[time-nuts] Re: Low Phase Noise70 10 MHz bench signal source sought

[Lux, Jim]

On 4/2/22 9:42 AM, Tom Van Baak wrote:
> Yes, I believe hp did what you propose in their Santa Clara cesium 
> test lab. It was an ensemble of selected 10811 oscillators tightly 
> phase locked to improve short-term stability and phase noise. Rick 
> might know the details.
>
> During a tour I saw the instrument rack but was unable to peek inside. 
> Performance details were not given and I didn't get to count the 
> oscillators but I think it was on the order of half a dozen. I figured 
> that using 2 or 3 probably isn't worth all the effort. And using ten 
> or more is diminishing returns or maybe beyond requirements.
>
> You can imagine if you were allowed to select the best of the best 
> 10811's as they came off the manufacturing test line and then combined 
> a bunch of them as they did, the results would be quite impressive.
>
> If you develop a board for this I think it would be of interest to a 
> number time-nuts. It merely takes time to measure each oscillator in 
> the pile and pick the best ones. But combining them takes the tricky 
> circuit design that you are planning. Please keep us informed of your 
> progress.


I wonder if there would be a clever way to do the measuring in parallel. 
(other than using N(N-1)/2 TICCs to do an N cornered hat of some sort)

(or N TICCs, if you're just looking to get rid of really bad ones, and 
you're comparing against your "house" standard)



>
> The concept of replicated simple electronics reminds me of:
>
> http://phk.freebsd.dk/raga/


Allan also had a scheme: "This is accomplished by using an ensemble of 
inexpensive oscillators, such as TCXOs or MCXOs."

D. W. Allan, J. A. Kusters and C. E. Wheatley, "CTXO, clever time 
crystal oscillator (clock),"/Proceedings of the 1999 Joint Meeting of 
the European Frequency and Time Forum and the IEEE International 
Frequency Control Symposium (Cat. No.99CH36313)/, 1999, pp. 354-357 
vol.1, doi: 10.1109/FREQ.1999.840780.


https://ieeexplore.ieee.org/document/840780

>
> /tvb
>
>
> On 4/2/2022 12:21 AM, ghf at hoffmann-hochfrequenz.de wrote:
>> I still have this idea to lock a flock of MTI-260 (which I have) to a
>> common Lucent-GPS, slooooowly to keep them as independent as possible,
>> but in-phase.
>>
>> Say 8 or 16 pcs. The outputs would be Wilkinson-ed together, so 2**n
>> oscillators are preferred. The phase noise should average away.
>> That's what my VTOCXO ctl board was originally for. It can do much more,
>> like local 1pps that is not needed here.
>>
>> Seems costly, but the last few dB are always costly. Should fit a 3H 
>> 19" box,
>> and the parts are available NOW and not next year.
>>
>> And, a 9 or even 17-cornered hat, has that been done?
>>
>> Gerhard,
>>
>> who loves replicated simple electronics like my 220nV/rtHz amplifier 
>> with 20 * ADA4898.
>>
>> Lockaflock (TM)
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