
> 21:43:17,  9999983.9
> 21:43:26,  9999985.9
> 21:43:35,  9999987.8
> 21:43:46,  9999990.0
> 21:43:55,  9999991.3
> 21:44:07,  9999992.9
> 21:44:16,  9999994.0
> 21:44:25,  9999994.9
> 21:44:36,  9999996.1
> 21:44:45,  9999996.9
> 21:44:56,  9999997.7
> 21:45:06,  9999998.3
> 21:45:15,  9999998.9
> 21:45:17,  9999999.0
> 21:45:19,  9999999.1
> 21:45:21,  9999999.2
> 21:45:24,  9999999.3
> 21:45:26,  9999999.4
> 21:45:36,  9999999.7
> 21:45:45,  9999999.8
> 21:45:56,  9999999.9
> 21:46:05,  9999999.9
> 21:46:08,  9999999.9
> 21:46:10,  10000000.0
>
> After that, the display was a stable 10,000,000.0 for the next 15
> minutes (one reading was 10,000,000.1), then I stopped the data
> collection.
>
> The counter used was the HP 5334B with the Thunderbolt as external
> reference.
>
> Ambient temperature: about 22 degrees C (cool)
>
> Bottom line: about 200 Hz from a cold start and about 7 minutes to
> within 0.1 Hz of final frequency.
>
> Didier KO4BB
>
>
>
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