[time-nuts] Agilent 53220A and TimeLab

[timeok at timeok.it]

Hi all,



On Wed 03/02/16 07:06 , "John Miles" <john at miles.io> wrote:

> Hi, Timothy --
> 
> > I've had an Agilent 53220A for some time, and recently discovered the
> > wonderful TimeLab software, but I've hit a bit of a snag trying to run
> some
> > ADEV measurements on a Rb clock. The problem is that the graph doesn't
> > line up with the amount of data TimeLab says is collected. I ran an
> > acquisition for 100 seconds, but according to the chart it only shows
> data
> > collected for 20 seconds....
> 
> See page 31-32 of the manual
> (http://www.miles.io/TimePod_5330A_user_manual.pdf). [1] I think you'll
> find it anticipates that very same question. :)
> 
> > On a side note, I was disappointed to find out that I missed the boat on
> > the semi-affordable TimePod. Is there anything remotely in the price
> rang
> > (sub 5K) that can do stability AND phase noise measurements? It seems
> like
> > the Wavecrest DST "might" be able to, but from what I read in the
> time-nuts
> > archive I wasn't able to get a clear picture.... there's an app note
> > floating around about making phase noise measurements with it, but
> > nothing
> > solid.
> 
> The Microsemi 3120A's price has come down a bit over time, so I'd suggest
> checking with them to see what the current pricing is like. (Obligatory
> disclaimer: I have no current financial/professional involvement with the
> 3120A.) I suspect it's still well north of $5K, depending on options, but I
> know they've stepped back from the initial prices they were quoting.


Unfortunately it  is very difficult to measure the Allan deviation levels to E-14 and beyond.
I have tried some solutions like Wavecrest and Dual mixer Time Interval but with poor results:

Wavecrest: 
He has a good resolution but not exceptional but its major limitation is the number of samples that can handle, he finished his memory and go in  times out, so you cannot perform long-term measures.

DMTI: 
Very critical and difficult to manage. The time interval between start and stop is proportional to its noise floor. As this parameter varies during the measurement based on the stability of the two sources, you cannot predict about Noise floor. Others critical conditions are, the temperature, the level of the input signals and the delay lines you have to use for the optimal TI is approximately between 50 and 300 uS. In addition, the phase wrap is still there because the delta-time due to the delta freq. It accumulates with each measurement up to the wrap (depend on the measurement time and Frequency difference).

Honestly I do not see at present practical solutions and reliable low cost.

Luciano
www.timeok.it

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