Warren,
there is a report somewhere of resetting the oven temp in a HP 10811
to exactly find the turnover temperature.
How high is this on your list of things to do to improve a HP 10811?
Does it make the double oven unnecessary?
cheers, Neville Michie
On 27/03/2010, at 10:49 AM, WarrenS wrote:
I was asked:
"what advantage is there to those of us, on stable ground and not
in rolling ships, of finding an orientation where any rotation
will move the frequency in one direction?"
My answer to a Good question:
When the Osc is orientated so that any tilt angle changes its freq
in the same direction,
then it is at the Zero-G turn over point and the slope of freq
difference vs. angle is at zero.
This causes small angle changes to have very little effect on the
freq.
Works about the same way as finding the turn over temperature of an
crystal.
that said,
It's mostly still just about NS "nuttery stuff".
The Zero-G effect only works great for very small angles,
like lifting an edge less than a 1/8 to a 1/4 inch.
The right orientation can make a difference, though.
The stuff that I'm working on is setting on my work bench where I'm
looking for things that cause small freq changes of 1e-12 or less.
If the Osc is not in the right orientation, then any movement of
it, will change its freq, more like a tilt meter than a stable Osc.
If you want to make a very sensitive tilt angle meter all one needs
do is set the Osc box on any of its sides.
Another thing I use it for is to test high resolution Freq meters.
Using a calibrated wedge that I can then slide under one edge of
the zero-G Osc box, I can
make small, variable, repeatable, freq changes of under 1e-12
resolution, something pretty hard to do otherwise.
If I want to make BIG changes like 1e-10, I can rotate the box on
any of its sides and still use the wedge,
and for a quick check of new equipment, I just turn the box over
which then gives a couple of parts in 1e-9 freq change.
It makes a weird but simple and indispensable variable freq source
that is useful for many things, such as checking the LOOP TC of a
TBolt.
ws
***********************
Peter asked:
"Could you post a drawing or photo showing the proper orientation
of the
zero-G axis?"
Simple answer ... NO see Bob's response on why.
BUT probable because they are made very similar, the double oven
units I've done it to, all end up at about the same angle.
Just imagine the worse possible angle to try and mount it (on one
of its corners) and that'll be close :-).
I hold them in place with a bunch of specially cut and shaped foam
stuffed all in a slightly bigger but tight fitting box.
It helps to have a fast reading High resolution freq difference
meter to find and do fine adjustment on their final angle.
I do each axes separately. The final results you want is when no
matter which way it is tipped, The freq always moves the same
direction.
The improvement for small angles is really amazing, up to 100
times better.
BTW there are two zero-G turn over points, one is at min freq and
one is at max freq, which are about 180 deg different from each.
This is good to remember in order to place it so that you can get
its cables out.
ws
*****************
Hi
The true zero axis will be different for each individual oscillator.
Bob
*************
Behalf Of Peter Putnam
Sent: Friday, March 26, 2010 12:08 PM
Warren,
Could you post a drawing or photo showing the proper orientation
of the
zero-G axis?
Thanks,
Peter
****************
WarrenS wrote
... snip .... snip ....
I know how to make major improvements to the 10811 so that the
standard stuff does not have ANY measurable effect on its freq.
Nothing really magic, mostly simple things like secondary PS
regulators, an outer oven heater wrap and controller, some internal
span and reference voltage adjustments, tilt it on its Zero G axes,
add an RF buffer, isolate or have a less sensitive EFC input, a fine
freq adjustment pot, and probable others once I get into it more.
ws
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