[aprssig] Terrestrial Threat to GPS Has Now Hit The Manstream Media

[Wes Johnston, AI4PX]

Bernard, the "jammer" is a new neighboring data service that may be deployed
nationwide in the USA.  It is a very big deal since GPS units in the past
(and presently) do not have any decent filtering on their front ends.  It's
very possible that this service could render a normal run of the mill GPS
useless within a km or so of the data site.    Even the cheap GPS units can
be effected by a cell phone as far as 300mhz away.  It is a GPS problem, but
there are so many out there... Kinda like garage door transmitters were
licensed as secondary years ago, and ran the primary off the frequency due
to their sheer numbers.

Wes
---
The world needs more geniuses with humility because there are so few of us
left.



On Sun, Apr 10, 2011 at 13:52, Bernard Van Haecke <
bernard.vanhaecke at gmail.com> wrote:

> This is a non issue unless the jammer is sitting on a sat or airplane.
>
> If terrestrial and uses high power, he will be DF'ed in no time.
>
> Otherwise, this story is a joke.
>
> Bernard
>
> Sent from my EVO android phone
> On Apr 10, 2011 10:44 AM, "Alex Carver" <kf4lvz at yahoo.com> wrote:
> >
> >> From: "Rahn Abbott"
> >>
> >> Ummmm, you do know that that US Military GPS units and your
> >> Garmin Etrex are
> >> not listening to the same radio signals right? You do know
> >> military and US
> >> government GPS runs on a completely different system?
> >
> >
> > No, the military listens to both L1 at 1.57542 GHz (the "civilian" GPS
> signal) and L2 at 1.22760 GHz, the military-only GPS signal. They use both
> signals in order to determine delays caused by the ionosphere which improves
> the accuracy of the military GPS receivers. If interference is caused to the
> L1 signal it will affect both civilian and military users.
> >
> > A military GPS receiver and a civilian GPS receiver both listen to L1 but
> they each use a different chipping code (civilian uses unencrypted C/A and
> military uses both unencrypted C/A and encrypted P). Only the military GPS
> receiver listens to L2 at the same time.
> >
> > Later on there will be new codes (L1C and M) as new satellites are put in
> orbit but they will still have both civilian and military codes sitting on
> L1. In addition, civilians will soon have access to L2 in the form of a
> civilian code on L2 (L2C) which will allow for some basic ionospheric
> corrections to improve accuracy and reduce drift. It won't be as accurate as
> the military receivers but better than the current L1-only receivers.
> >
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>
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