[time-nuts] E1938A PN measurments

[Bruce Griffiths]

Bruce Griffiths wrote:
> Magnus Danielson wrote:
>> On 09/29/2012 02:45 PM, Bruce Griffiths wrote:
>>> For those that have Timelab the link to the E1938A PN measurement 
>>> data is:
>>>
>>> https://dl.dropbox.com/u/59708595/E1938A.tim
>>
>> Thank you. I will measure mine so that we can compare them.
>>
>> Cross-correlation with a pair of BVAs should do it.
>>
>> Cheers,
>> Magnus
>>
>>
> I'm still a little suspicious of the result, although measuring a 
> second E1938A removed from a Z3815A produced similar results.
> I'll measure one of them again with an isolation transformer to 
> eliminate an LF earth loop to see if the earth loop was an issue.
> Using a single reference (PN floor < -170dBc/Hz) should suffice for this.
> I didnt have RF isolation transformers available at the time.
> I have since found that using a single point LF ground (rather than 
> floating the entire interferometer) reduces the interferometer PN 
> floor substantially.
>
> Bruce
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to 
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
Measuring the E1938A with a single point LF ground produces 
substantially the same result.
A PN measurement using a different technique (classical mixer and low BW 
PLL) may be useful.

Bruce