[time-nuts] HP 10811 update

[Bob Camp]

Hi

Well if you get desperate to try it, I have CO2 and a chamber sitting in the garage. The biggest issue is that if we use too much CO2 for the chamber, the beer may go flat…

Bob

On Jul 26, 2013, at 4:09 PM, paul swed <paulswedb at gmail.com> wrote:

> Bob
> I think the power bill exceeds the cost of a 10811. The chamber and CO2.
> Going to pass.Though I am sure I can run down to work and throw a unit in
> the various walk in units we have. Suspect they will not appreciate me
> adjusting the temps though.
> Back to work as they say.
> Regards
> Paul
> WB8TSL
> 
> 
> On Fri, Jul 26, 2013 at 3:53 PM, Bob Camp <lists at rtty.us> wrote:
> 
>> Hi
>> 
>> Tossing a nice fluffy towel over it works pretty well. Just the thing if
>> you are doing a bench turn hunt on an AT based OCXO. It's also a quick way
>> to answer the age old question "is it broke or is it just all the people
>> walking by while I'm trying to test it".
>> 
>> You need something that will let you go say 25C 5C 25C 45C 25C. Each time
>> you make a change and re-test, you want to run the same temperatures. You
>> need enough air circulation (and proper ducting) so that the device OCXO
>> stabilizes quickly. 300 to 600 CFM is the range most chambers run in. Dead
>> air = hard to know what temperature you are at / large delta T within the
>> chamber. A dwell of maybe an hour at each one is about right. A Tenny Jr is
>> a pretty good chamber for home use (no CO2). Keeping the refrigeration
>> repaired can be a chore though…
>> 
>> Bob
>> 
>> On Jul 26, 2013, at 3:33 PM, paul swed <paulswedb at gmail.com> wrote:
>> 
>>> So laying a sock over the insulated oven can doesn't count? Its a thick
>>> sock.
>>> Still not at the stage of needing a chamber I am 45 Hz off.
>>> 
>>> 
>>> On Fri, Jul 26, 2013 at 2:36 PM, Bob Camp <lists at rtty.us> wrote:
>>> 
>>>> Hi
>>>> 
>>>> Doing any real adjustment on these OCXO's pretty much requires you have
>> a
>>>> temperature chamber and a pretty good standard. A GPSDO will do for the
>>>> standard, the chamber is a bit harder to come by.
>>>> 
>>>> Bob
>>>> 
>>>> 
>>>> On Jul 26, 2013, at 1:38 PM, Rick Karlquist <richard at karlquist.com>
>> wrote:
>>>> 
>>>>> Ed Palmer wrote:
>>>>>> Hi Paul,
>>>>>> 
>>>>>> Did you see this page that talks about tweaking the 10811 oven
>>>> controller?
>>>>>> 
>>>>>> http://www.realhamradio.com/z3801a-turning-point.htm
>>>>>> 
>>>>>> Ed
>>>>>> 
>>>>> 
>>>>> Although this article anecdotally claims success, it overlooks
>>>>> a number of important issues.  First of all, a large proportion
>>>>> of 10811 crystals DO NOT HAVE A TURNOVER.  They merely have a
>>>>> very low TC around 82 degrees.  It is ALWAYS 82 degrees for these
>>>>> crystals.  The crystals that do, technically, have a turnover,
>>>>> still have very low TC even if the oven is slightly off the turnover.
>>>>> Secondly, the tempco of the electronics, specifically
>>>>> the selected 2N5179 oscillator transistor, is a significant player.
>>>>> The thermal gain, if properly adjusted, is around 1000 at the
>>>>> crystal, but is much less at the oscillator transistor.  It may
>>>>> very well be the dominant factor in overall oscillator tempco.
>>>>> Possibly, if you have a crystal with a turnover, you should
>>>>> deliberately operate off the turnover at a point where the crystal
>>>>> drift cancels the drift of the electronics.
>>>>> If you want to tweak a 10811, you should also tweak the thermal
>>>>> gain by custom adjustment of the heat balancing resistors for
>>>>> the heater transistors.  This has to be done by converting the
>>>>> oscillator to mode B and then converting it back to mode C
>>>>> afterwards.
>>>>> 
>>>>> Rick Karlquist N6RK
>>>>> 
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