[time-nuts] Need advice for multilateration setup
magnus at rubidium.dyndns.org
Fri Apr 3 07:12:27 EDT 2015
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.
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.
>> 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
>> 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.
>> Attila Kinali
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