[amsat-bb] Re: Theoretical Question

Bryce Salmi bstguitarist at gmail.com
Mon Oct 14 00:57:20 PDT 2013

I found this paper:


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.


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
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