[time-nuts] GPS Antenna -Receiver Mutual Interference...

[Arthur Dent]

Burt I. Weiner-
"Recently I've had need to operate with two GPS navigation systems in 
the same car at the same time and I've had to shield the antennas from 
each other, or at lease get them as far apart as practical on a car otherwise 
they both seem to interfere with each other and I can lose GPS lock."

If it were a problem with the GPS receivers I'd expect the receiver proximity
to be the factor and not the antenna separation. Right now I have a Garmin
60CSx and a Garmin 62s touching each other and sitting next to my inside window
receiving satellites without any problem. Most car antennas are just amplified
patch type antennas and there is a possibility that the coax from the antennas
don't have anywhere near 100% shielding and are re-radiating some of the 
received
signal and the other antenna is picking that up, causing the problem. I'd 
suspect
that it is the antennas and not the receivers. Some people have used this for a 
practical application for GPS receivers that don't have external antenna 
connectors
and made re-radiating loops for those receivers.
http://www.bytethebullet.com/geocaching/reradiating_antenna.htm

           -Arthur