[time-nuts] Re: HP 10811-60111 Oscillators {External}

[Jim Muehlberg]

John,

I'm beginning to understand that and indeed, the LTC mode appears more 
stable at shorter tau.  I am currently measuring using the network so my 
sample interval is maxed (min'd?) out at 0.12s due to network delay.  
But the trend I am seeing confirms your synopsis.  The environment 
probably is not stable, just an ordinary lab/office situation.  Right by 
the door too, just to make it interesting!

In the plot, the Purple is the spec for the opt 4 tube, the blue is the 
LTC mode, and the tan is the 1s mode.  The reference is another opt 4 
5061.  Condition of either 5061 is somewhat dubious, so all this may be 
garbage.  Coupled with the fact that I really don't know what I'm doing!

Jim


On 2023-01-11 2:31 PM, John Ackermann N8UR via time-nuts wrote:
> Hi Jim --
>
> Cesium standards aren't necessarily all that good at short tau as 
> virtually all use the Cesium transition to steer an OXCO in a phase 
> locked loop.  The short term stability can be only as good as the 
> OCXO, which dominates the stability within the loop bandwidth.  So 
> it's at longer tau, outside the loop bandwidth, that Cesium stands 
> out; the ADEV improves decade-for-decade as the measurement interval 
> increases out to a final noise floor.  And of course Cs has the 
> advantages of negligible drift, good retrace, and of course that it 
> defines the second (for now).
>
> The HP5061A had a switch between (IIRC) 1 and 60 second loop time 
> constants.  You could use the long mode to get better short term 
> stability, *if* you were in a stable environment, had a good Cs tube 
> and OCXO, and the stars were aligned correctly.  If not, the loop 
> would go out of lock at some indeterminate time and the alarm light 
> would go on. The 1 second time constant was much more reliable, but 
> noisier at short tau.
>
> John
> ----
> On 1/11/23 10:40, Jim Muehlberg via time-nuts wrote:
>> Bob, so the ADEV gets better than factory spec - better over time?  
>> The number stated below approaches NIST_F1 at 1s ~2.8E-13. (Not sure 
>> if its correct - found on a slide presentation) and apparently 
>> exceeds most commercial cesium clocks for time scales less than~10s..
>>
>> This is all fascinating since I now have two functional (as far as I 
>> know) opt 4 5061As (with, of course, 10811s inside). Plotting the 
>> spec for the 10811 and the 5061 in time lab is interesting, as the 
>> ADEV for the 10811A does indeed  exceed the 5061 for time scales less 
>> than 1s.
>>
>> Maybe this is old news to all of you, but it's more than I knew 
>> yesterday!
>>
>> Jim
>>
>>
>> On 2023-01-10 8:57 AM, Bob Camp via time-nuts wrote:
>>> Hi
>>>
>>> There’s a seller on eBay ( besttestus ) who comes up with batches of 
>>> 10811’s from who
>>> knows where. Some are still attached to option boards for 
>>> instruments. They just sold out
>>> of the latest batch of about 200 or so. I’d guess they will get some 
>>> back in eventually.
>>> Asking price is typically right around $50 or so (with free 
>>> shipping). They take offers so
>>> you can indeed get them to sell you 10 at a whack for around $42 each.
>>>
>>> Based on testing more than a few of them, there will be a couple 
>>> that have significant
>>> issues ( < 5%). There will be some that are in spec, but not by as 
>>> much as when they
>>> left the factory ( maybe another 5 %). The rest split into “pretty 
>>> good” and “really good”.
>>>
>>> The fact that the really good ones are still in the group suggests 
>>> that these are indeed
>>> NOS or something like that. A lot of batches you see have the best 
>>> of the best pulled out
>>> and you are just buying “the rest”. I’d guess that Fair is in the 
>>> same mode, you get the
>>> whole lot and can sort time as you wish.
>>>
>>> Just how many show up in the sub 6x10^-13 ADEV range varies a bit by 
>>> lot. To me,
>>> anything that’s in the parts in 10^-13 counts as very good. How many 
>>> would improve
>>> if you burned them in for six months or so, who knows….
>>>
>>> Bottom line: You probably do better buying closer to the source of 
>>> the surplus in a
>>> case like this.
>>>
>>> Bob
>>>
>>>> On Jan 9, 2023, at 4:18 PM, DM via time-nuts 
>>>> <time-nuts at lists.febo.com> wrote:
>>>>
>>>> To All,
>>>> Just a quick heads-up to anyone who might be needing, or just want 
>>>> one for fiddling with, Fair Radio Sales has a fair stock and a 
>>>> pretty good price for the HP 10811-60111 ovenized oscillators 
>>>> (https://fairradio.com/product/10811-60111/) . They are selling 
>>>> them (including the 05328-20027 support assembly) for US $79.00 each.
>>>> Both I have bought two of them and both arrived in like new 
>>>> condition, and were fully operational, and required only minor 
>>>> tweaking to bring them to 10.0000000 MHz after running for a couple 
>>>> of months. The attached 05328-20027 support board indicates that 
>>>> they were removed from the HP 5328A or 5328B counters.
>>>> Seems to be a pretty good deal for these well-aged oscillators.
>>>>
>>>> BTW, Fair Radio is also offering the 10544A oscillators for US 
>>>> $69.00. Both are described as "Tested for output may need adjustment."
>>>>
>>>> Cheers,
>>>> DaveM
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-- 

Jim Muehlberg
Senior Engineer

National Radio Astronomy Observatory
ngVLA Local Oscillator Lead

1180 Boxwood Estates Rd B-111
Charlottesville, VA 22903-4602
P 434.296.0270
C 434.422.2017
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