[time-nuts] Making a HP 10811 better

[Neville Michie]

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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