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

[John Ackermann N8UR]

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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