[time-nuts] HP10544A Confusion

[Jim Flanagan]

Jimmy -
I found out the answer the question that I was asking you in
my previous email.

A fellow who is well versed in the HP oscillators (10544 and
10811) let me know that the 10544 oscillators used BOTH the
AT crystals and the BT cut crystals.  This is why I was
seeing what I was seeing.  Therefore I do need to tweak
the temperature for a freq MAX.

You may want to amend your website to point out that the
HP10544A used BT cut crystals at some point.  All of the web
references that I ran across pointed to the AT crystal
as the only cut used during the lifespan of this oscillator.
Take care-
Jim
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Hi..
I need help understanding a few things in regards to my
10544A oscillator.
I was given an osc about 5 years ago that did not have the
oven controller.  The owner at that time had built his own
version which did not work well.  I completely removed
everything he had done and duplicated the original oven
using the osc schematics that are available.  At that point
the osc went on the shelf until a couple of weeks ago.  I
decided to go ahead and calibrate the oven temperature in
order to select the correct resistor to set the temp at the
turning point.
Here is my confusion:
I understand that the 10544 oscillators used AT cut
crystals, which means that after warmup, I need to tweak the
temp for a freq MIN.  Whereas, for an SC cut xtal osc we
would be looking for a freq MAX.  For both xtal cuts the
turning point is typically set for somewhere in the 75 - 85
C range.  I see where my 10544 osc is sitting about 1.5KHz
LOW at room temp and then increases in freq at warmup (OVEN
temp rising).  I thought that at room temp the freq (for AT
osc) would be HIGH and decrease in freq as the oven warms.
After a full warmup, I would then adjust the temp slowly,
watching the freq for a min, at which time, as the oven is
made hotter, the freq would then start in the opposite
direction(positive).
In my mind, my osc seems to act as though it is using an SC
cut crystal...
Is my thinking all wrong here?
I’ve been studying he classic df/f vs Temp curves and my osc
appears to be opposite of the curves, assuming my osc does
use an AT xtal.
I would appreciate someone setting me straight in regards to
this..
Thanks
Jim
jflan at tampabay.rr.com