[time-nuts] Equipment question: OCXO versus GPSDO + XTAL

Bob Camp lists at rtty.us
Fri Mar 18 11:41:11 UTC 2011


Hi

Do you need 20 ps resolution / accuracy? If so at what time spans or gate times?

If the answer is > 100 sec then don't bother with any of the options you mentioned. They are not good enough. Plan on getting a Hydrogen Maser. It is the only thing you can easily get with adequate stability. If traceability is needed at the same level, that would need to be adressed as well. 

In the .01 to 10 second range the OCXO provides a lower noise floor than the TBolt. The TBolt provides better accuracy.

At 0.001 seconds your 20 ps is 2x10^-8. The OCXO may not have an advantage over the cheaper internal standard at this point.

 AVAR is not absolute error. That is the data most commonly seen on oscillators. Translating to absolute error is not simple. Thus the somedwhat general answers.

Bob


On Mar 17, 2011, at 11:41 PM, Mark Spencer <mspencer12345 at yahoo.ca> wrote:

> I'm inclined to agree.   (I'm not sure I'd want to use my Thunderbolt as the reference oscillator for an instrument that had 20 ps of resolution, nor would I trust the long term accuracy of an ocxo without being able to compare it to a reference such as an gpsdo.)
> 
> 
> 
> Sent from my iPad
> 
> On 2011-03-17, at 7:30 PM, "J. L. Trantham" <jltran at att.net> wrote:
> 
>> Personally, I would get both.
>> 
>> Joe
>> 
>> -----Original Message-----
>> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
>> Behalf Of J. L. Trantham
>> Sent: Thursday, March 17, 2011 9:24 PM
>> To: 'Discussion of precise time and frequency measurement'
>> Subject: Re: [time-nuts] Equipment question: OCXO versus GPSDO + XTAL
>> 
>> 
>> Depends on what you want.  Stability or accuracy?  Bench or portable?  The
>> TBolt or another GPSDO will certainly be accurate.  Probably fairly stable
>> as well.  However, if you need portability, the OCXO is the only way to go.
>> You will have to look at the stability measurements of the OCXO versus the
>> GPSDO to choose that one
>> -----Original Message-----
>> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
>> Behalf Of Wolfgang
>> Sent: Thursday, March 17, 2011 8:51 PM f 
>> To: Discussion of precise time and frequency measurement
>> Subject: Re: [time-nuts] Equipment question: OCXO versus GPSDO + XTAL
>> 
>> 
>> On Friday 18 March 2011, Greg Broburg wrote:
>>> I have a 53131 and 53181. There were several TB options.
>>> I dont have a manual for the 53230A. If you could, see what the option
>>> TB assembly PNs are, then go looking for these assemblies. Mine just 
>>> dropped in and did the autocal right off. I paid 300 to upgrade the 
>>> 53181. The autocal using a DAC works very well, no more tweaking Rs or 
>>> Cs and waiting a day for them to restabilize.
>>> 
>> Don't recall where I read this but IIRC: 
>> 
>> There are several other options for the 53230A which can be added lateron 
>> by the user ("kits") but the OCXO can only be installed lateron by sending 
>> the device to service. 
>> 
>> Thanks to the list for the answers - but: 
>> 
>> It seems like everybody is telling me "go for the cheaper, add the OCXO 
>> lateron if you need it" - but that's not what I'm after. What I'd really 
>> like to do is to make up my mind based on educated opinions on this list 
>> whether the built-in OXCO option offers any advantage at all compared 
>> to standard clock + good external reference. 
>> 
>> - Wolfgang, DL1SKY
>> 
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