[time-nuts] What cut do I have?

Bob Camp lists at rtty.us
Mon Jan 28 17:56:29 EST 2013


Hi

The problem is that you wind up with a list that looks like:

AT 20 to 100 ppm
FC -20 to 60 ppm
IT -10 to 40 ppm
BT -40 to -60 ppm
SC ….

If you know the oven temperature, things can get narrowed down quite a bit. Don't take any of those numbers as exact. 

Bob

On Jan 28, 2013, at 5:06 PM, Magnus Danielson <magnus at rubidium.dyndns.org> wrote:

> 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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