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 <kb...@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 <paulsw...@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 <paulsw...@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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