[time-nuts] AN/URQ13 reference AT cut crystal?

[Bob kb8tq]

Hi

> On Feb 18, 2021, at 9:39 AM, paul swed <paulswedb at gmail.com> wrote:
> 
> The conversation may have strayed a bit.
> 
> Do need to address one comment that the crystal is a junk box unit. Its sealed and is a FE crystal. Granted as is, it just may be junk. But it originally most likely wasn't.
> Well a good/bad test last night.
> 
> Manually controlled the oven temp and strange results. Looks like a SC xtal but flip the graph upside down.

The AT is a “graph upside down” SC.

> Also with a heater supply voltage of 15 Volts it can never get to 66 C or more. With 15 V it hovers at 40 C. Needed to go to 20 V. Heater is 140 ohms total.

So that is not an OCXO anymore. Either it’s very broke or somebody 
has done a lot of customization on it. Why / when / for what reason? 
No way to really know. 

> 
> At room temp the oscillator is 4 hz high then drops .6 hz below 5,000,000 Mhz at 66.5c.
> But then the frequency started going back up at 67c and just kept going. Even with the oven heat off it kept going up. After a hour and the temp dropped to 60C it was +4.5 Hz. 
> Sort of totally unexpected results.

Very normal results for an AT that was built as a crystal for an XO. 
( = uncompensated TCXO). +/- 1 ppm 0 to 50C is a pretty common spec.

> 
> I plan to restart the test tonight or tomorrow and slow the warm up down even further as I do believe the turn over point was hit. But the upside down U shaped curve made no sense. Also I do not recall seeing a crystal curve that looked like an upside down U.

You would need to get down to around -20 C to see the other side of the AT curve. 

Bob

> Regards
> Paul
> WB8TSL
> 
> On Thu, Feb 18, 2021 at 7:13 AM Poul-Henning Kamp <phk at phk.freebsd.dk <mailto:phk at phk.freebsd.dk>> wrote:
> --------
> Bob kb8tq writes:
> 
> > Turning an “idea” into a production capable part involves making many 
> > batches of test samples. Think in the thousands of batches and hundreds
> > of parts in each batch. You have a “search” process at the blank chopping
> > level. You also have a search at the resonator fabrication level. Getting the 
> > chopping part right is only a small part of the whole process….
> 
> I realize this used to be a manual process, but today I would expect
> that you could automate a lot, of not most of it, if you wanted to ?
> 
> It would still be a lot of work, and very expensive, but like
> biochemist trying out hundred of thousand compounds from their
> "libraries", robots really lower the cost.
> 
> The real question must therefore be, if anybody reasonably expects
> there to be any superior "new" cuts to find in the first place ?
> 
> What properties would you program a quartz-crystal-prototyping robot to search for ?
> 
> Which parameter(s) of current crystal-cuts are "their weak point" ?
> 
> -- 
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe    
> Never attribute to malice what can adequately be explained by incompetence.
> 
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