[time-nuts] Need advice for multilateration setup

[Robert Watzlavick]

Thanks for the suggestion. Does the DSSS make it easier to correlate between ground stations?  I'm not sure how to handle the phase offset on the 10 MHz ref clocks. 
-Bob


> On Mar 26, 2015, at 07:25, Attila Kinali <attila at kinali.ch> wrote:
> 
> On Wed, 25 Mar 2015 21:27:35 -0500
> Robert Watzlavick <rocket at watzlavick.com> wrote:
> 
>> I'm working on a project that I could use some advice on and also might 
>> be of interest to the list.   If it's not appropriate for the list, my 
>> apologies.
> 
> The gods have apporved of your request. You may speak now.
> ;-)
> 
>> I want to develop a tracking system for an amateur rocket that can allow 
>> me to track the rocket even if onboard GPS is lost (as is typical during 
>> ascent and sometimes during descent) or if telemetry is lost.
> 
> Given you can synchronize the clocks of the ground stations well
> enough, then the rest is "easy". Then you can get away with having
> a simple signal generator that only needs an XO. Or you can go
> for a TCXO to make your signal processing life easier.
> 
> What you need to do, is actually the same as GPS does: Create a
> direct spread spectrum signal and track it on all ground stations.
> The DSSS has the advantage over the single pulse, that it's more
> resilient against noise and interference. The disadvantage is, that
> you have to have more complicated hardware. One viable way would be,
> that you have precisly synchronized sampling systems (e.g. SDR's like
> the bladeRF which can take an external clock) and then feed the data
> to a PC where you do the heavy lifting. Then you don't need to build
> custom hardware at least.
> 
> Also, if the precision by the DSSS signal is not good enough, you can
> apply various tricks from the GPS world, like carrier phase tracking, etc.
> 
> HTH
> 
>                Attila Kinali
> -- 
> It is upon moral qualities that a society is ultimately founded. All 
> the prosperity and technological sophistication in the world is of no 
> use without that foundation.
>                 -- Miss Matheson, The Diamond Age, Neil Stephenson
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