[time-nuts] Need advice for multilateration setup

[Magnus Danielson]

Remember that you can actually let each base-station transmit at a 
different code, and you can then monitor them that way. You could even 
keep them frequency and phase locked or just monitor it and adjust it in 
the post-processing. Such an approach would be a nice complementary 
solution to the GPS/GNSS receivers. Also, it's "more of the same" which 
helps in knowing your system.

Cheers,
Magnus

On 03/26/2015 06:32 PM, Robert Watzlavick wrote:
> 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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