[time-nuts] Question about SoundCard stability?

Bob Camp lists at rtty.us
Wed Oct 13 10:58:02 UTC 2010


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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