I've had this exact problem. The SNR of GPS is very low and anything
will interfere with it. In my case, I had a power amplifier (PA) on the
same antenna mast as my GPS antenna. Both were filtered to their
respective bands. Because of other system parameters, I couldn't power
the PA off so I simply terminated its input into a matched load when I
wasn't using it. The noise generated by the terminated PA put enough
noise in the GPS band to block it, despite the filters. I ended up
connecting the PA's output to its antenna through an RF switch. When I
wasn't using the PA, I terminated both the Tx antenna and the output of
the PA.
So, filter the input of the GPS antenna, if you can. Buy a GPS that's in
a metal box. If you're transmitting, even far way from the GPS band, see
the above paragraph. Power down anything you don't need when you're not
using it. Maybe ignore the output of the GPS while you're using bits of
your system that you've seen interfere with the GPS..
Physical isolation (e.g. wrapping things in aluminum foild) is hard to
do repeatably and reliably. Antenna separation is definitely your friend.
Kevin
On 4/30/2019 10:33 AM, Charles West via TriEmbed wrote:
Hello from the North!
I'm still working on the golf course robot. Recently I've run into a
rather odd issue. When I put everything together for my 1/8 scale RC
car platform, my GPS module refused to converge. I spent a solid 4
days debugging it only to eventually discover that the problem
appeared to be that my USB 3 camera was putting out large amounts of
RF interference of a spectrum suitable to interfere with my GPS even
when there was a metal ground plane between the GPS and the rest of
the equipment.
Eventually, a combination of wrapping the camera in metal tape,
placing the GPS with a ground plane elevated way above the rest of the
robot and wrapping the camera's cable in aluminum foil finally got the
GPS to converge. The only problem is, the accuracy of the GPS is far
worse than in the previous version of the robot. Originally, I got
within a 2-3 meters with an occasional drift. Now it squiggles all
over the place.
Does anyone know what I should try next to get decent performance
and/or hunt down any interference for the GPS?
Thanks,
Charlie West
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