Michael Williamson
wrote:



Cub Driver wrote:

as long as the GPS is working. But it's a low-powered signal from orbit
and it's easily jammed.


How true is this, really? In an aircraft, you are between the ground
and the satellite. How does someone on the ground interfere with the
signal?


I don't believe that the antenna for the GPS is directional enough
that someone off axis couldn't put a signal into your system- after
all, a single antenna is used to pick up every satellite above the
horizon.

Mike Williamson

While this is true (the receiver antennas need to be and are
omni-directional) the satellites broadcast on ~1.5 gigahertz
therefore are very much 'line-of-sight' so any interference must
be transmitted within 'line-of-sight' to the 'interferee'. IOW,
to block a gps receiver you gotta be relatively close to it when
you're on the ground...if you're inflight then....you know...
--

-Gord.