[time-nuts] HP 5061Cs reference question

paul swed paulswedb at gmail.com
Sat Dec 6 15:51:58 UTC 2014


Magnus
Great but I am looking for very specific detail. If you pick a wrong peak
especially if you can't see peaks on a very weak tube then I think that
translates into an actual offset.
If thats a true statement. Given the modern GPS boxes we have today that
are stable. Wouldn't you see that as a always constant drift. Say 7-10ns
over 20 minutes?
If you restart the system it magically comes back to the same offset.
Also there is a second harmonic reading and control. If you very the fine
phase on the 5 MHz indeed the ctl voltage readout adjusts and the system is
locked. Green light.
Here is the real issue the tube has always been so weak that you simply
can't look at the i meter and see humps. What I had done a long time ago
was add in another meter that was very sensitive and then use a magnifying
glass to see the peaks.

Regards
Paul
WB8TSL

On Sat, Dec 6, 2014 at 10:41 AM, Magnus Danielson <
magnus at rubidium.dyndns.org> wrote:

> Hi Paul and Bob
>
> On 12/06/2014 04:04 PM, Bob Camp wrote:
>
>> Hi
>>
>> Sure you can set them on the wrong peak. If you really get confused, you
>> can also set them on the wrong transition … (gulp).
>>
>> Peak wise, the one you want is the highest Q / best SNR. Set it to one of
>> the others and your ADEV degrades.
>>
>> Transition wise … not a good idea at all.
>>
>
> It's worse than that. Of the 7 peaks, the middle one has significantly
> least sensitivity to the C-field, as well as having the strongest response.
>
> The "new" digital cesiums actually measures the near-by peaks to sense the
> C-field and servo the C-field and then use the center peak for servo the
> frequency. This is a key to increase the stability of frequency and reduce
> a systematic effect.
>
> Cheers,
> Magnus
>
>
>  Bob
>>
>>  On Dec 6, 2014, at 9:11 AM, paul swed <paulswedb at gmail.com> wrote:
>>>
>>> I have a curious question that really applies to all Cs references.
>>> Its possible to set them on to the wrong peak.
>>> Typically in the literature it will speak to at least 3 peaks and you
>>> want
>>> to select the highest central peak.
>>> However if you select the wrong peak, how much would the output frequency
>>> be off?
>>> I had read a tech note for the airforce that seems to indicate its pretty
>>> easy to get on to the wrong peak.
>>> Regards
>>> Paul
>>> WB8TSL
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