Here is a plot from the latest GPIB hack which reads frequency and phase
about once per second. Only the phase is shown here. Small tweeks to the
fine freq standard adjustment take several minutes to take effect. Is
the fine adjustment tweeking some parameter related to the oven??? On
12/11/2011 07:34 AM, Larry McDavid wrote: > Chuck, what is the time
scale in your plot? That is, why does "1400" = > 430 seconds? > > Larry

The 1992's A input goes to the Thunderbolt. >> The 1992's B input goes
to its time base output. >> The counter is set to "A rel B" >> >> Here's
a blow-up of the phase plot. In this case it takes some 430 >> seconds
for the >> phase offset to cycle 360 degrees. In other words, there is
1/430 Hz >> frequency difference. > ... > -- Chuck Forsberg WA7KGX
N2469R caf@omen.com www.omen.com Developer of Industrial ZMODEM(Tm) for
Embedded Applications Omen Technology Inc "The High Reliability
Software" 10255 NW Old Cornelius Pass Portland OR 97231 503-614-0430

Chuck wrote:

I doubt it, but I do not have actual knowledge of the inner
workings.  I have found that the heat loss (I assume) through the
open adjustment plug screw causes an error -- you can get them
adjusted as closely as you can (in my experience, about 1E-9 with
lots of hair-pulling) and they will sit there stably for as long as
you want, then when you put the plug screw back in they drift several
parts in e-9 or more over a period of 10-15 minutes and stabilize at
a new value.

The good news is that the Racal oscillators in my 1992s are very
stable long-term performers -- and significantly less
position-sensitive than many others.  So, you don't have to adjust
them very often.  The bad news is that getting them really, really
close to the desired frequency is like herding cats.  Other than the
flaky pushbuttons on some of them, I have found that 1992s are
extremely dependable.  When a 9-digit counter will do, they are a
great choice.  (Of course, as time/frequency nuts we quickly outgrow
9-digit counters.  Doesn't every measurement require 12 digits
referenced to an H-maser?)

I think it's been asked, and recently, but I haven't seen a positive
response.  Does anybody have schematics for the Racal OCXOs they can
make available?

Best regards,

Charles

On 12/13/2011 2:44 PM, Charles P. Steinmetz wrote:

Charles, I have a hand drawn circuit diagram of the 9442 rapid warm up
oven which I made, no guarantee as to accuracy, a copy of which you are
welcome to.

There is a person advertising others on the net, but he never has
bothered to answer my  repeated emails, see:
http://www.antronic-data-systems.co.uk/page76.html

In any case he charges more than I have paid for the ovens themselves on
eBay.

The one in the US mil version of the 1992 was only used in that from my
experience.  Yes, it is a good oven, and tricky to adjust.  If you want
better accuracy, that's why there is an external input :^)

Dan