[amsat-bb] Re: Theoretical Question

[Bryce Salmi]

I found this paper:

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&ved=0CC4QFjAA&url=http%3A%2F%2Fmarine.rutgers.edu%2F~kerfoot%2Fpub%2Fslocum%2FRELEASE_6_32%2Fsrc%2Fdoco%2Fspecifications%2Firidium-phone%2FIR_Lband.doc.rtf&ei=U6NbUrCdCuakiQLXgoGwAw&usg=AFQjCNHpZ7_Jh9hNlGLTvRbkVi2o7ancYQ&sig2=bC2RkaZCSpODi-QVR7z2mA&bvm=bv.53899372,d.cGE

Which seems to state that the subscribers of Iridium communications (the
handset) adjust for Doppler shift. Each satellite is spaced such that there
is also a "guard band" so they don't interfere with each other.

Bryce


On Sun, Oct 13, 2013 at 6:55 PM, <lucleblanc6 at videotron.ca> wrote:

> On 13 Oct 2013 at 18:30, Dave Marthouse wrote:
>
> > This isn't a question regarding amateur satellites but it is an
> interesting
> > theoretical one to pose here and the same laws of physics apply.  I know
> > that the higher the frequency that is transmitted from a satellite the
> > larger the Doppler shift will be.  The Iridium satellites transmit at
> around
> > 1.5gHZ.  At that frequency I know the Doppler is large.  How do they
> manage
> > to keep the portable handsets on the ground locked to the signal?  Are
> the
> > handsets frequency agile to an extent?  How do they achieve frequency
> lock
> > so that the digital signals are decoded?
> >
> >
> >
> > Dave Marthouse N2AAM
> > dmarthouse at gmail.com
> >
> Interesting question Dave
>
> I suspect as the XM/SIRIUS radio a data signal is sent back to the
> receiver position to minimized the doppler effect and some sort of data
> error correction also help to counteract the doppler effect. A similar
> system is implemented into the wxtoimg NOAA weather satellite fax
> decoding software.
>
> It is an educated guess who only need to be reeducated... Lets say my
> Sirius receiver in a plain flat field suffer some signal breaks that
> i can't explain.
>
>
>
>
> Luc Leblanc VE2DWE
> WAC BASIC CW PHONE SATELLITE
>
>
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