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

[paul swed]

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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