[time-nuts] HP 5065A performance vs. others
rfnuts at arcor.de
Mon Mar 22 00:05:30 UTC 2010
And, perhaps the OCXO contributes quite a bit, too.
I don't think the cheap X-tal oscillators in the small boxes are as good
as a 10811A in terms of phase noise etc...
Also, the buffer amps might be not as good as the 5065A ones. At least I
remember having observed significant frequency changes caused by load
After some 1 1/2 years of continous operation of my 5065A, I could't
measure any difference to my 5061A, even after averaging over 1 hour of
The FRK however suffered from massive runaway after plugging it in the
John Miles schrieb:
>> -----Original Message-----
>> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
>> Behalf Of Bob Voelker
>> Sent: Sunday, March 21, 2010 1:59 PM
>> To: time-nuts at febo.com
>> Subject: [time-nuts] HP 5065A performance vs. others
>> As several postings have indicated, the performance of the HP
>> 5065A is better
>> than many of the other rubidium standards. What enables the HP 5065A to
>> achieve better performance?--Is it the physics package or the particular
>> control system implemented in electronics? Would it be possible to
>> achieve the HP 5065A's performance by modifying a more commonly
>> available rubidium such as the LPRO? Would an ensemble of LPROs
>> match a single HP 5065A in performance?
> I think those are all open questions, because it's not immediately clear
> what limits the performance of the smaller telecom-grade physics packages,
> or what low-hanging fruit might be left on the tree.
> For instance, how important is the length of the path the light takes
> through the filter cell and/or resonance cell? It's obviously a lot longer
> in a 5065A. Or is it HP's proprietary buffer-gas mixture that makes most of
> the difference? Is there something special about HP's lamp? Is their
> microwave synthesizer that much better?
> HP's temperature stabilization is better than the LPro's -- so maybe it
> would help if you just moved the LPro's Rb assembly into an outer oven,
> separate from the rest of the electronics. How important is all that
> mu-metal shielding on the 5065A, given that most people these days would
> care more about stability than absolute accuracy (thanks to GPS)?
> Someone with more free time should tackle these questions. :) F. G. Major's
> book would be a good starting point, and this paper on laser-pumped Rb
> clocks also has a lot of hints about what limits the performance of ordinary
> sources: http://tf.nist.gov/general/pdf/1219.pdf . They used the cell from
> a commercial Rb standard in their experiment, although they didn't say which
> one. If nothing else, you can infer from this paper that the path length
> through the resonance cell isn't a huge deal.
> -- john, KE5FX
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