[time-nuts] Looking for datasheet for Oscilloquartz 8602

[Bob Camp]

Hi

On Jun 1, 2013, at 12:04 PM, Attila Kinali <attila at kinali.ch> wrote:

> Moin,
> 
> On Sat, 1 Jun 2013 11:21:44 -0400
> Bob Camp <lists at rtty.us> wrote:
> 
>> The electronics in an SC based OCXO will be different from the "stuff"
>> in an AT based part. At the very least you need additional traps for the SC.
>> You also need to do something to accommodate it's significantly higher
>> resistance. On the plus side, the SC probably can take 4X higher drive than
>> the AT for a given amount of delta frequency / delta drive. Again, something
>> that will impact the circuit. 
> 
> Oh..right. Didn't think about this (although i just read it in Vigs tutorial).
> While we are at it. Is there any good resource (book, webpage, papers)
> on the different crystal oscillator circuits and their advantages and
> disadvantages? I couldn't find anything usefull but a few general circuits
> (mostly from RF and ham radio books).

There's not a lot of information in the public domain. 

> 
>> Far more significant than any of that - marketing may well have asked that
>> the part be optimized in a different way so it would sell better. Phase
>> noise often seen as a better "bragging rights" spec than ADEV. My personal
>> opinion is that this bias is driven more by the fact that fewer people
>> understand (or trust) ADEV and it's derivatives. 
> 
> Could you explain a little bit more about ADEV vs phase noise?

Both ADEV and phase noise are measures of how perfect (or imperfect) a signal source is. One is a frequency domain measurement (you can see it on a spectrum analyzer). The other is commonly thought of as a time domain measurement (since tau is in units of time). My observation is that customers are much more likely to specify multi point phase noise than ADEV. You are much more likely to see big font stuff in ads talking about phase noise than ADEV. 

Both suffer from people talking about levels (-120 dbc or 1x10^-11) without mentioning the offset or tau. Since both are highly dependent on the offset or tau that's not a good thing. My observation is that ADEV is much more likely to be mentioned without an associated tau than phase noise without an offset . I've also observed that when the error is mentioned you are likely to get a "oops I'll fix that" on phase noise. On ADEV people often simply don't get the fact that tau matters even after it's pointed out. 

Looking at what the systems using OCXO's are actually doing, about half the time ADEV is probably the better  / more important measure than phase noise. The system is more sensitive to the OCXO wandering around over 100 or 1000 seconds than it is on the level of a sideband offset how ever many Hz off carrier. Once you get past ADEV, you rarely see an OCXO specified for any of the other related specifications. That's a shame, since some of them are better measures of certain things than ADEV. Again, I blame the fact that people just don't understand / trust the measurements. 

Bob

> 
> 			Attila Kinali
> 
> -- 
> The trouble with you, Shev, is you don't say anything until you've saved
> up a whole truckload of damned heavy brick arguments and then you dump
> them all out and never look at the bleeding body mangled beneath the heap
> 		-- Tirin, The Dispossessed, U. Le Guin
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