[time-nuts] Fundamental limits on performance

Lux, Jim (337C) james.p.lux at jpl.nasa.gov
Thu Sep 17 16:01:58 UTC 2009


________________________________________
From: time-nuts-bounces at febo.com [time-nuts-bounces at febo.com] On Behalf Of Bruce Griffiths [bruce.griffiths at xtra.co.nz]
Sent: Wednesday, September 16, 2009 21:06
To: chris at chriscaudle.org; Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Fundamental limits on performance

Chris Caudle wrote:
> I found it interesting that one of the limits of stability seems to be the
> ability to process the crystals at high temperatures to drive off
> impurities.  The JHU crystals are apparently in some type of glass
> enclosure which can take the high temperatures, and the paper seemed to
> indicate that the standard metal capped packages can't take the higher
> temperatures.
>
>
Bliley BFG61 package:
http://www.bliley.com/index_088.htm
>
> Just seemed interesting, I would assume that the JHU guys know about those
> types of advances in packaging, but the paper didn't mention it.

I think it's safe to assume that the APL guys know a "lot" about this kind of packaging..<grin>


>
>
Look at the JHU site there is a little on the oscillator.
The BFG61 package uses an intermediate internal ceramic plate that more
closely matches the thermal expansion of the quartz crystal.

--  Similar to a fairly conventional "graded seal", I would imagine

There is a huge amount of "art" in building this sort of package (actually, there's a lot of art in building high performance oscillators in general).. I would imagine that there are a very limited number of people who actually are skilled at making the package, sealing it, etc.  It's not like it's a skill set or market that would justify training thousands of operators.

Same kind of thing as any limited production item (like high performance electron gun cathodes, etc.)



More information about the Time-nuts_lists.febo.com mailing list