[time-nuts] Need advice for multilateration setup

Jim Lux jimlux at earthlink.net
Mon Apr 6 09:09:41 EDT 2015


On 4/6/15 2:14 AM, Attila Kinali wrote:
> Moin,
>
> On Fri, 03 Apr 2015 22:51:34 -0500
> Robert Watzlavick <rocket at watzlavick.com> wrote:
>> On 04/03/2015 10:12 PM, Robert Watzlavick wrote:
>>> I have an amateur radio license (mostly CW/HF and some VHF/UHF
>>> experience) and I've written some driver software for an IQ
>>> demodulation board but I have to admit, I would have no idea how to
>>> begin setting up that system as initially described by Attila and
>>> expanded by you and others.  I have a rudimentary understanding of the
>>> modulation schemes involved but I don't fully understand how the
>>> various codes mentioned fit in. I've poked around a bit at some
>>> articles on PN codes and I can see how data would be transmitted but I
>>> think I'm missing something key that allows you to extract positions,
>>> velocities, etc. out of the various links.  I think I have some more
>>> reading to do :)
>
> The basic system is that of an DSSS modulator/demodulator.
> The best text on spread spectrum systems I have found sofar
> is [1]. I explains modulation and demodulation in a hands on
> fashion. But, due to the age of the book, it does not contain
> any of the advanced stuff done today. But I think you don't need
> anything more fancy than an early-prompt-late correlator architecture
> for tracking.

Actually, if you're post processing, you can just record raw bits and do 
the correlation in software.  You don't really need to track it in real 
time.  Although, that might not be a bad way to do it.







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