[time-nuts] 5061 Cs frequency shift with long time constant?

Chuck Harris cfharris at erols.com
Wed Apr 6 14:11:16 UTC 2005


John Ackermann N8UR wrote:
> Thanks, Tom.  That's another excellent point.  The long term stability 
> impact of this cap is worth considering.
> 
> Following up on Brian's comment yesterday, I'm investigating sources for 
> very low leakage caps.  If I find some, I'll let the group know, and if 
> there's a minimum purchase quantity that's reasonable, I may just buy a 
> bunch and make them available to the group here.
> 
> John
> ----
> buehl wrote:
> 
>> John:
>>
>> If circuit has an electrolytic, following may influence how/ when you 
>> recalibrate.
>>
>> Electrolytics change value and leakage with no voltage applied for 
>> long periods.  So if the long TC cap has been switched out for months 
>> it will need a long time with "in circuit" to stabilize again.  The 
>> electrolytic barrier "forms" as a result of the electric field across it.
>>
>> Tom Buehl

Given the easy availability of mylar caps in the 1 to 10uf range, I highly
doubt that such an important task would be given over to an electrolytic.

-Chuck




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