[time-nuts] iGPS?
Bob Camp
kb8tq at n1k.org
Tue May 19 21:33:50 UTC 2015
Hi
The Iridium frequencies are even further “up band” than the Glonass signals. None of the
“GPS” antennas that I have tried work very well on Glonass. I doubt they would do well
at all trying to get Iridium.
Bob
> On May 19, 2015, at 1:57 AM, David I. Emery <die at dieconsulting.com> wrote:
>
> On Mon, May 18, 2015 at 09:52:03PM -0700, Jim Lux wrote:
>
>> Why iridium? Why not Sirius or XM or DBS. Unless you want something
>> world wide, as opposed to "populated areas served by broadcast radio and
>> TV"
>
> Well it seems to me I remember Iridium is time domain duplex
> around 1610 MHz or thereabouts... which isn't too far from the L1
> civilian GPS at 1575.42 and quite possibly inside the bandwidth of
> some civilian L1 LNAs and antennas.
>
> Sirius XM is not that close at 2320-2345 Mhz.
>
> And inside its spot beam the Iridium signal is quite a bit more
> powerful and coming at one from constantly changing angles... whilst
> the Sirius XM birds are either geosync or in Molninya orbits and don't
> move much over short intervals - as does an Iridium signal.
>
> And of course (for the military especially) it IS worldwide and
> not just restricted to NA (where such an anti-jam capability is less
> useful at least at the moment). Something that works world wide
> is of course what the military folks need.
>
> And I suspect timing can be derived from the satellites TDD
> and message timing pretty easily if that is accurately synced to some
> reference...
>
> Others more familiar with the details may comment here...
>
> --
> Dave Emery N1PRE/AE, die at dieconsulting.com DIE Consulting, Weston, Mass 02493
> "An empty zombie mind with a forlorn barely readable weatherbeaten
> 'For Rent' sign still vainly flapping outside on the weed encrusted pole - in
> celebration of what could have been, but wasn't and is not to be now either."
>
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