[time-nuts] What cut do I have?

[Magnus Danielson]

Hi Bob and Bernd,

I don't know *why* I had you in mind for this question? :)

On 01/28/2013 10:54 PM, Bernd Neubig wrote:
> Hi Bob,
>
> you are right. Sorry for my mistake.
> FC (and some) IT cut crystals are used in OCXO, because the curvature around
> the upper turn point is "flatter" than for an AT- cut with the same
> turn-over temperature.
> IT-cut crystals are sometimes used, when the oven temperature must be in the
> range 95 to 100°C, because the operating temp of the OCXO must cover the
> whole "industrial" temperature range up to 85°C.
> The yield is higher than using SC-cut crystals for such applications.

OK. It would be handy to have a list giving the 25°C frequency vs. the 
nominal for the AT, BT, SC, FC and IT cuts, just as a handy short-hand.

The previous postings where not very clear, so I had to ask the stupid 
question again.

Cheers,
Magnus

>
> Bernd
>
> -----Ursprüngliche Nachricht-----
> Von: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] Im
> Auftrag von Bob Camp
> Gesendet: Montag, 28. Januar 2013 18:40
> An: 'Discussion of precise time and frequency measurement'
> Betreff: Re: [time-nuts] What cut do I have?
>
> Hi
>
> The only time I've seen them used in OCXO's both the FC and IT were run on
> the upper turn (just like an AT). Thus the frequency goes down as it warms
> up.
>
> Bob
>
>
>
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Bernd Neubig
> Sent: Monday, January 28, 2013 11:48 AM
> To: 'Discussion of precise time and frequency measurement'
> Subject: Re: [time-nuts] What cut do I have?
>
> Hi,
> IT and FC cut crystals are not very often used in OCXO. But if, then the
> lower turn point is used (below the inflection temperature), which means
> that the cold oven starts at a lower frequency, which increases with warm-up
> - same direction as for SC-cut crystals.
>
> Regards
>
> Bernd
> DK1AG
>
> -----Ursprüngliche Nachricht-----
> Von: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] Im
> Auftrag von Bob Camp
> Gesendet: Montag, 28. Januar 2013 03:39
> An: Discussion of precise time and frequency measurement
> Betreff: Re: [time-nuts] What cut do I have?
>
> Hi
>
> It could also be an AT, IT or FC cut. A lot depends on just how hot the oven
> is running. Best bet is indeed AT.
>
> Bob
>
> On Jan 27, 2013, at 7:40 PM, Magnus Danielson<magnus at rubidium.dyndns.org>
> wrote:
>
>> On 01/28/2013 01:01 AM, Ed Breya wrote:
>>> If you meant to say the frequency starts out too high when the oven
>>> is cold, then I think it's AT cut.
>>
>> OK. I looked at the previous posts and it was not very clear from
>> them,
> and I was too lazy/busy to heat up an idel AT OCXO. I just felt the +41.4
> ppm deviation was a little low for an AT cut.
>>
>> Meanwhile, out of 22 LPROs tested, only 3 has BITE error, so 19 locks up.
> Out of 4 cesiums tested, 3 locks up and one fails. Trimming needed on all.
>>
>> Cheers,
>> Magnus
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