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

[paul swed]

Bob
Oh this unit is a alpha or maybe not even that. So it would have been NRL
direction to FE from what very little I can find. I honestly looked at the
curves and did not see AT as a U shape. Hmmmmm. Thats a concern. Will look
far far more carefully. The charts I looked at had many xtal types SC BT AT
2-3 others and most looked like a low frequency then flat then high
frequency. Was going to say a S but thats the wrong shape.
Regards
Paul

On Thu, Feb 18, 2021 at 9:54 AM Bob kb8tq <kb8tq at n1k.org> wrote:

> 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>
> 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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>
>