[time-nuts] Timing Distribution in Mountainous Terrain

[Magnus Danielson]

On 09/11/2010 05:29 PM, jimlux wrote:
>>> 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.
>
> that's for sure.. I think all the Hg ion traps are still laboratory
> curiosities.. but, 10 years from now?

Sure, but that assumes his target deployment is 10 years ahead.

> 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.
>
> And Cs or Rb don't have the same sorts of issues?

No.

http://en.wikipedia.org/wiki/Restriction_of_Hazardous_Substances_Directive

>> 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.
>
> I was thinking about changing the problem somewhat.

Yes, but now you shifted from "time-support system of transciever boxes" 
to modifications of the boxes themselves or at least use multiple boxes 
for angle determination only (wasting much of the rest of the receiver 
structure).

> You'd have your
> stations separated by km, but each station has several receivers and can
> compare the phase of the signals. You can solve for range rate (Doppler)
> and angle (delta phase), and that can go into your position solution.
> (this is how we navigate spacecraft, after all, and it's also used for a
> variety of target tracking systems)

Yes, yes... I understood perfectly what you where describing and no 
doubt such a hint would be most useful, but it may not be applicable to 
his problem. The question is really if he has complete boxes to build 
with or can alter their design. Additional delta-channels is best 
handled in a combined receiver, as being done in many other similar 
heading receivers... such as GPS receivers with angular orientation such 
as used in airplanes and on ships.

Cheers,
Magnus