[time-nuts] Timing Distribution in Mountainous Terrain
magnus at rubidium.dyndns.org
Sat Sep 11 10:35:06 UTC 2010
On 09/10/2010 07:17 AM, jimlux wrote:
> Ralph Smith wrote:
>> On Sep 9, 2010, at 8:01 PM, Rick Karlquist wrote:
>>> I would like to point out that the environmental sensitivities of
>>> the 5071A are unmeasureable, and the measurement threshold is
>>> far below 5.8E-14. I would estimate that the 5071A (and ONLY the 5071A
>>> among commercial clocks) could get the job done provided that you could
>>> compare its frequency to GPS to the stated accuracy. This would
>>> be using the 5071 as a secondary standard. You still need to
>>> deal with the short term stability of the 5071A, depending on
>>> your system needs. JPL uses H masers as flywheels.
>> I would imagine the cost of a 5071A per radio station would make the
>> check writers swallow hard, and adding an H Maser into the mix would
>> really get their attention. Especially if you need redundancy.
> there's also the possibility mentioned earlier of using a lower quality
> standard at each station and flying (driving) a higher quality clock
> (5071) around often enough to keep them trued up.
> If it's far enough in the future.. Hg ion traps have a lot of
> potential.. smaller, lower power, etc. than Cs
Commercial availability is somewhat limited. A problem with Hg ion traps
would be ROHS, unless they can be exempted or assumed to be within the
telco exempt, which would be a legal twist on the commercialisation aspect.
Another aspect I have been wondering about is the trap hold-length, I
think I recall that there was some issues relating to that...
> I think, though, that some sort of self calibrating array using the
> target of interest is a better scheme.. multiple receivers at each site
> separated by some distance. Getting milliradian angular resolution is a
> piece of cake.
That moves the expense, and I don't think the available receivers have
that option. They intend the spatial separation to be in kms and not m.
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