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

[Tom Van Baak]

See pages 20-29 in the Mar-1981 HPJ for the "new SC-cut" 10811 article(s):

https://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1981-03.pdf

It talks about 10544A/C/B and 10811A/B in detail. It compares AT/BT/SC cuts.

Read especially "The SC Cut, a Brief Summary" on page 22.

/tvb


On 2/17/2021 6:38 AM, paul swed wrote:
> Bob
> I thought SC's were around a long time. (Not that I doubt you on that) This
> thing should be the 1970s vintage from the one bit I have found on it.
> Magnus always appreciate your comments. As I heat it up from room
> temperature what exactly would I look for? Sort of the
> temperature/frequency behaviors I see in various charts?
> When cold the units sit 4Hz high. and when warm its currently .119 Hz high.
> It used to go below by .6 Hz. Not sure what has changed.
> Regards
> Paul.
>
> On Wed, Feb 17, 2021 at 9:31 AM Bob kb8tq <kb8tq at n1k.org> wrote:
>
>> Hi
>>
>> If it was made before 1981 it pretty much certainly is *not* an SC. That’s
>> not to say it is an AT. A lot of crystal cuts got used in OCXO’s over the
>> years.
>>
>> My guess, it broke, somebody took it apart and threw away the defective
>> crystal. It was replaced with a random unit from the junk box and the ovens
>> were (effectively) turned off.
>>
>> Bob
>>
>>> On Feb 16, 2021, at 8:18 PM, paul swed <paulswedb at gmail.com> wrote:
>>>
>>> After a bit of research I am wondering if this odd unit was actually an
>>> attempt at a AT cut crystal reference. The temperatures seem to line up.
>>> Its certainly an alpha or less product.
>>> It was stable at 43 F.
>>> Was thinking about disconnecting the oven and bringing the leads out to
>>> manually control the temp. With a quality external temp meter. Then see
>> as
>>> the temperature is adjusted, does it follow an AT cut curve.
>>> As someone on the thread said "it maybe working as intended".
>>> Regards
>>> Paul
>>> WB8TSL
>>>
>>> On Tue, Feb 16, 2021 at 6:17 PM paul swed <paulswedb at gmail.com> wrote:
>>>
>>>> Hello to the group still working and decoding the AN/URQ-13 reference
>>>> oscillator. Bob had mentioned that the crystal should be at 85 C and
>> thats
>>>> right for a SC cut crystal. Would there be any reason that this
>> oscillator
>>>> is perhaps a AT cut crystal thats in the 30 C range. Just odd that the
>>>> front meter reads in the normal temperature range and the real
>>>> measurement is 40C. Makes no sense but they build AT cut crystals for
>> some
>>>> reason.
>>>> Ehat about the smaller ovens like Piezo's. Pretty sure I can find many
>>>> details on the Morion oscillators like the MV200.
>>>>
>>>> Other bits of details.
>>>> There are 2 discreet regulators that simply produce most likely a low
>>>> noise +/-8.5V. The Oven heaters seem to run on +15V and the divider
>> analog
>>>> circuits need 13V min to work. But not 15V. That seems to cause some
>>>> distortion.
>>>> The other circuit on the board attached to the oscillator is a buffer
>> amp.
>>>> It does have several meter resistors on it also.
>>>>
>>>> Regards
>>>> Paul
>>>>
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