[time-nuts] Question about SoundCard stability?

Bob Camp lists at rtty.us
Wed Oct 13 07:11:32 EDT 2010


Hi

Should have been two out of three things ...

Bob


On Oct 13, 2010, at 6:58 AM, Bob Camp wrote:

> Hi
> 
> Controller cycling is often a result of one of two things:
> 
> 1) Resistance in the power lead 
> 2) Extra insulation / dead air
> 3) Internal controller issues
> 
> There are a few other possibilities, but they are remote enough that you are unlikely to ever come across them. There's no advantage to building a controller that's cycling. It was more likely a bug than a feature.
> 
> Bob
> 
> 
> On Oct 13, 2010, at 4:00 AM, Magnus Danielson wrote:
> 
>> On 10/13/2010 05:32 AM, Jim Lux wrote:
>>> 
>>> 
>>> On Oct 12, 2010, at 6:09 PM, Magnus Danielson<magnus at rubidium.dyndns.org>  wrote:
>>> 
>>>> Hi Bob and Dave,
>>>> 
>>>> On 10/13/2010 02:57 AM, Bob Camp wrote:
>>>>> Hi
>>>>> 
>>>>> Yes it is a reasonable expectation as long as you don't have a lot of drafts. A good TCXO can get down to sub 0.1 ppb over that period.
>>>> 
>>>> This is why I like ADEV plots in datasheets. I rarely get to see them. TDEV plots is a nice complement naturally.
>>>> 
>>>> Cheers,
>>>> Magnus
>>>> 
>>>>> Bob
>>>>> 
>>> 
>>> And I wish there were adev plots for cheap tcxo's on the mgr data sheets
>> 
>> Me too. I have to make the measurement myself. In one case I found that the oven control in one OCXO was unstable and had a resonance at about 7 second period. It was possible to measure it on the current supply too. The oven-control was having a relatively high-Q resonance and self-oscillation around the stability point. It increased the ADEV at that point to almost about 10 times more than expected. I learned that it was a good thing I measured it and yes, that spec didn't exist in the datasheet. It is unclear if they knew it or not. Even my half-crap setup proved valueable as I got aware of an issue on sample level rather than out in production phase.
>> 
>> Cheers,
>> Magnus
>> 
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> 
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